Yamaha XT600E 3TB - cold starting problems
 

Hello !

This is my first post on the forums and I will like to say hello to you guys !

I have the pleasure to ask you a few questions regarding my beloved 3TB from 1993.

There is a small problem starting when cold recently (since the weather dipped bellow 10 degrees Celsius).

The bike turns when I use the electric start it starts after 2-3 seconds and the revs don't climb and it eventually dies out on me. After 2-3 attempts like this the bike eventually starts (the revs climb slowly then a bit faster and reach the rpm it should be with the choke fully engaged) and from there on I have no problems. (I start it once in a week or two)

Things I've tried so far:

- I played with the pilot jet adjustment screw (from 2.5 turns to 4 turns out - no improvement on starting).

- If I try to adjust the pilot jet screw when the engine is warm I sense a small raise in rpm from 2.5 turns out towards 3 turns out the it flattens out (no more increase in rpm) I didn't screw it our further than 4 turns since the bike was running to rich according to my assumptions ...

- I've changed the spark-plug with a new one and charged the battery (it was bought new in summer and my charging system is in working order)

- I've used some carburetor/injector cleaner in fuel with no visible results

- The engine was rebuilt last summer including the following - cylinder honed ,new piston,new valves,new timing chain,etc. The valves were adjusted again after 500 km and they were lapped and checked for leaks when I've mounted them.

In summer I felt it was a little lean at idle and off idle (few pops on the exhaust while decelerating and when fast revving from idle). So I've enriched the idle mixture from 2.5 turns out to 3 turns out and the problems was solved... the bike returned to idle quicker with no popping.

A mechanic set the clip for the needles on middle position on both carbs and I've adjusted the transition mechanism between the carbs. (the transition is very smooth)

The spark-plug that came out soon after the issues became more prominent was black with carbon deposits. I think the bike is too rich on the needle since this guy "had to" move the clips to middle position on both needles but this doesn't explain my problems starting since the needle / main jet is not affecting starting of the bike.

What is the default (factory setting) for the needles and for the pilot jet screw ?

For pilot jet screw I've found on the forum that is 2-2.5 turns out (and Aukeboss says 4-6 turns out which I think would be too rich) and for the needle in the primary and secondary I'm not sure about clip position.

Again the bike turns over 2-3 times and starts but the rpm drops (engine dies) or it climbs very slowly to idle speed that should be with the choke engaged.

Also when the engine is at running temperature if I engage the choke it tends to die then it clears out and the rpm raise ... This sounds too rich ? but hard to start ? A lot of controversy going on in my head right now.

Please help if you have time !

Thanks,

Bernek

I can add a few pictures of the spark plug (sadly it does have some dirt on it after was taken out)

https://s18.postimg.org/c4vp24ofd/IMG_0166.jpg

The idle screw adjustment was around 3.5-4 turns out but I would blame it on the needle. I also have a bad habit of firing up the engine once a week and don't ride the bike. I know this is not a good idea but I can't help it ...

Hi Bernek and welcome to the forum.
If you aren't already doing so, drain the carb if you are not going to use the bike for more than a week. That will make starting easier.

Bob

I have same model, idle screw 2,5turn out and never any problems starting or idle. I had problems with carb before cleanup, it was the small filter inside with full off dirt making it. So yes remove carb and check filter, and the boots from carb to engine.

Thank you for posting ! I was curious why the drain plug screw shows evident signs of usage over time.

I will drain it when I'm not going it to use it for more than a few days. What is the tehnical explanation for this ? Fuel degradation ?

Regarding my starting problem:

I lowered the idle speed (as much as I could) and it seems to start a little easier now.

I'm at 3.5 turns out on the pilot jet screw and the firing and idle is better ! Will have to check tonight with the engine completly cold to see if I'm 100% right about it.

The boots are like new and the rubber is really holding good (I think they were changed recently 1-2 years ago before I purchased the bike).

The small filter I cleaned it maybe 6 months ago but I will remove it completly and install an inline filter on the hose. Any recommendations on this filter ?

Thanks for trying to help me out !

Bernek

L.E. the carburetors were cleaned using carb cleaner and compressed air in summer and I also used a carb repair kit for this model to change all the bits and pieces that are user serviceable.

I will have to solder a small screw on the pilot jet screw so I can adjust it easier... just need to find a brass screw with the same proportions. I hate burning my hands each time I'm trying to adjust this one.

Any settings for needles that you might share ? as I've stated the "mechanic" had to move them to middle position and I don't really like the spark-plug coloring that I had ... the photo is from the spar-plug that I've used maybe 1-2 months and it has close to 1000 km on it (mostly off-road). Is carbon build up really fast on these big singles ? Since the bike idled some time before I took this spark-plug out ...

No i dont have any build up on the spark its normal colour, honestly i dont remember the original settings on needle. I changed to dynojet kit, did you buy original or cheap china kit for carb? What size of jets do you have? Search forum, its all in here we have talked bout same problem before so i think you will find jet setting. If you dont find let me know, i have another original i can open and check.

The kit was not made from Yamaha but from another company (I can't remember the name) but the price was similar to an original kit. No way it was dirt cheap like chinese kits.

I think I payed close to 100 EUR for the entire kit. Chinese go for 10-15 GBP on ebay.

Regarding the needle position I searched in past (on this forum) but couldn't find something stated clearly. Just when you have time would be nice if you can check the original positions (so I can have a solid start in tuning).

I will try to start the bike again tonight to see how it will fire. I also have some doubts regarding the battery ? Since it transistored (TCI) it can't work without a battery and I might get a weak spark from an old battery ? Mine has 6 months and it was bought in spring 2017.

This is the battery that I use.

And with that weak spark and cold engine it could behave like I'm experiencing ? :helpsmilie:

It seems to me like this carb doesnt have been adjustet, but cant be sure. The diaphragm was 3notch, spacer and plastic under, remember to have hole free for the breathing in it.

So secondary (vacuum type) is 3rd notch.

Primary carb ? what position for the clip ?

Also 3rd notch you count from top (blunt end) ? Needle in working position I count 1-2-3 and on the 3rd that is middle position ? I think it has 5 positions.

Thanks a lot !

Slow down man i have take it apart first ;) yes both was the same place, center of the pin. 3rd from up or down its the same. Anything else?

No ! Thanks a lot for the information. So the middle position is the starting point.

Great news :) I don't have to take them apart yet.

Ok, you have align them correct for the opening?

Yes the transition is nice no problems there ...

Only the starting problem ... Engine fires after 1-2 attempts but it slowly dies ... after 2-3 more tries it fires and the revs climb and it works perfectly afterwards ...

Could this be a weak spark ? Should I change the battery ? I will measure the current when starting to see how low it drops !

Cheers,

Bernek

Why dont you charge the battery? Its normal that the bike can die after starting and then have to start again if it has been standing for some days, do you pull throttle when it starts or just waiting to see what happens?

I charged it already and after each use I put the trickle charger on it.

I just wait and and see sometimes I tried give it some gas to clear up and it started after 1-2 attempts. But it’s definitely not leave it for a week and start first time .... it needs 3-4 attemps (some firing some not) to have it started!

I don’t like this condition because these small batteries can run out of juice after a few failed attempts...

If your battery cant do more than 3 starts you need to replace! Here is best way to start:

1. Always turn petcock off, and best is to let bike idle till it stops and carb is empty.

2.When you start bike hold throttle a little and when it fire up keep holding throttle same position, you then hear when idle is good and it will run on the choke.

I have had bike standing for 6months and it fires up after seconds on the starter, but you need to help it a little and dont rely on the choke in the beginning. Turn the screw in not hard but just so you know its in, and then 2,5 turns out. I use a drill bits and mark it so its easy to know turns. I think maybe you chasing a ghost here...

Pretty sure both needles is in the 3rd (middle) slot stock.

You can raise the neelde in the main carb (left) a notch, that will provide more fuel, even at idle, and it should start better when cold.
You can shim the needles aswell, with small washers, to raise the needle half a notch. Shims from airsoftguns work great for this, and they come in really small increments.

However, if the carb is clean, the "right" way would be to change the idlejet to one size larger.

But its really easy to just alter the height of the needle. I can do it in about 10min, without removing the carb. So its well worth a shot.

Btw, I've had great succes with the cheap chineese carb rebuild kits on ebay, they're pretty complete with jets, needles ect.

How is it possible to change the clip position without taking the carbs off the bike ? I have to look for a way :)

If I raise the needle I should set the pilot jet screw to 2.5 turns out ? (default).

If I turn the pilot screw open 4.5-5 turns the mixture is too rich and it bogs during acceleration from idle ... how is the needle going to help ? The mixture will be even richer ?

So you say that my hard starting is because of a lean condition ? I tested with the pilot screw 2 turns towards 4 turns out and starting is almost the same.

Please share with me how can I adjust needle clips without removing the carbs so I can give this a try too :)

Thanks !

If these two screws are accessible with the tank removed I can do it also :D

https://s18.postimg.org/5ijlmznll/carb.jpg

Not sure have to check :)

It's a royal PITA to mess with that needle with the carbs still on the bike , You have to take the whole mechanism out to get to the needle and there is a spring under it ect...... good luck getting it back in while on the bike . I've done it but in more time than just removing the carbs.

For starting and choke use something that everyone overlooks is the tube for the choke goes down into a hole in the left carb bowl. There is a small hole for the fuel to flow into that spot from the bowl that gets plugged easily and is hard to get clear. When you have the carbs off take the bowl off and make sure all those little passages are clear. I go up one size pilot jet on my bikes for winter and turn the mixture screw out about 1 turn farther , we don't have adjustable needles so not much can be done there other than one thin washer that can be move above or below the clip.

Raising the needle won't do much for cold starting anyways , it's got very little to do with idle. Changing the needle to a thinner one would have more effect but that isn't an option on these bikes.

Turn your idle back up , having it lower only makes it harder for the motor to stay running once it is started for what little gain it has to help it start.

Also make sure your o-rings and the outer seal/cover is good on your choke knob , if those are worn or bad they'll leak air past and not suck fuel as it should and make the choke less effective.


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Thanks for the tips ! I will set the idle speed back to normal then and check those o-rings and the outer seal ! The outer seal is quite worn from what I've seen when I'm pulling or pushing the choke.

From what I've been told so far I came to the conclusion that I have a lean condition at starting. I will order bigger pilot jets (not sure where to find them) and I will richen the mixture a little more.

So far it seems the right pilot jet and the choke is the correct fix for my situation and maybe a new battery ! (old one is 6 months old and has been taken care of but maybe its just giving up)

I think the choke can definitely act up since the bike felt rich after it starts and heats up. Where can I find the outer rubber casing of the choke and the o-rings to buy ?

Also I need to find the patience to take out the carbs take them inside the house and clean them really well ...

:clap:

I don't think you can get that choke cap on its own . The biggest would be if there is a lot of extra space around the shaft in the bore from it being worn out , will make it hard to seal up and have good control of fuel delivery . I have 2 different wideband meters that I put on bikes to be able to physically see what the a/f ratio is while running . Makes it much more easy to jet correctly and know what jetting corrections are needed.

For jets I've bought 1 or 2 of every size that was still available oem from Partzilla , but I no longer recommend bothering ordering from them , you'll either never see the order or it'll be backordered for 6 months , I gave up on them.

Jets R Us has Teikei jets FAQ Identify that jet

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The pilot jet has a small needle thingy that I have for blocking a passage I think. Not sure if the pictures are informative only on Jets R US.

I might considering buying a second hand carburettor that might be in better condition. I've seen dual carburettor kits from CR Keihin but they are really expensive ... and even after spending that chunk of money you have to tune them for your specific application.

Either way I have to make sure mine are really clean and all passage ways are clear !

Thanks for your help !

Bernek

Oeh yeah, a blocked choke passageway in the bowl is a classic. Most people dont clean that one. You really need everything to be clean and in good working condition, before you can finetune the carb. Otherwise youre just fixing the symptoms, not the problems. :D

As with the fuel/co-screw: You just dont give it a setting. You need to adjust if for the strongest idle (not necessarily the highest) each time you play with the carb settings. So theres no saying "set it to 2,5 turn out, and you'll be fine"

In general, it needs to be somewhere between 1,5-2,5 turns out, but you have some wiggleroom in each direction.

Under the jet pictures on Jets R Us you can click on the one below the dimensions and is blue , it'll take you to a separate page for ordering the different sizes they have available . The stock carbs do work pretty good , when tuned good,every passageway clean, and all seals doing their job .The ones on my hi-comp motor are working great, it's been dead reliable starter since I built it 3 years ago , just can't ride in any mist, drizzle or rain, heck even wet roads that create water mist from the tires and the left one freezes up the tiny air passage feeding the pilot jet and choke , she backfires and shuts down till thawed , unless I hold it at high rpms to run off the main jet . Stock motors don't run into that though .

The couple alternative carb option will improve performance and tune-ability ,however there is one huge drawback to them ,,, almost impossible to hook up the airbox ,unless you don't mind cobbling and crappy sealing intake runners or willing to run pod filters that really are only good for nice sunny dry days and preferably no offroading where junk from the rear tire can hammer them . For me no thanks .

There is however a new option that a guy from UK just made aware of and I have a set that I ran on my hybrid motor and that's the early '00's to '08? Kawasaki Ninja 250. Dual 32mm CVK's that slide right in the XT boots and fit pretty good. Once jetted right they are better than the stock ones and allow clean filtering . I will go that way with any XT I own rather than buying a set of replacement oem's . If you want to the 300Ninja EFI throttle bodies fit right in as well :innocent: But needs a Microsquirt injector controller and all the sensors added as well .




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The choke passageway is in the detachable bowl part ? I will try to clean and I don't want to miss this important one.

Thanks !

http://www.horizonsunlimited.com/hub...ammer_oben.jpg

Can I use a thin steel wire to try cleaning it ?

Hard starting could be valve also out of spec .. but I just changed them 1000 km ago when engine was rebuilt and I've checked them again 500 km ago so it can't be ...

P.S. can anyone confirm my picture above for the choke passageway ?

You can use whatever you want to get it cleaned out , the true size of the hole isn't important , just that it is open so the choke can suck up fuel , though I think that is how they control the amount of fuel the choke adds so if the hole is drilled bigger the choke will add more fuel when pulled.

As long as your checking the valve clearances correct and they're within sec they shouldn't be an issue.


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Yeb, thats the choke passageway.
I tossed my bowl in a ultrasonic cleaner, and sprayed brake cleaner through it afterwards. This was for my Dt125r, but simular setup.

Cleaned the carburettors. Changed the spark and charged the battery (now it works for 10 tries maybe more).

The mixture screw is 3 turns out now and it fires up almost each time but dies. After 2-3 attempts it picks up rpm and it's ok.

Engine seems to be running good but I still don't like something ...

If I stab the throttle (neutral) it bogs a little and died once (maybe it wasn't completely warmed up ...)

The weather is really cold now going bellow freezing most of the time. Should I try 4-5-6 turns out on the mixture screw ? The needles (both) are in middle position clip and the transition between carbs is running nicely.

I suspect the engine is not revving as high as it should (I have to test this - I've mounted a rpm/hours gauge and it recorded 4800 rpm and I did quite a strong acceleration) I think this engine should go towards 6000-6500 rpm will have to test ...

The signs is giving me it could still be leanish running since it takes 2-3 minutes to run on choke when started from cold and it has those start and die symptoms ...

Quite hard for me to tune it since I have to wait for it too cool down completly so I can try again ...

When its warm is really a pain in the ass to tune that mixture screw since I keep burning my fingers most of the time ... I've made a small tool to adjust it !

I don't know if I should try buy a second hand pair of carbs just to test it ... I can't figure out if the choke is busted or not ... but the tests that I've made tell me its working, for example if the mixture screw is 3 - 3.5 turns out and engine is warm and I pull the choke it almost dies from rich mixture ... is this normal ? I believed it could run on choke but at higher rpm ...

I don't know how much popping on the exhaust is normal on this bike. I can try go leaner and try to see if it starts better ...

Will have to test further and try to see if I can make it work. I just want it to start on 1st or 2nd attempt and keep running ... the engine fires up like I said but it dies and it doesn't pick up rpm ...

I've set my idle rpm higher like I've been told here ... now is at 1450-1500 rpm (when hot).

I just can't seem to figure out the dying at startup is from lean or rich but I don't think a rich running engine can die at startup it can only die if its lean or the compression is low or the spark is weak ... please advice here :)

Also the spark when I've looked at it it was yellowish not blue ...

Your lean on the pilot jet and possibly the left needle . I'd go up one size(for now) with the pilot jet and raise the needle 1 groove .



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What if I back out the pilot jet to 4-5 turns out ? The results won’t be the same as going a size bigger ? (I’m not trying to be cheap) but they are quite hard to find in Romania.

Please explain me why is the effect different ? The shape and construction of the jet itself?

I can go richer on primary needle no problem !

Please take in consideration that when I open the mixture screw the revs eventually drop since the mixture becomes too rich.

Please also explain me which part that I’ve said in my previous post made you say that I’m lean on the needle.

I’m trying to learn which symptoms are the best for lean/rich conditions on this particular bike !

Thanks a lot !

The screw will only adjust up and down about half a jet size (at most) its only for finetuning, you cant compensate for a wrong jetsize.

After 3-4 turns out, the passageway is fully clear, and you wont gain more by unscrewing it further.

Which viscosity oil do you run? Perhaps a heavy 20w50 (the first number beeing the important one in this case) will give the engine too much "drag" here at colder temps. This is not the main issue, but could be adding slightly to your problems.

Make sure you have the correct idlespeed, perhaps go up to 1400-1500rpm, and shut of the fuel-petcock a couple hundred meters before youre home. That way you start with fresh gas in the bowl, and have optimum conditions for a good start.

Having said that, I've seen the "problem" before, its not a big deal that you have to restart once or twice in cold weatger, but I can certantly understand why you want to get rid of it.

The oil that I use is Motul 7100 10W40 (do you think I should look for 5W or 0W ? not sure if its available for motorcycles... I'm afraid of the friction modifiers because I could easily find 0W40 from a car engine)

The oil has 1000 km and I consider that is in pretty good condition since its still pinkish color.

I will try just for the sake of it to set the idle screw at 3.5 - 4 turns out and try to start the bike again.

I've bought a digital rpm gauge that attaches to the sparkplug wire and I've set the idle to 1450 rpm. Will set it to around 1500 rpm (when hot ?) and test again.

I will look for a 50 idle jet since 48 is what I think I have installed (but have to check first).

My needle jet has a very thin pointy end is that for the fine tuning ? and the holes in the jet are calibrated for exact delivery ? something like 35 units from the holes in it and the rest of 13 by screwing it in or out ?

I ask this because if I remember correctly the tiny pointy end was a little bent last time I took it out (it actually fell out because I forgot to count the turns ...)

Thanks !

This is a photo that contains an idle jet that is 99% similar to mine:

https://s18.postimg.org/r8l9q3oah/pilotscrew.jpg

L.E. I just started the bike with the mixture screw at 4 turns out. It did start a little easier died 2 times and the 3rd time it managed to keep on running. Before it was 3-4-5 times it died then it started ...

This is a lean condition like I've been told and I have to find a bigger idle jet. At 4 turns out the idle is "stronger" (not higher) and I hardly need to use the clutch when moving the bike around at very slow speed.

Idle rpm dropped a bit and I had to set the idle higher to make it 1450-1500 rpm (maybe a half turn on the screw)

I will raise the needle (drop the clip) during daylight when I can take off the carburettors without freezing. Sadly I'm working outside and its quite cold.

As said that mixture screw is maybe equal to 1/2 jet size , you need a bigger pilot jet . The 48 should be fine , I can't remember what I have in all of mine but I know none are bigger than a 48 , more like 45 . You could have an airleak somewhere which is requiring a bit more fuel to make up for it . otherwise your fuel can just be that way and require a richer mixture. If you have a set of jet drills you can drill out the 48 about .001" and then file a slash across the number to remind you it has been drilled , I've done that a few times if it saves a bunch of messing around.

I generally have my idle set up around 1700-1800 , too low and these big singles get hard to keep running .


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I run 5w40 during winter, again, this is not the casue of your problems. I buy it from Louis.eu in Germany.

Ok cool thanks ! I will try to look for jets on LOUIS.eu or .de

Regarding the idle speed it's close to WR450 the setting that you use. I think it's 1700-1900 rpm for it.

Will try myself that and see how she starts :)

Thanks.

No jets on Louis for this carb, that was for the oil. KEDO - Performance Products have jets.

A #48 idle should be fine. Mine was #46 stock on my 2003 model

Theres cheap carb rebuildkits on ebay, something around 20-30$ for a complete kit, mine has worked flawlessly.

you dont mention checking the carb float level. surely you did this first before doing anything else?

I didn't adjust the float level. I think its only adjusted by eyeballing it few months ago.

I have the service manual for the bike and will check the float level and adjust accordingly.

It 8mm IIRC , you can put a clear fuel hose on the drain screw nipple and hold the other end up along side the carb going above the carb some. When you open the drain screw the fuel will fill the tube up to the level in the bowl . It should be 8mm(5/16" or .313") below the parting line of the bowl and carb body . So you won't have to take the carbs out of the bike to check.



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I started mine today after it sat in the cold for a while, it needed 2 restarts. No problem tho' :D

So I should just stop tormenting myself about 2-3 restarts ? And just live with it ? The bike is running great and during the autumn and summer was 1st start all the time.

I was riding 2 strokes in the past and being lean on 2 smoker is not fun at all.

My riding days are quite far apart recently ... I only start it once a week maybe once in two weeks and connect the charger to the battery to keep it in good condition.

I use the XT for mild off-road mostly and some long "walks" in the countryside.

Will definitely give this a try ! it's easy and like you've said I don't have to take the carbs off just for this.

Thank you !

Guys I have a question that might solve my issue.

Please take a look at the o-ring in this picture where does it actually go ? what is the correct placement for it ?

https://s17.postimg.org/5x667d9vz/pilot-screw.jpg

Thanks !

Does it go in the groove on the screw ? what is it's purpose to stop a gasoline leak ?

hi have a look at answer 4 hope this helps steve
http://www.horizonsunlimited.com/hub.../backfire-5560

Thanks ! I re-fitted a new o-ring in the correct place. The old one was broken in 2 pieces and worn out. Now the idle mixture screw is actually working and I could tune it (with warm engine) to have the best mixture. (it was betweem 2.5 and 3 turns out).

The starting problem is still there and I think the choke circuit might be clogged up a bit !

The rpm raise with choke but not too much maybe close to 2000 rpm and I've seen on the internet that some bikes when choke is pulled rev towards 2500-2800 rpm ... this could be one of my problems since the idling immediately after starting happened only when the weather got colder (0 degrees C and bellow)

Do you happen to know if it's possible to remove only the lower part from the carburettor without taking them off from the bike ? It's freezing outside and I work at -10 degrees C.

Would be nice if removing of the float bowl is possible without taking of the carbs.

Thanks !

:D

I took the carbs off again today and cleaned them really well and also cleaned the choke mechanism (found some black debris in there at the tip and around it).

The bike started perfectly at -10 degrees Celsius and idles without any problems.

I should have done this sooner but since I've cleaned the carbs two times in the past few months I couldn't believe anything could be clogged up. I use an inline fuel filter now and I swear I will never allow unfiltered gas to reach the carbs.

I used 2 cans of carb cleaner but I'm happy that it works so nicely now !

Idle is stronger and the mixture screw works spot on ! Also the choke was loose before and now it takes a little bit of force to pull/push it (not sure why).

Thread can be closed ! Problem was solved and I'm a little bit ashamed that I failed so many times to find such an easy fix.

I would like to thank all of you who posted and tried to help me out !

Bernek

Happy riding! :D:scooter:

I figured out something interesting today !

I cleaned the carbs again and they are pristine now. The float level is 27mm and the book says 25-27mm. It start better recently but not the perfect way.

So do you think those 2 mm are that important ? (bowl fuel level).

I also made another discovery ... I took of the seat off and covered the air intake scoop with my hand while starting to create a bigger vacuum than normal to check for a lean condition.

It's still running lean !! (at least at startup). The bike started and revved up immediately at -15 C degrees Celsius (it was standing there for 2 weeks no start during that time).

So I'm really lean but the question is:

Is the choke mechanism at fault ? or the pilot jet is way too small ? (I'm using the original jet.)

I have a full carburettor repair kit in mail waiting for it to arrive. With higher idle jet and all the rest.

But I don't know how to test the choke mechanism ... it clearly makes a difference with it pulled out or pushed in. In the past (2-3 months ago) I remember if I was pulling it out the bike would start to hiccup and almost die when fully warmed up.

I also made another discovery that improved the starting immediately. I flooded the carbs due to the fact that the float valve wasn't closing and it was dripping from the overfill hose. The bike started perfectly again (even with fuel flowing from the overfill ... so again I'm too lean and this points me to fuel level in bowl).

A little too many equations for me recently :D

Can someone with better knowledge and experience help ?

THANKS !

How does the 48 jet size translate into measurement units ? is it 0.48 mm ?

Wait till you get the repair kit. Its not easy to know whats going on if the float valve isnt sealing.

A #48 jet should be 0.48mm, so if its not enough, you can drill it to 0.5mm afterwards.

We just had -8c and my bike struggled a bit aswell, since it hadnt been started in a few weeks. For me, luckily all thats needed is fresh battery, as its 5 years old.

The engine doesn need much air at idle, so blocking the snorkel partially, or even fully removing it, wont make much, if any difference in tickover.

The jet number isn't always the hole size , they often go by flow rate , but not all are rated the same , I don't know offhand which ones went more to the hole size but either way I think it comes out close , it's always best to stay with 1 brand when changing jets .http://www.historicmotorcycle.org.au...carby/jets.txt

http://www.jetsrus.com/FAQs/FAQ_miku...ihin_sizes.htm



Putting you hand over the air intake side of a carb is an old trick to force fuel up into the motor. The motor is creating vacuum and if it can't come through the carb bore it tries to come through any hole it can thus really pulls the fuel in , doesn't indicate a sign it's running lean though .

I just obstructed the air intake a little bit. Less air more fuel ? why isn't that a sign for a lean mixture ? Please explain me ! I didn't block it completely just allowed less air to enter and it started like it should have and it ticked over really nicely. After 5 seconds I could remove my hand and it was idling nicely on choke...

I'm a bit lost now... I'm not going to drill the jets yet and the valve and seat for the bowl is closing perfectly (it has been changed 2-3 months ago by me brand new) but from time to time when I remove the carbs they leak until I kick it into place with the wood part of a hammer just smack the carb 2-3 times (easily) and it starts working.

Aren't all these sign showing me the lean condition at starting at least ?

Valve and seat are new ! I changed them few months back. Read my previos post please.

At least for me it makes a huge difference in starting. Without blocking the air intake partially it turns over more times and it starts and dies after 1-2 seconds. If I block it partially it starts faster and idles (doesn't die) nicely. I can remove the hand after a few seconds and it runs good on the choke !

I have, but I also read where you just talked about overflowing carbs, thats why i recommended to change the valve and seat.

After that you explained that it was only after installation (but still sounds like a regular thing for you) Its pretty hard to guess theese things.

Let us know how the #48 idle jet works out for you. That woudl be the next step. As for the choke, just make sure the passageways are clear, and the rubberbits on the choke-plunger itself is in good nick :D

I can't wait to test with the #48 myself ! About the choke I will try my best. Have to look for a sectional photo somewhere so I know which passageways it has and how it works. This is very important to starting and I can't say that I'm 100% sure that it works as it should :(

I guess with the idle jet swap I will work harder on the choke and see the results.

Thanks again !

When you take the bowl off there is a brass tube that sticks down into a hole in the bowl itself , there should be an o-ring around it. There is a small hole at the bottom of the bowl next to that tube hole that must be open so fuel from the bowl can fill it. That tube is what feeds the choke . It is common for that little hole to get plugged if fuel has dried out at some point and is really hard to get open again .

None of these motor should need bigger than a #48 pilot and that's even a bit big from all the XT's I've had but it may be possible . There is a couple small feeder passages on these carbs that if partial blocked will cause hard starting cold , they're kind of a fussy design.


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The small opening in the bowl for the choke tube is clear also the tube because I've sprayed carb cleaner (a lot) inside both parts and they are 100% open. I will have to check for the o-ring next time I open them up ! Not sure if it's there but I will put one if it's missing.

I haven't bought this bike new ... I just invested a lot of time and money in it to make it as best as I can (afford).

The #48 jet will arrive this week maybe the next and I will definitely check what you mentioned when I change the jet.

Thanks a lot for trying to help me guys ! The help I can get here (my small town) is very limited and most mechanics work from self learned experience (which is most of the time not accurate and appropriate).

The kit arrived ! Do you guys recommend that I change everything or just use the 48# pilot and adjust the fuel level a bit from 27mm to 25mm.

This is my main plan just to change the idle jet and a minor fuel level adjustment. I will also trow in a new spark ... (its been maybe 200 km with the old one). I just want to make sure all the start conditions are optimal and it should start very easily I hope.

The battery is on trickle charger and performs at its peak.

I’ve changed the pilot jet to #48 and the starting is great !

I looked at the hole diameter of the existing one (old one) compared to the #48 new one and the diameter of the hole was much bigger ... hence the old pilot jet (unknown size) was clogged up ... I can’t believe I couldn’t clean it ... I’ve stuck a needle and boiled it and used some compressed air after and eventually it cleared up ...

So the fix was so simple but I guess I have to learn from my own mistakes.

The bike is really running as it should !bier

Awesome, great news.

Yes indeed ! It started first attempt yesterday and today no problems at all (engine cold or warm). Really happy now !

I even managed to dial in a mixture screw perfectly and it idles and starts really nicely.

It's an old bike but still gives me the thrills and makes me grin when I accelerate on a forest road !

Don't think I will ever change it :) just hope to find parts in the distant future.

I already started to buy second hand parts (in good condition) to have it when I will be needing them. Sometimes you can find them cheap and I just can't help myself buying a few.