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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