89 XT 600 ,, popping through the carb and running lean problems
 

Hi , I need some help Please . I bought an 89 XT 600 with the top end off and needing to be rebuilt.

I just put new Yamaha .50 piston and rings in it and new timing chain , new valve seals, also lapped the valves into the seats. put it on the bench put diesel and it did not leak though the valve seats . we put the engine together ,, cam lobes all pointing down , piston up top dead center and the marks on the cam sprocket and fly wheel lined up. adjusted the valves to maximum clearence specs . I also cleaned the carbs , put a 130 main jet in and turn out the mixtures screw to 3 full turns . I even put on brand new intake manifolds/boots on it and siliconed the rear air box boots around the seal where it meets the airbox. I used propane to see if there is a leak somewhere , never made a difference in the way it ran.

it kick starts fairly easy , seems to idle but it with pop back through the carb , the plug is white when I pull it out to check it. the engine heats up really fast .

we couldn't do a air leak down test or compression test because my buddys fitting didn't fit where the plug went , his fitting was to big . but starts easy and the deisel didn't leak through the vavles while on the bench . he did have a fitting to just put air in the cylinder though , he put 45 lbs going by the commpressor guage and we did get some air through both intake valves and 1 exhaust valve .

Can someone point me in the right direction , am I having carb problems or head problems ,, I'd hate to pull that head back off , but if it has too , then it has too.

Thanks Randy

Did you forget to fill the oil?!?!?! doh

First things first!

Make sure the oil is circulating nicely!
just turn the bike on and immediately go to the oil blew screw on the top of the oil filter casing and remove it very carefully because if the oil is circulating as it should you will get an oil shower!

(it happened to me a couple of weeks back lol)


Vando :cool4:

Adjusted valves again. Have a look at timing chain

I took off the valve adjustment caps on the rocker cover ,, there was plenty of oil up there ,So I'm assuming the oil is circulating, the valve clearence is still where I adjusted them too.

Think maybe the timing chain is off a tooth ?

carb
 

I'd first check the carburettor. Why did you install a 130 main jet? The orginal one incorrect? How do know? According my info most LH side mainjets are 135 or larger on the XT.

Check:
- Float level
- Synchronisation of second stage - should not open at the same moment as the first stage, but only after 5 - 6 mm lift of slide valve first stage
- Needle positions first and second stages
- Remove the little filter on top of the float valve seat
- If this is an older bike, the mixture (idle) screw might need another turn out - but wait till you have the rest sorted

I don't think you have a head problem.

Auke

2003 model xt600 has 130 primary mainjet (left carb), and 120 secondary jet. ( right carb) And they are jetted fat from factory.

I have another set of carbs off an 86 xt 600 parts bike that I picked up . I put them on it ,,,,it ran the same as with the original 89 ones,

Both sets of carbs had 125 primary main jet in them main carb , thats why I went up to a 130 , I do have a 135 I could install .

I took the little filter screen out already , the other set of carbs didn't have one.

The needles are fixed in the secondary carb , so I didn't mess with the needle in the primary one.

I didnt touch either set of carbs butterfly adjustment for the secondary carb,, since both set of carbs made the bike run the same way , thats why I was wondering if it has a head issue.

I'm puzzled.. air mixture screw is 3 turns out already .

Thanks for the feedback and guidence , I really need the help .. I'd hate to send it to the dealer to get straightend out , it'd cost me a fortune .

Thanks Randy

Take your air filter out and make sure all passages are clean and try again. The air box has a tuning effect much like the exhaust has and any blockages / dirty air filters or corroded gauze can have this sort of impact. Especially around the midrange upwards.

Today , I turned the mixture screw out another turn , so now it's 4 full turns out , still doing the same thing.

I cleaned the air filter and air box before I did the carbs , now I have a single small air filter , it goes over the metal cage,, but I believe theres supposed to be another one that goes over the smaller one and cage , making it a 2 stage filter set up.

I looked it up online for oem parts and it shows 2 filters ,, Man would that be nice if it's only running the way it because of the filter set up ..

It does it also though with the choke full on .

Thanks

My money is still on air starvation. The carb wont work right if there is an intake imbalance. You may want to check that the silicon you put on the back rubbers hasn't blocked any of the small air entry ports at the back of the carbs. For future reference, use grease and not silicon.

back to settings ...
 

As I understand we are talking here about a problem with idle running. This means that the airfilter (in / out / 1 or 2) is irrelevant: the flow is so low that there will be hardly any resistance with whatever setup.

So, if it's the carb, we have to look at mixture preparation for the idle circuit.
Lean running:
- Low float level, you did not say you checked that
- Low fuel flow, although a long shot: same as for air filter
- Air leaks
- Synchronisation. I have seen these carbs 'adjusted' so that the 2nd carb is slightly open @ idle - there will not be enough air flow to make petrol flow from 2nd stage jet, but there will be additional air into cilinder, leaning out the mix
- Blocked idle jet or passages
- Air leak in the coaster system?
- The needle in the first stage does have a slight influence on idle running - check again the setting. (Remark: needle second stage fixed? Not on European bikes, and I cannot think of a reason why they do that on USA bikes)
- Why not turn the idle mixture screw out another few turns - just see what happens. Improvement -> we are too lean. Worse -> we are too rich

I would vote for lean running, but in the same way the carb should be checked at idle for too rich running.

The best way to troubleshoot a carb is by bringing it back factory settings, and then to start changing - one thing at the time.

The silicone is only on the boot section That meets the air box ,, I have only the tightening clamps on where the boots go over the carbs .

I also ran the bike with no silicone on the boots back there and it was doing the same giving me a lean condition , thats why I put the silicone back there to eliminate that area from an air leak , I had already replaced the intake manifolds before this also.


I'm willing to try anything though. I hate trouble shooting.

Thanks Randy

I'm going to have to take the carbs off , I never did check the float level . How do I adjust that to make it richer ? I know there is plenty fuel flowing into the carb .

I'll have to check for the sync adjustment too . set it at 5mm .

I took a propane torch ( not lit of course ) and let it flow all over the carb ,, if there was an air leak at the carb it would have sucked in the propane and made it run different. it didn't at all , So I think I can eliminate an air leak .

Here in the U.S. all the mfgs, have thier bikes running lean right from the factory , due to the federal EPA standards for emmisions.. that might be why theres no adjustment on the secondary needle , I didn't even look at the primary needle adjustment since I seen the secondary.

I do have the spare set of carbs off the 86 parts bike , that I did try on this bike and it ran the same . I could take that apart and Inspect and reclean it , adjust the sync on it , try to start fresh with that one.

Thanks Randy

float and needles
 

Well, let's not assume the lean condition. What I meant is to adjust the float to the factory setting.
From the net I found the following settings for the carb (European 43F):
Teikei Y27PV/43F00
main jets: L/R 130/125
Needle Left: 5C37 / 4th notch from top (=blunt end. Are there really no notches on the needles? see picture here: [url=http://www.xt600.de/xt_werkstatt/_special/-special-vergaser/sek_duesennadel_assy.htm]www.xt600.de Sekund

another try
 

Can't get this working :frown:.
Continuation:
Right needle: 4A71 / 4th notch from top
Idle jet: 46
Float height: 25 - 27 mm. Adjust: float bowl off, carb upside down, measure distance between bowl mating face and top of float. Adjust by bending copper tap on float needle. 25 mm = richer, 27 = leaner. Keep it in that range for now.
idle speed: 1300 +- 50 rpm
Mixture screw: 2,5 out basis, although experience learns that older bikes need more turns: 4, 5 ,6 is not uncommon
Synchronisation: 5 mm, although there was a later bulletin from Yamaha, requiring 6 mm

Possible issue: it might be that there should be washers between needles and slides. Is everything there as it should?

Possible issue: loose electrical contact in the ignition, that plays up with vibration. All connections clean and tight?

Good luck

Thanks Auke ,,

I have my work cut out for me. I'll have to tackle it over the weekend. I was also wondering about the electrical conections, I'll go through them also.

Thanks Randy

Hey Vando ,

My Grand Parents on my Fathers side are from Portugal ,, my grand mother is from Fial and my grand father from St. Micheal .

My grand mother from my mothers side is from there also ,, don't know where though , I think Maderia , not positive though .. My mothers father ,,,,,, well he was a frenchman . :oops2: ..

So I'm 3/4 Portuguese :thumbup1:

Randy

Hey Randy!

really?
That's cool!
São Miguel and Faial are really good islands to travel backpacking!

Have you ever been around here?

Oh, and most of my family on my mother's side is all living in Hudson MA(close to Boston, Fitchburg, Worcester)
Where you from in MA?

It's been two years in January since I was last there :\ been there maybe 12-14 times already.. I absolutely love it there!


I was going for a trip to all the Azores islands with a girlfriend this summer in my XT600E but the bike wasn't finished yet and she had to leave very early..
We did manage to go backpacking to São Miguel for a few days..

Vando :thumbup1:

Vando ,,, Wow it is a Small World ,,

I live in New Bedford , MA. I live at the begining of Cape Cod . My city is Known for its huge seafood industry . It used to be a big Whaling City back in the day. I'm 1 3/4 hours from Fitchburg. My brother lives in Lunenburg , MA. He's a town over from Fitchburg.


I've never made it to the homeland of my family .. I'd love to go to Azores/Portugal .
I don't know where to go there and 1st I need to learn to speak it alot better. I've heard it's beautiful there.

Randy

I actually have a good friend who moved from worcester to cape cop..
She even invited me to go over there next time I'm in the US and I said: sure, if you introduce me to your girlfriends! lol which will hopefully be next summer!

yeah, it's about 1 1/2h drive on the 495 south from hudson to the capes..

Well, you should visit everything here! all the islands! All of them have awesome places! well, except Corvo.. it's got a main street going up and down the island lol about 300 - 350 people live there..

And if you love backpacking and camping as much as I do you will love every single moment you're here!

Portuguese is pretty much the same as spanish...tho most people here do speak english!


Vando :thumbup1:

Did you check to see if the carb mounting rubbers were still fully attached to the aluminum parts? Leakage will affect your mixture. Mine looked OK but werent. I used gorilla glue to put them together and all has been well for several years now. I had problems getting through emissions and rough running.

Good Luck! Steve

Thanks Steve ,, I bought brand new ones already and they're on there .

Randy

Thanks Vando, I'll have to have a sit down with the wife and see if we can fit it in our budget to vactaion there... Next time your heading this way give me a heads up we can get together. I currently have a couple of ATVS we can go riding on , also if the XT is straightened out and on the road , you can take that and I'll take my Harley and I'll take you on a tour of the Newport , R.I. mansions and water front .. breath taking (both scenery and the women :whistling: in the summer time around there), bring a camera.

Randy

do you have a cdi from the parts bike? If so swap it out. they are known to go bad.

I took some discs out from the super trapp , I'm down to 4 discs Wow what a difference .. it smoothed right out no more popping in to the carb. Still a little lean though .

So I already have a new 135 main jet , i'm going to put in it. theres a 130 in it now . stock was a 125. the pilot jet is 46 , I think I'm going to go up to the next size on that also .

It's deffinalty a carb / air flow issue . it'll now idle no problem . but while riding you let off the throttle , the RPMS hang up there for a little bit before dropping , which tells me it's still a little lean.

I'm getting closer to dialing it in.

Randy

Hanging rpms has nothing to do with the mainjet, thats for wide open throttle.

Go one up in idlejet, or try to adjust the CO screw out a bit further.

usually, the hanging rpms means an air leak somewhere in the air system...

Are you sure you're that you've fitted the carbs right in the carb boots and it's not the clamps holding it in place?!?!

So, what was the final word on the fix? (I assume you must have started riding again and forgot to post your solution, lol) :mchappy:

I have a very similar problem, its running super lean and popping on decel and dying sometimes when it pops usually when shifting down. I had to get a new air filter (UNI) and the previous owner in his infinite wisdom gutted the muffler. So obviously I'm getting a ton of air in and no back-pressure out. It currently has a 130 main jet and kicks over fine but runs lean. The air mix screw is out 4 -5 turns and it dies if i put it in under 2. How'd that 135 work?

I went through the checklist mentioned earlier in the mix and no leaks in the boots or intake tubes. I started stock with everything and it would barely run. Anyone ever make their own baffle setup to replace a rusted/damaged stock one? I dont have a supper trap and so it isnt as easy as just removing a few baffles. :( I do have a welder though! :clap:

I recently was having issues with my 1984 XT600 (LC) dying at highway speeds. If I let off the throttle and tried to cruise at 55mph it would sputter and die. After a weekend of troubleshooting I found out my XT600 had a black screw in valve under the tank. OK, so California models suck. Literally, the clogged "roll over valve" was causing a hardcore vacuum in the tank and making gas and air evacuate the carb bowl and travel backwards up the fuel line. This "roll over valve" is listed as #26 on this diagram:
1984 Yamaha XT600 (CA) XT600LC Parts, 1984 Yamaha XT600 (CA) XT600LC OEM Parts - BikeBandit.com

The previous owner just removed the canister and plugged a long piece of fuel line from the broken roll over valve to a nipple on the carb just above the fuel line nipple. http://d26ya5yqg8yyvs.cloudfront.net/eek7.gif I just removed the roll over valve and it will just act like a vented tank now I'll eventually try to put a one way valve on there like they sell for MX bikes to let air in but no gas fumes out. in the winter when I store it I will WD40 the empty tank or fill it with gas and add stabil to prevent rust from condensation.

The scoot will run with that nipple on the carb plugged or unplugged. It just makes a sucking noise like "ffuff fuff ffuff" as you go down the road. This leads me to believe that dirt could get sucked into my carb bowl... so I'm going to cap it off. pretty sure thats a safe bet as the parts fiche doesn't even show the nipple on the carb.

So if you have stumbling issues at highway speeds make sure its not due to crappy California emissions gear that is faulty/improperly removed. I made sure this fix was repeatable and sound advice. I put the parts back on and the fuel line to connect them and it caused stumbling EVERY TIME. Take it off and it stopped acting up EVERY TIME. Also make sure you're not lean due to your airbox snorkel coming off under your seat as I'm sure that was not helping the troubleshooting process. doh

Just thought I'd share since I was sooooooo pissed off at it this weekend and there wasn't a ton of California Emissions stuff linked to sputtering out at speeds. And I know the roll over valve was bad because air could not be sucked or blown through it and if tapped on a hard surface debris would come out of it.