Still Smoking!
 

Gday Guys.
As you may remember, a few weeks ago I replaced one of the valve stem seals on my XT600 as it had been blowing smoke on startup. As a few of you predicted, this didn't fix the problem....
I'm now about to strip the bike down, with the aid of a factory service manual that i have, but i have one question:
Obviously when i go to replace the cam and hook up the cam chain i will need to see the mark on the crankshaft cam sprocket to make sure that it lines up with the pointer on the crankcase. All of the diagrams in the manual show this with the left hand side cover and the magneto removed. I want to try and avoid removing this cover and the magneto if i can help it, so is there a way that i can see when these marks line up without disassembling the whole left hand side of the motor? Are the marks viewable if you look down the cam chain hole in the left hand side of the head and barrel? Obviously i don't want to get this wrong....
Thanks in advance for your answers.
Sometimes the bike starts as clean as a whistle, other times it blows enough smoke to completely smoke out my driveway. It's very tempremental.
Hopefully we find something seriously wrong once we remove the head. One fella that i know through work once had a KLX650 that blew smoke like my bike is doing after having a full rebuild. After stripping the motor for a second time he found that one of the valve guides had a hairline crack in it. Perhaps this is what has happened to my XT??? I guess i will find out when it's in pieces!
Cheers, Dan.

Hi Dan, if your not removing the flywheel from the crank you won,t need to see the mark. just align the timing marks on the flywheel with the crankcase mark & slot the cam sprocket in with its marks lined up, then bolt it unto the cam. turn the engine over by hand a couple of times just to make sure though! i,ll be interested to know what you find as mine has the same problem! Cheers T

Thanks T.
Yesterday we removed the head, after discovering that there is actually a mark on the flywheel to tell us when the piston is at TDC.
The intake valve that i have been concerned about is now even wetter with oil than it was last time. This valve seems to have be slightly damaged on the end somehow, where the collets hold it together next to the valve springs. It was very tight and difficult to remove through the valve guide.
After inspection of the head and comparison between all 4 valves, it appears that the 'problem' valve hasn't been rotating as it should during operation. Perhaps this has caused it to wear in a funny way, or overheat and cause damage???
We can see marks on the head, underneath the other 3 'lower valve spring washers' which indicates that they are working correctly and rotating as they open and shut.
I will be ordering new parts through yamaha tomorrow and replacing that valve and it's valve guide.
We've got a feeling that oil is somehow getting down between the valve guide and the head when the engine is hot. This means that when I shut off the engine, all of the oil is dripping down onto the intake valve, and getting burnt the next time I start the bike.
Fingers crossed we're right and replacing the valve and valve guide fixes this problem.
I'll keep you posted as to what happens.
Cheers, Dan.

Well, I picked up the parts that i need from Yamaha this morning, including a new intake valve and a valve guide.
The head is now off having the guide replaced, so it will be interesting to see if they find anything obviously wrong as they remove the guide.
Should have it back by the end of the week, ready to put the bike back together on saturday. Will let you all know what happens and If it fixes the problem.
Cheers, Dan.

I got the exact same problem. about 7 out of 10 starts it will blow smoke on cold start up. Only sometimes it smokes when i start it in the afternoon to go home from work (ie 8 hrs since last ride) but any shorter intervalls and it never smokes. Also i have noticed the colder the atmosphere in the morning the more likely it is to smoke.
I have never done anything about fixing it beacuase it is only 10seconds at start up and the engine has had 71000km virtually trouble free, So i don't want to pull the top off too soon (i dont awnt to have to replace everything in their just yet)

I'm eager to see how you go

Well guys, whilst my head was off at the Engineering shop they found a couple of things wrong with the troublesome inlet valveguide. It turns out that from the factory, yamaha have put the retainer clip on from the bottom of the guide, which left two distinct score marks along it. Then when it was pressed into the head, this obviously left score marks in the head.... This could quite possibly have been how the oil was making it down into the inlet port.
The other thing is that this particular valve guide was drilled off-centre. that's right, the hole wasn't in the dead centre of the valve guide...
Anyway, they had to bore out the valve guide hole to get rid of the score marks that Yamaha put there when they assebbled the thing, and then make up an oversized bronze valve guide.
After getting the head back we put it all back together and she started first time i hit the starter button. As the exhaust had quite a bit of oil in it from before the repairs, we expected it to blow a little bit of smoke upon startup, which it did.
It's done nearly 100kms now (over 4 separate days of riding) and it is still blowing smoke un startup. :(
My gut feeling tells me that i haven't solved this problem yet...
The bore looked perfect and a compression test came back at just over 140psi, so i doubt very much that the rings are the problem.
This has almost got me stumped...
Does anyone have any suggestions?
I have a bike that isn't even 4 years old, hasn't hit 15000kms yet and is giving me so much grief. There must be a problem somewhere, as it never blew smoke like that when I bought it new and rode it off the showroom floor....

Look at the bottom end!
 

If all oil from the tank drains to the engine through a slightly worn oil pump and / or check valve, you will have a lot of oil splasehd against the cilinder wall at startup. The piston rings will not cope sufficiently to avoid the smoking. After some time, when the oil circuit is balanced out, the oil level in the engine has dropped and the crankshaft does not splash oil around anymore and the smoking stops.
I did this suggestion already (another thread?) - worth checking after an oil change when you are certain there is no oil in the engine.

Auke

Yes, I do remember you suggesting this Auke.
In the past I have checked the top tank after the bike has been sitting overnight and it was still full. So I assumed that it is not 'wet sumping'.
I will definately check it again though.
One other thing that i will try is disconnecting the crankcase breather from the airbox, to see if that makes any difference. The engine doesn't appear to be leaving any liquid oil in the airbox from blow-by, but It will rule out another thing that could be wrong. Obviously I will block off the hole in the airbox to make sure no un-filtered air gets in.
Cheers, Dan.

Hi Dan, i know how ya feel mate! have stripped mine three times now to try and cure this problem! not gonna give up though, she,ll be goin on the operating table next week!! i,ll keep you informed when something is found. cheers T

good advice
 

My engine is showing the same fault, i know it is not top end,recent unrelated work[broke head stud]had very careful inspection of guides ,valves,bore and rings little or no wear--so thanks for that auke
good advice--check valve--where is it? Bike is a mongrel makes ordering parts a little difficult 1vj chassis 2kf bottom end 3aj top end italion import
i think it was built for a purpose--

Checkvalve location
 

The checkvalve is inserted in the clutch (R/H) cover. If you remove this cover you will see a kind of seal at the bottom, there's a steel ball and a spring behind it.
Suggest also to check the oil pump, for that you need to remove the clutch and the pump itself.

BTW: as far as I know, the checkvalve is the same for all XT6 models.

Auke

Thanks again will

keep yous informed franz

I got around to fitting a new clutch cover gasket,the oil tank is full--not wet sumping--but still smoking on startup,not as bad as before gasket--not nearly..goes really well always does , still a great bike.

Mine is still smoking... Haven't solved it yet, but as Mini_S_Man has experienced, its getting warmer where I live now and i've noticed that the smoking isn't as bad....
I'm gonna take the bike off the road and then around christmas time when i've got the money i will strip it down again, to have a good look at the piston and barrel.

just been reeding the postings here and something caught my eye.
Its been stated that the valve was tough to remove from the head.

Be aware that when doing this you should gently remove the burrs caused by the collets. if you dont forcing the valve through the guide will damage the guide and then you have a whole lot more money to spend getting the head fixed with new guides.

not sure if this was done in this case but most manualls i have seen have recommended this to avoid damaging the guides.
similarly when removing shafts from oil seals(final drive, gear change) tape up the ends where splines or grooves are to avoid damage to seals as they are pulled through.

is the engine breather pipe causing oil to collect in the air box during your ride and then when its been stood and you start it again this flushes into the engine causing the smoke??
if the choke is making it very rich to ease starting maybe its washing some oil from the bore on startup. from what you say i presume it doesnt use loads of oil??

Gday Smokinrider.
Yes one of the inlet valves was tough to get out of the valve guide, but we planned to replace the valve and valve guide anyway, so we just pulled it through. Even after we ran a file and then some wet and dry paper around the end of the valve stem to remove any burrs, the old valve still wouldn't fit in any of the valve guides. Still not sure what was happening there?
There is absolutely nothing going into the airbox via the crankcase breather. The airbox has always been clean and I've currently got the breather disconnected from the airbox which has made absolutely no difference.
I have tried turning the choke off instantly after the bike starts, but I will try that little trick again tomorrow.
I have even run the carbs dry by turning off the fuel tap and letting the engine run until it stops, to check that fuel isn't leaking down through the carb and washing down the bore. This made no difference either.
Thanks for the suggestions. Keep them coming!
Cheers, Dan.

Potentially sounds like a sticking valve to me. Pehaps bent or worn.

Does the bike only smoke when its been left overnight etc. Does it smoke all the time ??

You say it drinks "a bit". How much is a bit ??

If an engine smokes for a few seconds on start up its usually always a leaky valve guide seal. If its smoking all the time then its potentially worn piston rings too.

Have you reassembled and retried yet mate ??

Gday Ted.
I'm assuming that your questions are for me and not the other fellas in this thread that are having the same problems.....
My bike seems to blow smoke any time after it has been left long enough to cool down.
I've started it about 90 minutes after riding it to work and it blew smoke, but then i've started it about 4 hours after riding it to work on another day and it started without blowing a thing... It's pretty unpredictable.
It doesn't really appear to be using any oil, but when this problem first arose and i took the bike to yamaha for a service, they thought that the oil was very dis-coloured (it had been in the bike for around 1500kms and not even 6 months).
All the valve stem seals have been replaced with new, genuine yamaha ones and everything in the head seems to be in good order now. No valves are sticking and/or bent.
Even though the symptoms point towards the valve stem seal / valve guide region, i'm thinking that i will have to strip it down and replace the piston / rings, just to rule them out as the problem.
Dan.

Dan,
10 out of 10 for perseverance.
I am not too surprised the original valve guide was not bored central, it is machined after the guide is fitted in the head and the bore should line up with the valve seat.
It would appear to me that oil is some how getting into the chamber, it may be getting in while it is running but in such small amounts you don't see it.
Could it be a porous head casting some where on the inlet side.

Don’t let it beat you

Steve

Whats the mileage on the bike ?? have you done a compression check ?

these faults all sound a bit of a pain. i would say from my experiences of this sort of problem that if its only smoking for a few seconds on start up and the oil level doesnt drop then it isnt really worth pulling the engine apart several times to fix. it may be the oil control ring as suggested previously and if this is the only ring worn it wont make a blind bit of difference to the compression. make sure when you reassemble the pistion the rings all join at different places on the piston. eg top ring at 1 oclock 2nd at 7oclock top oil ring at 11oclock and botton oil at 4 oclock.

my dr uses about 250mm per 150mile ride. no leaks and no smoke?? i put it down to too thick oil staying on the bore and being burnt so efficiently it doesnt produse smoke.

Unless its a 2-smoke, there shouldnt be any oil on the bore when the piston stops. Maybe a film but not enough for visible smoking. If your getting oil slipping past the rings then it "should" show up on a compression test but i dont think i would bother pulling it apart for that unless compression is down and you want to keep the bike.

Dans smoking but not ALL the time theres a clue in there somewhere..mines a good thick cloud of white smoke till it warms up then its fine..certainly its not a usual oil burning issue..somethings not right..i will have another poke about..ty

i think yours in prob a bad valve seal or head gasket !!

The bike is a 2002 model (I bought it brand new myself) and it's now done just over 15000kms. Not much!
Yamaha did a compression test for me (at my request) when i last took it there for a service. It came back at 140psi, so according to the manual, its still within tolerance.

As Smokinrider has said, it could possibly be a dodgy oil control ring (but this wouldn't necessarily cause the oil in the inlet port).

As SteveAttwood has said, the head casting may be a pouruos somewhere around the inlet port? Probably not, as it never blew smoke from new, but a crack is always possible.... We had a look for any cracks when we removed the head, but we couldn't see anything that we were suspicious of. Next time the head comes off, i'm going to send it off to be inspected anyway, just to make sure.

Thanks again guys, Dan.

There aint many places you can get oil leaking in really... valve seals, rings or maybe a bad head gasket.

Maybe a cylinder leakage test is next !!

Good luck either way.

XT600E Smokes on cold start
 

To add my experience on the cold start smoking issue... My 02, 22500km XT600E smokes probably 5 out of 10 times on startup - almost certainly due to overfilling with oil and it getting back into the air filter/breather circuit. The bike is used 70% off road and due to it's hard life gets oil changes about every 1700km / 3 months. I'm scrupulous about putting in the amount Yamaha recommend (about 2.8 litres), but the breather pipe is always oozing a little oil and the airbox is pretty oily - it doesn't use any oil in between changes. It's never blown any seals etc, so I'd rather err on the side of caution and have it oily - it's better than too little!
A be a bit of an idiosyncracy with this particular engine perhaps?

hey dan.. Jumped back from the second thread on this.

Im still very jubious about your valve seals, maybe the shop didnt do a good job and maybe their "custom" valve guide isnt upto the job.

you compression seems fine if its in the 140's. You say it only leaks when its been sitting !!

I think oils working its way past the valve guide ever so slowly and smoking on start up.

i think its unpredictable as you valves are always in random positions when you stop the engine..

I think the shops maybe made a bad job of your valve.

A cylinder leakage test is required here...

also..... You can remove the head, lay it on a non-absorbant surface, clean it and drop WD40 down the ports and leave it 8 hours. See if any works its way through the valve guides and seals.

Hmm, well the workshop made the guide and pressed it in for me. They are a very reputable shop and i'm certain that they have done it properly.
We re-assembled the rest of the head, valves, valve guide seals etc. We then turned the head upside down and dropped the valves into place (without fitting the valve springs) and then filled the combustion chamber with white spirits to check if there were any leaks around the valve seats. We kept using this method and lapped the valves in as necessary, until they no longer leaked. I don't think there is anything wrong with the head.
I still suspect the rings and bore though, as my oil it turning dis-coloured very quickly. There's no way that this can happen due to faulty valve guides and/or valve guide seals....
Dan.

1) how quicky does the oil discolour ?? What colour is it turning. If you mean it goes from clear - black, then thats perfectly normal.

If its throthy or white then there is a problem with contamination.

The bike air cooled so no worries with contamination there. Possibly a gasket somewhere.

If the oil smells like petrol then yes, the air/fuel misture could be getting forced through the rings into the oil bath below.

Odd with high compression though. You sure the carbs arnt overflowing into the bore ?

After only 150 miles or so the oil is filthy black. It shouldn't turn dirty that quickly...
Definately no fuel leaking through the carbs and into the bore though.

Completely ignore what colour it is. Its normal to change colour that quick REALLY !!

Smelling oil is the way. Should smell good. Not like coal or petrol.

Ok, Thanks Ted.
Will give it the 'smell test' after i get it back on the road and change it back to mineral oil.
Cheers, Dan.

Mineral oil wont do anything now (if ever. Its questionable about it helping to bed in rings)

What oil are you using and what kind of temperatures do you live in ??

ed

I've been using Shell SX4 15W 50, which is a semi-synthetic oil.
This problem reared its head about April last year where temperatures down here in South Aus were probably around the mid 20's. Temperatures then dropped down to as low as 5 deg for winter and then by the time i put the bike away and let the rego expire, the temperatures were back up around 30 degrees.
Dan