can the cam chain slack produce failures?
 

Hi, experts guys out there, I have a XT 600 and I rebuilt the upper engine, meaning cylinder, piston, rings, valves seals, seats etc. because of gray smoke. I noticed that the cam chain tensioner was all in (in the last mark) but I did not change it. After all that the bike had a failure at 1/4 throttle (2500 rev). It sputters and shakes as I accelerate more and more, I feel a lot power but a lot of vibration too.

Question: is it possible that the timing is a little bit off due to this slack?

By the way I check the carb, the plug, the gas, the filter and everything was right.

Yes I would say that a slack camchain can slightly alter the timing, and if its really slack, what is it hitting against? A Yamaha 'expert' will be along soon to help you, in the meantime :welcome:to the HU !

As a matter of fact it is not so noisy, but becasue of this small sputtering someone pointed to the chain since everything else looks fine so far.

Yes, the chain can jump teeth on the cam sprockets if slack and alter your cam timing; easy enough to check if the timing is out by removing the timing cover and lining up the relevant marks and checking the cam position.

It sounds like your timing may be out, but clogged jets in the carb could also cause these symptoms.

Regardless, I'd change your timing chain asap in any case before it snaps and grenades your newly rebuilt engine.

Mine is a different bike, but my cam chain tensioner failed to automatically move in which caused the chain to become slack and the chain to jump a few teeth

The bike stopped due to the timing being seriously out, being a Vstrom and a Vtwin, the pistones were working against eachother

I have new chainbs and tensioners on order

replace that tensioner, it will cause you problems

Cheers
TS

So if I check and the marks are out it means the chain jumped. And if the masks are lined up the timing is ok and the problem is another?

Pity you didn't change the adjuster or more likely, the cam-chain "block" that places tension against the cam-chain when you did the top-end rebuild.

There could definitely be timing issues with a slack cam chain and "tooth jumping" is possible.

If it's an "interference" engine (meaning that the pistons and valves could touch if not time properly), yes, you could have catastrophic failure.

Is there currently cam-chain noise with the adjustment at it's present nearly full-in position ? If so, you need to address this SOON.

There is no noise coming from the cam chain and I dont think it has jumped a teeth either.

Tooth.


Have you checked your carb jets/spring/needle/diaphragm/intake & airbox rubbers?

Yes, tooth. Yes indeed, when I rebuilt the top-end I took the carburator apart to give it a clean-up.

Should I check it again?

Another related question: if the camchain has not jumped a tooth but it really has a slack (last mark of tensioner), can it produce the problem I described above?

In one of the manual I managed to download there are these two images, Which one should I use to give the necesary valves clearance?

Mark 1 in first pic, the one which looks like "I" .NOT the "H"

Make sure you set it on TDC on the compressionstroke. You should see the intakevalves go down and back up, shortly after you'll have tdc on compressionstroke.

Then, what is H mark for?

It will probably tell you in the manual; but if I was a betting man I would postulate it is to do with ignition timing......

If your chain is not noisy, I doubt jumping a tooth is the cause of your problems; the chain needs to be changed all the same, though.

Did the problems just start suddenly one day after it was working OK, or did it never run right after the top end work?

Thanks for answering this fast. No. this problem started just after doing the rebuilt. I just learned a couple of things: 1 I set the valves clearance using the H mark instead of the I mark, 2 I just rode my bike with the choke out and it runs definitely better. (see my other recent post)

I remembered that when I cleaned the carb we put the position of both needles on the last marks just because my spark plug used to be black and some people recommended me to work with the needles and the jets.

I reckon your problem is jetting - too lean, probably.

Try raising the needles one notch at a time and make sure the main jets are clean and your air filters are clean. Do a plug chop after each change of needle height or jets at the relevant throttle position and check the plugs.

Just on a statistical basis, carb problems are far more frequent that cam chains jumping teeth on sprockets.... just sayin'...

Thanks, one more: by plug chop, you exactly mean?

Pilot jet controls fuel flow tickover-one quarter throttle.

Needle position 1/4-3/4 throttle approx.

Main jet 3/4-full throttle.

Run bike on 1-2 mile stretch at appropriate throttle opening and check spark plugs to assess mixture; should be light tan colour, not white (too lean) or black (too rick). Adjust needle position +/- jets accordingly.

I would suggest putting everything back to standard factory including the air filter and start from there; you will likely not have to do anything further.

What about neddle in second carb? Should be in the the same position as the main carb?

An odd thing: I took out the spark plug and is totally with black powder....??? What does this tell me??

Mixture it too rich or you are burning oil or you have the wrong type of spark plug in there, or possibly a mixture of all three.

What is the compression (valve clearances must be in speck) and beware automatic compression release if your bike has it?

I would imagine so, but I am not an expert or even very knowledgeable about dual carb set ups where there are two carbs for one cylinder.

I`m happy to report that I finally managed to solve the problem posted here.

Although, a new one came up; and I`m sure it also has to do with the carb. The bike is starting properly, it keeps at idle as it should (1200 plus revs) at full throttle just fine. Now, the little mishap is that at a sudden stop it goes off, even when pressing the clutch correctly. If I stop slowly, there is no problem at all. Or if I stop suddenly but give a couple of throttle it keeps at idle as normal.

What can I check or do about it?

I will still stick by a loose chain being a problem, but I have since found mine was caused by something totally different, I still changed the chains and tensioners

My problem is here

Cheers
TS

So what was the problem in the end? Did resetting the carbs/jets/needle heights solve it?

Your new problem sounds like your clutch is not disengaging completely - needs adjusting.

The problem was the position of the needles; I adjusted them and and that was fine.

Now, the current minor problem is happening even when I just move the bike forward and use the brakes with a sudden stop not even engaging any gear.

OK, good. If the cam chain is not noisy, forget about it for now.

Now adjust the clutch exactly as per the manual - I suspect this will solve your problem.

I changed the chain anyway. I think you have not read carefully or I did not express myself properly. It is not clutch related since the problem shows up even in neutral just a sudden movement makes the bike go off.

Well, funnily enough, Rich07, I do have better things to do than read every word you post on the internet.

Since my advice does not seem to be appreciated, despite the fact that following it has solved your problem to date, I'm going to refrain from further input to your issues - you can fix your own bloody bike.

Now piss off.

Not on these pages, please
 

Come on, guys! Doc, that was really uncalled-for and not suitable for the best and most helpful Yam-trailbike forum out there. Kindly do us all a favour and delete that post. For the record, I'm sure I speak for more HUBB users than just myself in that we do appreciate your (usual) input.

Rich, I don't currently see your reference to changing the chain - please be more tactful when replying to helpful riders. I don't think you meant to sound rude but short lines of text can be such a blunt instrument.

Er, yeah, I'm expecting (another) infraction for that one, but then again, he probably deserved it given the lack of appreciation for the basic lessons on mechanics that solved his problem that he couldn't be bothered to say "thanks" for, topped off by a fairly obvious ingrate comment.

Oh, well, such is life.....

I apologise if I said or did something wrong. It really wasnt my intention. Since English is not my mother tongue I might have hurt somby's feelings.

Maybe I did not express myself clearly. I appreciate every input of you all I really do.

Im not that kind of person who does not care about others.:(

Hi Rich,

Thanks for that - no worries.

Perhaps I did not appreciate the language barriers, so sorry if I offended you.

Hope the bike works out.

DS

Check the floatheight in the carb, could be the issue if incorrect.

As for the float, what in your experience might be happening? Too high or too low? What's the reason to go off?

My guess is the fuel level is set too high, and overflows when you move the bike around, but im shooting in the dark here.

Uhmm, I have not had the time to do the check but I'll definetely do it, thanks.

Usual cause for the engine to stall when the throttle is closed quickly is an air leak at the manifold. This may be very small so it won't affect normal running although it can sometimes make the bike harder to start or it will need more choke than usual.

If you have something like a Scottoiler connected to the vacuum take off point check the pipe is in good condition. Check any hose clamps are tight and if it's a rubber manifold check there are no splits in it.

Really, really interesting tell me more pls. It does not have any problem starting; I does not even need any choke at all. Scottoiler? what exactly is this?
The four clapms are ok, not leaks at all. one more thing, the bike stalls even in neutral and at iddle, just a sudden push like pushing forward and pulling the brakes makes it stall.

I think you need to adjust your clutch, as per my previous post; it sounds like it is dragging.

Have you tried this, as per the repair manual?

Excuse my ignorance, I do not really understand the issue with the clutch since I have mentioned that the bike stalls even in neutral not driving it.

Let's be clear: you push the bike forward in neutral, stop it with the brakes, and it stalls? I can think of a couple of reasons for that, but I will wait until you confirm this is actually what is happening.

Scottoiler - an automatic chain oiler that feeds oil to the drive chain by gravity, worked by a valve which is actuated by inlet manifold vacuum, so it only delivers oil when the engine is running. A leak in the pipe between the oiler and the inlet would allow air in to the mixture, leading to a weak mixture and possibly running problems.

If your bike will start without choke then something is wrong. It sounds to me like a very rich mixture, which would be confirmed by high fuel consumption and black exhaust smoke and/or soot around the tail pipe.

A plug reading would help narrow this down.

Synchromesh gearbox; cogs are spinning but not engaged on shaft in neutral.

It's a five minute job (or less) - just try it, even if you don't understand it. You don't understand carbs either but my advice solved that problem.....

You push the bike forward in neutral, stop it with the brakes, and it stalls? yes, it is what it does. At any sudden stop it stall, whether in neutral, at any speed, with the clutch pulled. If I want avoid that I just have to engage the clutch and give a couple of (how can I express it?) throttle..??

One more thing, I live in Venezuela; the average temperature is 27 º C and almost every bike need not the choke to start.

Could be an electrical problem - maybe you trapped a wire or slightly dislodged a connector when you last had the tank off

I'm trying to get my head round this. If he just pushes the bike forward while idling, brakes and stalls it, then I would be looking for something electrical. Perhaps a loose connection, a trapped wire, or even a dodgy ignition switch. (I had an issue with my XT where touching either brake caused the engine to stop. I worked out in the end it was a poor connection in the main switch, and the extra load of the brake lights was causing the circuit to open. New switch cured it immediately.)

However, if the bike is stalling after a period of running when the throttle is released (and, of course, the brakes applied ...) such as when exiting a main road or coming to a junction after a faster run, then I would be looking at mixture, worn needles and/or jets, and possible air leaks.

Anyway, that's the best I think I can offer from a cold, wet climate 7500 km away.

You could have knocked the nail on the head Black Dog. The common theme appears to be applying the brakes. As you said, you had the same problem with an XT. Worth a look before tearing carbs etc apart.

Did you fix this already?

Could be. This is an international forum, and I am quite happy to work around language difficulties where I can. But I think I have reached the end of what I can offer here.

OK, guys, a tray to adjust the float neddle and level. I still I got the same problem. I found out something that might give somebody a clue: when I close the petcock valve it does not do stall. So it is not an electric problem.

One question: how petcock is associated with electric stuff?

I have the feeling that you doubt that my problem is real and that Im pulling somebody`s leg. Let me tell Im not. For sure we have the language barrier.

What I meant in my last post is that it is not an electric problem but a problem with the carb.

Well, yeah, it starts to look like that after such a long discussion.

And your topic says "can the cam chain slack produce failures?", and my answer would be very short: YES! If there's slack where it is not supposed to be it not only can, but it will produce failures, and major ones, at some point. So if you do something, do it once, and do it right, or you will have to do it again.

Read your reply once again... Does that make any sense to you?
Sounds to me more like "when I clap my hands my bike doesn't stall, so it is not an electric problem". How does clapping hands and bike's electricity could be related? (unless there's clapping sensors, but let's not go that deep...)

And more "it does not do stall"... So does it stall "does do stall" (grammatically incorrect but my grammar isn't perfect too), or it doesn't stall "it does not stall"???

And yeah, if I close the petcock on my bike it won't run very long too... It needs petrol to run.

I'm not trying to be harsh, I'm trying to understand what you want to say... bier

Carb problem??
 

I'm not sure what is meant by 37 countries in this context, but you guys haven't got out of the start blocks yet for misunderstandings of language, cultural differences of approach in describing issues and how to communicate.

I read this thread more or less every day to see how the multi-cultural, multi-ethnic, multi-religious belief, multi-language (including especially those who do not use English as their native language) individuals are getting along.

Patience is needed (hang in there guys!) and it could just be an issue with the carburettor?
Flooding carb for instance?