A forum for owners of Yamaha TTR250 trail and enduro bikes!

TonyB479 · Member

Installing a manual cam chain tensioner on a 2000 TTR 250 US model

alanwebbo · Veteran Member

I can only imagine the generic instructions include models that have a chain guide between the cams. This would have to be removed to check the tension on the chain.. The instructions would be better if they said " replace guide after setting chain tension"
Anyway.. There is no such cam chain guide on a TTR between cams.

TonyB479 · Member

That's what I was thinking but wanted some solid advise, this forum is awesome for the do it yourselfer like me and I appreciate the response. I am certain there will be many more questions from me.

locky · Guru

I also agree. When fitting the original tensioner you hold off the tension with a short screwdriver, then when it's fitted you remove the short screwdriver and it auto tensions. This is no different to manually tensioning it your self.

66T · Veteran Member

I didn't notice this thread until today. I have had a manual tensioner installed in my TTR for a while now, and have learned quite bit by trial and error, and from Krieger in the USA. I have one of his tensioners in my WR250R, but that's only been in for about 7000km.

The biggest error is running the tensioner too tight. The cam chain must rattle slightly when the engine is cold, which is bloody annoying but necessary to get reasonable life from the chain, bearing areas, tensioner blades etc.

The rattle should disappear completely when the engine is hot, thus the tensioner setting should be made then. There is no guesswork - gently screw the tensioner out until there is a noticeable rattle. Then screw it in (again gently) until the rattle just disappears, and lock the nut. On both my bikes, it took some time before the tensioner blade material conformed with the push rod ends, so there was some fiddling for a while until things settled.

I've discovered that a slightly loose cam chain will last for a very long time, but like a drive chain, if it's too tight there can be dire consequences. I can live with slight rattle, but not with having to replace the auto tensioner. I have four rooted ones so far... This is a consequence of operating the poor bikes for long periods of slow running, interspersed with full throttle and rpm then shutting down, and weather conditions from around 0degC to upper 40s. Poor me too, come to think of it!! Bloody idiot.

As an aside (and I've yet to receive confirmation), a member of XT660.com has covered 98,000 miles on his Tenere travelling the world (I think), and has yet to replace his cam chain. I put this down to the fact that XT660s seem to run minimal tensioner pressure. Just enough to stop clatter. Mine is like that, anyway.

End of book. Sorry...

TonyB479 · Member

Thanks for the reply 66T, I really appreciate the advice. I finally managed to get all of the things done that have kept me from applying myself to getting the bike back up and running (we live on a farm and there is a lot to do) This weekend I should have the top end back together and I will use your info for snugging the chain when it's hot. Thanks again!

locky · Guru

Are the standard tensioners reliable ?

TonyB479 · Member

I am probably not the right person to reply to this but..

My reason for using the manua- tensioner is based primarily on availability of the auto-tensioner, unfortunately they are difficult to locate and if you are so lucky the cost is double that of a manual one and all I could find were used. From what I understand the spring in the auto-tensioner can over time loose strength so I didn't want to chance a possible replacement in the near future.

66T · Veteran Member

locky wrote:
Are the standard tensioners reliable ?

Short answer: no. For my use, anyway. Good thing about the manual version is that it will never have to be replaced👍🏽✔️

locky · Guru

When and why do the originals fail ? Is it time or mileage twhen they fail ?

66T · Veteran Member

The very worst thing for cam chain tensioners is, I believe, pulling rev-limiter revs then shutting the throttle. The shock loading on the back (tensioner) side of the chain puts sudden pressure on the poor tensioner. It'll usually take some abuse like this, but eventually can't handle it and slips. Once it's started to slip (and I hope the experts on the forum will back me here), it will continue to do so increasingly often.

Also, I think that extended periods of slow running upset tensioners, probably because the engine gets really, really hot and thus expands more than it should. This puts strain on the chain and, of course, the tensioner.

Normal operation in cooler climates should see tensioners last very well. Naturally, if you're rough/abusive/unfair on your engines, such as those in working motorbikes, they lead a much shorter life.

alanwebbo · Veteran Member

Sorry 66t, i cant agree with your thermal expansion theory. A few quick sums suggests that even if you got the barrel to 200 deg c the expansion would be around 0.005 mm. ( 1/5th of a thou in old money). Although the expansion rate of the steel chain is half that of aluminium barrel, the chain is much more than twice as long as the barrel (and as the man that tried to pick up Hailwoods chain when it broke whilst racing ago on the IOM found out, the chain will be hotter) so in practice there will be very little different in chain tension due to temperature.
I agree that snapping the throttle shut shock loads the tensioner, but if it is a manual version this will result in high wear on the tensioner blade.
I think i will still with the spring loaded one.

66T · Veteran Member

I respect your ability and understand your argument, alanwebbo.

However, the reality is that when the engine is at its hottest, a manual tensioner should then be adjusted, which means a quiet chain.

When that engine cools, and the engine re-started, that chain will rattle until the engine reaches the setting temperature. This is indisputable. Thus the expansion is significant, I believe.

Also, I believe that the manual tensioner can't cause excess wear on the tensioner blade under deceleration (when correctly adjusted). It is designed to stop the blade moving, as is the auto tensioner. If a tensioner lets go, there is a real risk of the chain skipping teeth. Believe me, the original tensioner does not allow any blade movement either, unless that tensioner fails.

I think verification of the above can be made by contacting www.kriegercamchaintensioners.com

Mr Krieger makes the things, and issues detailed instructions to each of his buyers.

But your opinions are yours to make, and so is the type of tensioner you choose.

Cheers mate.

alanwebbo · Veteran Member

Thanks 66t

The point i was making is that thermal expansion is not massive.. Even your man tells us that 6 thou clearance on the adjuster may be on the loose side.

The adjustment of a manual tensioner is simple and is printed here in directions that are on the page "About Tensioners". Take a look to see how to do it right. Don't risk ruining an engine with the mechanically poor adjustment techniques posted out there, no matter how well intentioned the posters may be. As I've mentioned before, from the mechanical point of view I'd rather run just a tiny bit loose than too tight. With the methods in our instructions, you will be very near ideal adjustment erring to the loose side if any and only by a few thousandths of an inch (one full turn of an M8-1.25 bolt is .050", so 1/8 turn is about .006", not enough chain play to cause any apprieciable wear and far less play than any failing OEM tensioner).

However chain wear is considerably more as you can see from Brian's photo. So in my opinion the choice is simple

either you develop the skills to set a manual tension correctly and make it part of a regular maintenance routine as the chain stretches..

or you trust the Yamaha tensioner to do it's job.

I haven't owned my TTR long enough to have a problem, but I gather Brian's experience is that the Yamaha tensioner is quite reliable.

As you say it is up the owner to decide.

66T · Veteran Member

You're quite correct that expansion isn't massive, but it's enough to overtighten the camchain if a manual tensioner is set incorrectly, which is my point.

Thing is, as I stated, for my use the stock tensioners fail early. If they didn't, I wouldn't bother about changing them. I envy those of you who aren't plagued with irritating issues like this, but to be fair the bikes are employed as work tools and are subject to necessary abuse. So we have to expect these things.

My WR250R tensioner failed at about 8000km only. Dismal. Hence the Krieger option. Sigh.

To be pedantic, I'm a believer that if you're using a manual tensioner, you adjust it as required rather than do it at a scheduled service. Once the things have settled, they don't seem to need doing very often.

-- Edited by 66T on Friday 31st of July 2015 04:14:30 AM