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

yamaha42 · Senior Member

Another cam chain noise

TTRfan · Super Guru

The chain is normally only loose like that when it is worn. Did the sprocket marks line up against the head?

I confess that I am not a fan of manual tensioners as they require a fair bit of mechanical know how to set up properly.

Assuming the chain was good, did you take out the tensioner to check it is working properly. It is unusual for them to fail.

Brian

yamaha42 · Senior Member

I should add that the timing chain has proper tension otherwise. It only gets loose if I push on it hard enough to compress the tensioner, since the tensioner wont return unless i pry on the guide.

alanwebbo · Veteran Member

I am not sure that this is a fair test.. I assume the piston is at TDC on the compression stroke when you do this ? if not you are expecting the tensionser to rotate the cams against the valve force of the valve springs. Even if the engine is on TDC, the tensioner would have to rotate the inlet cam. The tensioner is designed to take the slack out of the non- drive side of the chain, heavy loading would wear out the guide very quickly. What happens if you rotate the crank (in the right direction) after doing your test.. Does the tensioner return ? If so all is well.. As Brian says it is not a big job to take it out and check its operation if you are in any doubt.

-- Edited by alanwebbo on Monday 20th of July 2015 10:20:28 PM

yamaha42 · Senior Member

I set it at an unofficial TDC- the lobes weren't pressing the valves, but I never checked the mark on the flywheel. I shall do it properly before I ride again and then report back to you guys.

66T · Veteran Member

TTRfan wrote:
The chain is normally only loose like that when it is worn. Did the sprocket marks line up against the head?
I confess that I am not a fan of manual tensioners as they require a fair bit of mechanical know how to set up properly.
Assuming the chain was good, did you take out the tensioner to check it is working properly. It is unusual for them to fail.
Brian

Not trying to be smart, Brian, but I've replaced at least three tensioners in my poor old TTR (lost count). Also, I've kept each one alive for a bit longer by removing them and looking for the polished slip mark on the push rods, then roughing the areas with fine wet and dry. If it'd been really hot weather, I'd pull them apart and add a touch more spring tension.

At my work, most people are starting to get TTR cam chain rattles around 20-25000 km. This equates to roughly 1000hrs of engine time. Somehow, and sadly, I'm rougher on tensioners than most people. (<15000km/750hrs for my WR250R...).

So I've gone the manual route, which has been on there for around 15k I think. Maybe more. Easy enough to set up as long as the chain rattles a bit when the engine is cold. I set mine when the engine is really hot, by backing it off if necessary until the chain rattles, then screw the push rod in until the rattle goes away. Surprising how small the adjustment between rattle and quiet is!