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

boredus · Veteran Member

Cam chain movement - turning the engine over backwards

TTRfan · Super Guru

Hi Ian

My guess is that the blob of weld on the tensioner was a bodged way of trying to take slack out of a worn cam chain

You are on the money - as long as the "slippers and cam gears are in good shape (any wear or damage will be obvious) then a new camchain (£25) and second-hand tensioner should put you right wink

Brian

boredus · Veteran Member

Thanks Brian,

I have sent over a mail to sales@ttr re the tensioner.

Ian

boredus · Veteran Member

Just a little update on this one.

The new chain and good 2nd hand tensioner (thanks Brian) are fitted and now the engine turns over perfectly. I had the 2 chains laid out on the bench and the old one does appear to be a couple of mm longer than the new one.

I didnt realise they could stretch this much or its not the right chain for this bike.

Here is a pic of the difference in the tensioners :

brindabella · Senior Member

hey, boredus (or anyone with a dud cam chain tensioner lying around),
care to try an experiment....

first some observations:

1. the TTR tensioner is simple, automatic and should be no problem at all;
2. apparently some people replace them regularly
(eg after 48,000km cam chain replaced for first time and tensioner replaced for THIRD time;
3. for some reason there is a manual aftermarket tensioner (just screw in, no spring?).

so what on earth could ever go wrong with the tensioner..
-maybe the spring weakens or breaks??
-maybe the mechanism (whatever is on the end of that central screw) wears and obstructs free movement?
-maybe people blame the tensioner when really they should have replaced the cam chain?

ok the experiment (post mortem): if you prise off that clip and pull it apart, or hacksaw it to look at the tensioner innards,
is there any clue as to what wears or weakens?

BTW I can hardly believe that someone would be so rough as to weld a blob on the tensioner tip!!
It seems like there's a hell of a lot of TTR problems that we see in this forum that can be blamed on the gross neglect of previous owners leaving their bikes in the weather for years, totally ignoring servicing, and repairing in a ham fisted way stuff with hammers and chisels while drunk.

Too bad that bikes serviced and ridden normally that last for ages with no problems (ie most of them) just hide under the forum radar.

barra8 · Guru

TTRfan wrote:
I have only ever seen one manual timing chain tensioner fitted to a TTR engine and I wasn't that impressed

My god That looks nothing like mine

Heres a good one that should makes things better Brian wink

Still a little muddy though smile

NEW READY TO INSTALL. VERY SIMPLE DESIGN. EASY TO USE. COMES WITH GASKET & MOUNTING INSTRUCTIONS.

- THIS IS ON HAND, IN STOCK. WE CAN SHIP NOW!! WE SHIP VERY FAST!

THIS FITS YAMAHA:

- 1999 to 2006 TTR250

location: shelf # (T-1000 @ k)

REPLACE THAT OLD AUTOMATIC TENSIONER THAT WILL EVENTUALLY FAIL YOU. HAVE COMFORT KNOWING THIS ONE CAN NOT COLLAPSE UNDER STRESS.

- CHEAPER THAN A NEW STOCK AUTOMATIC / PROBLEMATIC TENSIONER.

THIS MANUAL CAM CHAIN TENSIONER IS DESIGNED TO REPLACE THE AUTOMATIC AND HYDRAULIC TENSIONERS ON HIGH PERFORMANCE ENGINES. THE AUTOMATIC ADJUSTERS CAN BACK OUT WHEN THE THROTTLE IS CLOSED SUDDENLY AT HIGH RPM. THIS ALLOWS THE CAMS TO GO MOMENTARILY OUT OF TIME, AND CAN RESULT IN BENT VALVES AND SERIOUS ENGINE DAMAGE. HYDRAULIC TENSIONERS HAVE A TENDENCY TO PUT TOO MUCH TENSION ON THE CHAIN GUIDE UNDER HIGH RPM (HIGH OIL PRESSURE CONDITIONS), RESULTING IN PREMATURE WEAR. BOTH PROBLEMS CAN BE ELIMINATED WITH THE INSTALLATION OF THIS MANUAL TENSIONER. NO MATTER WHAT THE ENGINE DOES, THE CAM CHAIN TENSION WILL REMAIN CONSTANT. THIS MANUAL CAM CHAIN TENSIONER IS A MUST FOR ANY KIND OF PERFORMANCE RIDING. THIS MANUAL TENSIONER IS CNC MACHINED FROM BILLET ALLOY TO EXACT TOLERANCES FOR PERFECT FIT.

1252652?AWSAccessKeyId=1XXJBWHKN0QBQS6TGPG2&Expires=1359590400&Signature=XWfzKVwCJcr1cemyo7XQ380UugY%3D

.............................

Jarrah.

-- Edited by barra8 on Tuesday 22nd of January 2013 06:22:46 PM

TTRfan · Super Guru

I have only ever seen one manual timing chain tensioner fitted to a TTR engine and I wasn't that impressed bleh

Timing chain tensioner 002.jpg

boredus · Veteran Member

We get the same ones here on Ebay. The thing with the manual tensioner is just how tight do you need to make it?

barra8 · Guru

boredus wrote:
We get the same ones here on Ebay. The thing with the manual tensioner is just how tight do you need to make it?
..............................................................................................................................................................................................
Taken from my rebuild thread ...
Anyway time to install the manual cam chain adjuster. This is a bit tricky & i had to double checked it (ten times :). When you set the tension you screw it in finger tight & measure how much play is in the chain when pushed down between the camshafts. The play has to be roughly 2-5mm. Do not overtighten or wear & damage will be the result.
I would'nt worry too much....if it rattles a little when it's together you can always nip it up a bit. If you push down there should be a little slack but not much. (not like a final drive chain)
What i like most about apart from what is says in my last post is that even if your chain is a little worn you can still tighten it up to compensate. Also it does not stress the chain when acceleration is let off because the tension always stays the same.

-- Edited by barra8 on Thursday 24th of January 2013 02:33:32 PM