2006 Sy250R Chain Tension

[j__h]

My very minimal manual says nothing about how to check the chain tension. Also being new to trials bikes (and bikes with tensioners) I am not sure about the spec. Anybody have any word on how to best set this? I hear often a measure of the tensioner to swingarm distance is the spec.

This is the bike on a stand:

This is the bike on the ground:

[feetupfun]

It is important to protect the gearbox bearing and the chain from overload by making sure that when the sprocket centre, swingarm pivot centre and the axle centre are all aligned, that there is still a bit of free play in the chain.

The other end of the scale (too loose) on your bike would be if the tensioner is going high enough to touch the swingarm when the suspension is fully extended.

If you set yours between these two extremes, you will have a happy chain

The ideal measurement you are asking about (the distance between the tensioner and the swingarm) will vary with different size sprockets and where in the stroke of the suspension you are taking the measurement, so there is no single correct dimension for a given bike unless you specify those variables.

[firebladepully]

I was advised to aim for a gap of approx 10-13mm (3/8" - 1/2").

I simply use my little finger and slide it in between the swingarm and tensioner rubber for a nice sliding fit. Never had any issues on any of my Scorpa's SY or SR doing this and i am using the std gearing/sprockets.

Do make sure though that your tensioner is in good state of wear, ....the std alloy ones do wear and bend easily.

Feetup has more or less hit the nail on the head with his explanation too :-)

Edited May 15, 2014 by firebladepully

[j__h]

Thanks for the advice.

Yes, it does make sense it would be sprocket sensitive just thought it would be a wide enough margin that some simple measure could be done. (I do know the Golden standard is that the chain does not get tight anywhere in the bikes travel.

>Do make sure though that your tensioner is in good state of wear, ....the std alloy ones do wear and bend easily.

The bike I got was barely used and the tensioner appear to be in good shape.

The last question is: it does appear the midpipe gets touched by the chain sometimes (I can see some small marks where the chain runs under it) Is this something that is normal? Would not want to punch a hole in the mid-pipe. The chain was actually a little bit looser than the picture I took, I had just tightened it a little bit to what seemed right, maybe that would keep it off totally.

[firebladepully]

Sounds to me like the the chain has either been too slack at some point or stretched/worn bad and has been jumping the front sprocket, hence hitting the underside of the mid silencer box.

I have never had that occur to my SY, but not saying it doesnt happen. A worn front sprocket can also cause the chain to ride up the teeth and jump, again would be likely to hit the mid silencer box.

Another check would be to look at the mid box ans see if it is correctly seated onto the front pipe and back silencer. The space is tight at best of times around the mid box and it usually rubs on the underside against the engine casing right near the rear engine/swingarm mounting area.

[j__h]

The chain and sprockets are in good condition. The tensioner block was just off the swingarm when on a stand, did look like it could use a bit more chain tension. The picture above was after a bit of tensioning of the chain.

How far should the midbox be pushed onto the header pipe, there is not really any defined point to stop?

One note is that the marks on the midpipe would be easy to miss if one were not looking for them.

Edited May 21, 2014 by j__h

[firebladepully]

I am pretty sure the front pipe will hit the the stop inside the mid box, same for the rear silencer. I would put mid box onto front pipe first, then rear silencer into mid box.

You will find that once this is done and all is tightened up, you may be able to twist the mid box side to side to give a bigger gap between chain run and bottom of mid box, but do check nothing else is rubbing or hitting against the mid box ( shocker, carb etc). I know it is pretty snug in there.

Hope this helps sort it :-)

[j__h]

I have seen inside the midpipe and there is not any stop for the header, just two large orings then it goes into the midpipe itself.

>You will find that once this is done and all is tightened up, you may be able to twist the mid box side to side to give a bigger gap between chain run

I will give this a shot, hopefully just the tighter chain will help and maybe some extra margin can be from the twisting of the midpipe.