How to adjust cam chain tensioner on GPX 250?

[Brendonv]

Hey guys i bought a GPX 250. It runs great apart from one thing, it has a rattling chain sound on de acceleration which i suspect is a loose cam chain. I read up on how to adjust it, however mine is slightly different. It has an extra bolt which i think is an adjusting nut. There suppose to have automatic tensioners but i think this might have a manual tensioner.

Ive included a photo of it. If i first loosen off both locking nuts then turn that bolt in will it push the rod down which tensions the chain? If not how do i adjust the tensioner?

Thanks,
Brendon

[richarde]

Looks like a GD Engineering job

Gav (GD Engineering on here) puts these manual tensioners on, because the automatic tensioners are useless. I'm pretty sure the lower bolt you have circled is just a blanking bolt and doesn't do anything.

Pretty much got it in one. Loosen the locknut (the middle one you have circled), and tighten down the adjuster. Make sure you don't do it up too tight. If you do it with the engine running you can mess around with the revs to hear the difference so you have a better idea of what is correct adjustment.

[Brendonv]

Alrighty, yer it didnt look standard. So do i just do it up till its pretty firm. Is its better to do it while the engine is running? I guess like you said you can gauge it better while its running i just dont want it to go crash bang pop.

Ill give it a shot tomorrow (dont think the neighbours will like me cranking it up for 5mins now, plus ill gas myself in my shed).

Cheers for the reply.

[Xuaxace]

Alrighty, yer it didnt look standard. So do i just do it up till its pretty firm. Should its better to do while the engine is running? I guess like you said you can gauge it better while its running i just dont want it to go crash bang pop.

Ill give it a shot tomorrow (dont think the neighbours will like me cranking it up for 5mins now, plus ill gas myself in my shed).

Cheers for the reply.

I just tensioned mine (ZZR) last week, same type made by gavin. I wasn't so sure of how tight I should tighten it, so I went little by little (with the engine off) untill there was no rattling sound (I turned it on a3 3 times to check). Hopefully I didn't overtighten it though, first time doing that.

[Brendonv]

Im pretty sure u will be able to tell if its to tight since the engine would seem a bit sluggish. Im just going to tighten till taught then back it off slightly. Hopefully it works.

[richarde]

The way Gav did it on my sister's bike is to tighten it while the engine is running, and if you have the locknut backed off, then as you get close to the right adjustment, you can hear the difference it makes to the rattly cam-chain noise when you apply pressure to the bolt with your finger. Hard to explain, but basically you should be able to hear the difference when you get it adjusted up.

Just adjust it until the noise disappears, then back it off slightly. If you are worried about it maybe PM GD Engineering and ask him, or send him a link to this thread and ask him to comment.

[Frogger]

gav is on holiday atm , i got one of these from him and i remember he told me make sure i dont over tighten it as it will shread the shit out of something. i think the guides for the cam chain but cant remember.

the screw on the side is from the old auto tensioning setup u press the spring in and that screw holds it then once its back on the bike u loosen the screen till the spring is released then tighten it again.

[GD Engineering (Gavin)]

Loosen the bottom nut with the engine running at idle, screw the bolt down clockwise ( should only need your fingers ) until the noise JUST stops.Give the throttle a blip and make sure there is no noise on over-run and tighten it back up again. Don't over do it or it will kill the tensioner blade and guide........ if the motor labours at idle since the adjustment, you have gone way too far.