SRX 608 overbore piston rings

[LoCo]

Hi just registered so greetings! 

I have an issue with a Srx 608 twin shock, needs to be rebored (currently 96mm as stock) so to 97mm I guess, I was really not wanting to go down the route of replacement piston and the associated cost along with the fact that if that was done I may as well take it out a bit further to  get a touch more power but would need a new conrod, headwork etc etc.

The question is yamaha offer the over bore rings (2nd     1JK-11610-20 ) & (4th 1JK-11610-40) what is the increase in bore for these? and can they be fitted to the current 96mm piston?

Apologies in advance if this is a daft question ;-)

[guest564]

If you bore it you will need a bigger piston otherwise the piston will rock in the bore and be damaged.

[Steve Lake]

Best bet is a proper rebore, new wiseco piston (which comes with rings and gugeon pin)... you won't need to 'gap' the rings... I've always found them to be spot on.

and CHANGE THE OIL PUMP!!!... your new bore will need a good and plentiful supply of oil... and ANY wear in your pump will cause a premature 'pinch up'.... its definitely false economy to retain the old pump... ok... it's a £100.... but then a second rebore/piston is a lot more!

[LoCo]

Cheers both, yes knew about the oil pump as both the SRX barrel and the grizzly spare engines barrell are both scored due to the back of the barrel getting hot as the pumps went.
Though that was probably the answer re. the rings on 2nd overbore, new piston, gudgeon etc it is then!

[themoudie]

Aye LoCo,

Welcome. 

As SteveL suggests there is only one way to go and that is a rebore plus new piston and a new oil pump, unless you are nifty with engineering and machining and replace the 'non-standard' oil seals in the pump, with 'standard' off the shelf ones.
Also, I had to adjust the ring gap when I installed the new piston and rings, not by much, but they still needed adjusting.
Returned Sally from a 632cc max overbore to a 598cc, with a Wiseco Grizzly liner and piston from Eastwoods (Vic Eastwood, ex scrambler).
To do anything else is a waste of your hard earned cash and time.
All the best and hope you get sorted.
My regards, Bill

[Steve Lake]

I agree with bill ( hi Bill, how's it a goin? ).. with regard to Seal replacement in the oil pump... cettainly the pump can be machined to accept a seal which is readily available (mentioned somewhere within the bowels of this site) and the job works well... as long as your ONLY problem is hardened and cracked seals... but if there is ANY signs of wear or scoring, however miniscule... sling it...
also.. the pumps now available are a higher capacity than the originals... well worth the investment... then regular oil changes complete with filter (I also use a magnetic sump plug) and you will have no further problems with the pump

[themoudie]

Aye Steve,

Nae bother, thank you. Duke rebuild is moving on, hope to be running this year, bikes 40th and my **th! May put some images of 'guts' on more appropriate page.

Hope you get sorted LoCo.

My regards, Bill.