PW50 Piston Rings

..... · Quote Me Happy Joined: 15 Jan 2005 Karma :

Hello,

I've got a little PW50 that needs a piston and ring change. All pretty straightforward but the kit I've received has three rings - two normal rings and a very thin, flexible ring. I presume the very thin ring must sit behind one of the other rings but which one?

The parts diagram I looked at made no reference to the thin ring, although it was for a later bike but I believe the design is the same since the start of production.

Thanks chaps.

https://www.bikechatforums.com/files/picture56835sdfgh.jpg

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
the thinner, flexible ring is the expander ring.
this fits in the bottom groove, before the actual ring,
make sure you get the main rings round the right way (the top ring is the "keystone" ring, & if they are stamped with a letter, make sure the leter is facing up..
cheers,
GAZ

ms51ves3 · Super Spammer Joined: 08 Jun 2007 Karma :

If you search Google you will find many debates on whether the expander ring is any use. A lot of people leave them out.

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
tbh, i have left them out umpteen times & its never caused any problems.
but if the kit comes with an expander ring, then i'l usally stick it in, just for the hell of it.
never really understood its purpose.
cheers,
GAZ

..... · Quote Me Happy Joined: 15 Jan 2005 Karma :

Thanks for the help Thumbs Up

I have hit another problem though - I've measured both rings with vernier calipers and they are the same size. The ring goes into the bottom groove of the piston no problems, the other top groove seems too tight and the ring doesn't seem to seat correctly. Is it a case of just squeezing it in harder? I didn't want to try as I might damage it.

Cheers.

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
have you got them in the right grooves?
i know you say you have measured them, but some rings are groove specific, due to minute differences to the shape/profile.
are the letters facing the right way?
does the piston have locating pegs & are the rings sitting correctly at them.
some rings are hard to hold in, almost cutting your hands, there is a tool for doing this, but i've never had to use one.
you sure you got the correct rings?
did it come as a kit?
cheers,
GAZ

Damon · World Chat Champion Joined: 24 Aug 2007 Karma :

as above, there are normally locating pins that need to be positioned at the opening of the piston ring.

..... · Quote Me Happy Joined: 15 Jan 2005 Karma :

There were locating pins but the rings didn't physically fit in the grooves. Got it sorted in the end thanks to Tatters with a half bodge using the old piston,an old ring and a new ring.

Seems to have sorted it for now - I'll wait for it to blow up then have it rebored with a piston to match.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Often one ring is slightly wedge shaped. Hence measure the heights and they are the same, but the heights in the inside edge are different.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

tatters · Exxon Valdez Joined: 05 Jan 2004 Karma :

Shitty pattern piston kits for lawn mower engines both rings were the same, the cyclinder was slighty scored and well worn so just used a new top ring on the old piston should get a few hours more out of it till it blows. was quite supprised the piston slapping stopped with one new ring.
____________________
Past:NRG50,AF1125(x2),NSR125RR,ZZR250,CX500,VFR400,KR1S,ZZR600(x2),CB400N,YZF1000(x2),KH125,Z200,FX400R,CBR954RR(x2)GPZ500S,GT550,VFR750F(x2),RD350N,XR650R,CBR600F,CB250,KDX250,YZF750R,CRM250,400EXC,KLR650,TTR600RE,DR350S,R100GSPD,RGV250,VMAX1200,DL650,KZ750 Present:G650XC,C12,CRF450X,1190ADV

temeluchus · World Chat Champion Joined: 01 Oct 2008 Karma :

https://www.federalmogul.com/korihandbook/en/index.htm
____________________
Some shite cruiser. Now with guns and FREEDOM!