Thread: Piston ring help. pro x

i have just striped the top end down the the conrod.
I have a new pro x piston ready for its new rings.

I have 2 main piston rings. one black with "N" stamped on it and another copper coloured ring with nothing on it.

I have also an oil control ring set up which has 2 slim rings and a sping type ring that goes inbetween( i asume)

My Question is.

which ring goes on top. the black or copper ring???

There is only one slot and TWO rings..

why is there a spare....

the u have to carfully put the two really thin ones in the same slot as the spring one

yeah I think there may have been a mistake in the packaging . I have used the black larger ring with N stamped on it.

First time I have tackled a job so big on the bike.

It is all back together now. It feels a little tight in the bore. She stalled twice on low revs . I guess this is a result of rings needing a run in.


Im guessing a few hours on forest fire roads will be a perfect way to run in the new parts.

tis a fantastic bit of engineering under the skin. Very enjoyable project.

What ring gap did you set the ring to? I use 0.1mm for every inch of bore.

Plenty of closed throttle whilst running in will keep the rings lubed.

Originally Posted by KevInYorks

What ring gap did you set the ring to? I use 0.1mm for every inch of bore.

Plenty of closed throttle whilst running in will keep the rings lubed.

? opps. dont know what this is. I used the repair manual in the members section. Did not see anything on ring gap.

i used the slightly larger ring as I have a little wear on the bore up top.

I had her out on fire roads today ... Start of the day she felt tight. But 2 hours of low rev and closed throttle riding, she was feeling better.

The reson I changed the piston was because it was recommended in forums.

I could not see any visable wear on the old piston. the skirt was worn, but what difference would that make?

I hate running shit in. BBBBBBooooreing

i used the slightly larger ring as I have a little wear on the bore up top.

ring gap is when you put the rings inside the cylinder then measure the gap between the ring ends with feller gauges, you then need to file the edges of the rings to get the proper spec. I would say more than half people that replace their top ends don't know about this procedure, the reason for this is that they make the rings slightly bigger to compensate for cylinder wear. you should be ok, ihaven''t heard of anyone that never filed the rings having problems, may jsut be a little tight but should wear in, the second ring they gave you is probably an oversized ring in case the ring gap is out of spec due to cylinder bore wear

You need to measure ring end gap throughout the stroke of the piston in the bore though.

Originally Posted by Revolution

You need to measure ring end gap throughout the stroke of the piston in the bore though.

Thats right, in case the bore is tapered/uneven wear