What size piston to order...

[railer]

Did some searching, couldn't find what I was looking for.

'98 RM 125 need to rebuild top end, but am not sure what size piston to order. I need to order a wiseco flat-top and on DK website, they're listed by bore size. After measuring bore with a caliper, the bore is 54.00mm. I just want to make sure that I am ordering the right thing...

http://www.denniskirk.com/jsp/produ...Id=&productId=p755M05400&leafCatId=&mmyId=104

Please advise...

Thanks, y'all.

Brian.

 

[upstateny]

IF you have the Old Piston, put it in the bore, and check the slop that you have. I believe those are Nickasil plated also. If the bore has any visible marring, you will need to either get another cylinder, or have an Iron Sleeve put in the existing cylinder. If the bore is not worn extensively I would put what ever is the Stock size is in the engine.

 

[julien_d]

If the bore has any visible marring, you will need to either get another cylinder, or have an Iron Sleeve put in the existing cylinder.

A better option than either of those is replating the existing cylinder, assuming there is damage to the existing plating. IMO sleeving should only be considered as an alternative to welding and replating to save some money. The cylinder would only need welding if it had deep gouges that go into the aluminum bore, or cracked bridges, etc. Likewise, I'd only recommend a "new" cylinder if you're sitting on loads of cash you'd like to blow. Most of the times the plating used when replating is harder and will last longer than the factory nikisil plating.

Assuming all is well with your cylinder, you just need the correct piston for the stock bore. 54.0mm if you're buying wiseco.

 

[railer]

I think you've misunderstood my question. The cylinder has no damage whatsoever. It doesn't need to be re-sleeved or honed or anything. The bike ran like a champ before I decided to do a top-end, but I just wanted to do it becuase it has a lot of hours on this piston. I'm just trying to make sure I order the right size piston. The bore size is exactly 54.00mm which I would assume is the stock size. You can order pistons in bore sizes up to like 56mm in .5mm incriments. The lowest is 54.00 so I would assume that is the piston I need to order. I just want to make sure I'm not missing anything, ya know...first top-end rebuild, so trying to make sure I do it right. :)

julien answered my question, though.

Thanks.