LiftdT4R Posted January 20, 2010 Report Share Posted January 20, 2010 Hey, I pulled this piston out of a bike I'm parting out, and I never saw one like this before. It says WSM on the inside and it looks to be painted inside the castings. I'm guessing it's made by WSM but I've never heard of them. Are these pistons any good? I was also wondering what would cause this piston to drag or slap the inside of the cylinders, you can see the marks on the piston as well as the cylinder bore. Quote Link to comment Share on other sites More sharing options...
KlotzBanshee Posted January 20, 2010 Report Share Posted January 20, 2010 It looks like a stock one to me other than the WSM cast into the inner skirt. I'm going to go out on a limb here and say its a cast aluminum WSM stock spec replacement piston? lol Quote Link to comment Share on other sites More sharing options...
papa_smurf49319 Posted January 21, 2010 Report Share Posted January 21, 2010 x2. How long have those pistons been run in the engine? The wear doesnt look to terrible! Quote Link to comment Share on other sites More sharing options...
AKheathen Posted January 21, 2010 Report Share Posted January 21, 2010 yup, that's a cast wsm replacement, and it was coated, too. i don't think that was the wsm, or swaintech coating. the look of the crown could either be ceramic, or someone hit it with the wire wheel. Quote Link to comment Share on other sites More sharing options...
LiftdT4R Posted January 21, 2010 Author Report Share Posted January 21, 2010 yup, that's a cast wsm replacement, and it was coated, too. i don't think that was the wsm, or swaintech coating. the look of the crown could either be ceramic, or someone hit it with the wire wheel. Awesome, sounds good, thanks for the info!! What would cause the piston to hit the sides of the cylinder like you see in the pics above? Was the bore done wrong or is it a piston issue? I think it's called piston slap right? Quote Link to comment Share on other sites More sharing options...
AKheathen Posted January 21, 2010 Report Share Posted January 21, 2010 i don't see what you are talking about "hitting". piston slap is where the piston crown taps the dome. are you talking about the scraping on the sides? that's probably a combination of dry starts, dirt/dust, and likely either starting. also, not warmming it up before riding hard can scrub the walls like that. Quote Link to comment Share on other sites More sharing options...
shanYE west Posted January 22, 2010 Report Share Posted January 22, 2010 We've always considered piston slap a loose bore.. (skits slaping the walls) Which could be possible if the pistons were installed into cylinders that were setup for forged pistons. The casted pistons tend to be more resilient against cold seize since they dont swell like the forged pistons do, hence the tighter tolerances. As long as the bore was properly setup you shouldn't get piston slap. Pistons dont look too bad.. I've seen worse. Mic'em out and see what the specs are. WSM are good pistons. I wouldn't worry about the quality of them.. I'd be more concerned with the bore specs. Quote Link to comment Share on other sites More sharing options...
LiftdT4R Posted January 22, 2010 Author Report Share Posted January 22, 2010 Thanks for the reply, that's good info!! These are from a bike I'm parting out, and I have no intention of running them. The problem here was there was 1 Wiseco piston, and 1 WSM piston in the bike. I believe one is forged and the other is machined. Not sure why the PO used 2 different pistons. The cylinder this piston came out of had the dome pretty well chewed up and only made 100PSI, while the other cylinder had 125PSI and a Wiseco piston in it. I'm guessing that the bores were indeed setup for machined pistons but the PO used this one by accident, or didn;t care which caused the bore to wear out prematurely. I usually like to check out the good the bad and the ugly when I part out bikes at least for my own education so I don't do the same thing when I rebuild mine. Thanks again fort he info!!! Quote Link to comment Share on other sites More sharing options...
AKheathen Posted January 22, 2010 Report Share Posted January 22, 2010 well, in the automotive industry and schooling, piston slap is where the piston slaps the dome either from rocking bearings, or carbon. such as the isuzu built vortechs would do in really cold temps because of the piston design. i suppose the skirt slap could fall in the same category, although it's always just been piston rock to me. my tahoe does it almost daily in the winter. sounds like someone repplaced just the one piston because of a failure, and not the other. i also have a stock head that has been beat up. i'm gonna get it cut for 4mill sometime, but you couldn't sell it as-is, as you probably already figured. Quote Link to comment Share on other sites More sharing options...
LiftdT4R Posted January 23, 2010 Author Report Share Posted January 23, 2010 Good to know about piston/skirt slap. I went to school for engineering but unfortunately it was civil, so I'm not really familiar with any automotive terms. I figured the head wasn't worth anything, I usually don't sell them anyway, I hang them on the wall in my shop. I'm up to 8 now. Both cylinders are on the same bore, 0.50 over, so I'm not sure why 2 different pistons were used. Would that be the most liekly explanation for the low compression? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.