BannedCR500Riders.com

So I am about to do a top end on my 01, but I am not sure what piston to order. The bike currently has a wiseco. I took the piston down to my local shop to have them measure it (same shop that's doing the honing) and it measured out to 90.25. Wiseco doesn't make a 90.25, as far as I know. What do I have? Does a 90.5 piston actually measure 90.5, or is it smaller to account for thermal expansion? If that is the case, what would I order if i want a cast piston?

Thanks in advance for any help.

Probably a pro-x or some other cast piston.. wiseco's usually go in .5 increments so 90 then 90.5 then yer screwed for wiseco. You can get forged pistons up to 91 so you have a bit of room before a resleave. Also most pistons stamp/cast their model number and name and whatnot inside the piston under the dome.

wiseco, vertex, prox and rocky cycle all made pistons that size

wiseco made a 90.25 i thought wiseco only did .5 sizes? learn sumtin new

It's one of those obscure economey trick things. Get the cylinder bored over sooner so you'll have to resleve it or get another cylinder. Hopefully both from the shop your working with.

Got a love it.

So Wiseco at one point did make a 90.25? I was questioning my shop's measurement, because I didn't see a 90.25 in Wiseco's lineup. The piston in it now, the 90.25, is definitely a Wiseco unless someone else made forged pistons at some point or my shop made a bad measurement. I will probably go ahead and confirm this with Wiseco anyway.

Can anyone confirm that Wiseco did in fact make a 90.25 at some point in their history? If so, how long ago did they stop making them? I emailed Wiseco, but the response did not confirm or deny that. They only said that they currently offer that piston in .5 increments.

post a photo dude.

k, they did, lets get this simplified

IF theres a # on the dome, post it, a 636 or 554 is a wiseco, if the number is 4 digits like 89.92 or something and has an arrow it probably a VERTEX, IF it has the name ART cast under it its probably stock or a rockey cycle, IF it says prox, its proX, If the piston has any machined look to the sides of it its a wiseco, measure the'rainbow shaped cuts width and post it either in mm or inches, if the ring is flat and not angled its a wiseco,

if you stil have trouble figuring out whats what, its you

The last time I looked you could get a Wisco in 89.25 and 89.75. The 89.75 is whats in my bike now. Its when you get to 90.00 that it jumps to 90.50 then 91.00. So there is no 90.25 or 90.75 unless perhaps one goes back several years. At that point its a moot issue and turns into to trivea question.

The numbers on top of the piston are "4987A". I do not see any other identifying marks. I am not sure how to post pictures on this site, and I don't have the time to figure it out right now.

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sounds like a vertex, no name cast underneath it?

Vertex says " Vertex" right on it....


The current Vertex in my bike is 5 years old....

http://cr500riders.com/cgi/yabb/YaBB.pl?num=1108665459


I'm putting a new one in next week.... I'll post up what a severly flogged, pinged, over-revved, and otherwise tourtured Vertex looks like.

ok, ya, i'm an idiot, i meant to say pro-x. Had jr helping me

Definitely not vertex. nothing is stamped on the piston skirt, and under the dome is smooth. It doesn't have that pattern in the picture.