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I need a replacement piston. 871M08900 is standard. My cylinder feels OK with some visible scuffing. If the standard size is meant to have the cylinder honed out .001 for the forged type piston, then I can probably use just the standard piston. If it is made to work with the standard stock cylinder clearance then maybe I need to go 1 over. Can anyone clarify if the standard size forged piston is meant to have ~.001 more honed out of the standard 89mm bore? Or is it meant to drop in to the stock cylinder with no additional clearance?

I have my cylinder pulled and the 'feeler' gauge piston clearance is about .010. If I know what I'm hearing I could hear some pretty load knocking when it was warmed up. Crank and rod bearings and wrist pin look and feel very good.

Thanks.

I called Wiseco and they say the std size piston is appropriately undersized for the stock cylinder bore size, so no additional material removal is desired, except honing.

Hit up blownbillybob, every piston will vary a little....I guess you could just slap something together but for a motor that will last years and years I'd just do it right. Send the jug to Bill, he will size it properly with the proper bore measuring equipment that will make sure it isn't tapered or any of that and can let you know what size to order after it smooths out the scoring. You have the piston drop shipped to bill and he will do the final sizing to THAT piston. When you get all your parts back if you have the gasket kit ready to go it will take you a few minutes to slap it all together and if it's a trail bike the top end will last for years....like 10.

Rhino89523 wrote: ↑January 14th, 2020, 9:51 am Hit up blownbillybob, every piston will vary a little....I guess you could just slap something together but for a motor that will last years and years I'd just do it right. Send the jug to Bill, he will size it properly with the proper bore measuring equipment that will make sure it isn't tapered or any of that and can let you know what size to order after it smooths out the scoring. You have the piston drop shipped to bill and he will do the final sizing to THAT piston. When you get all your parts back if you have the gasket kit ready to go it will take you a few minutes to slap it all together and if it's a trail bike the top end will last for years....like 10.

This guy knows a thing or two about these bikes... I would listen to his advice.

There's a guy named John Tice, http://www.smallenginemachineworks.com, who has been very active in cylinder re-boring who lives just about 30 miles from me. So far he seems like the best local option. What experience has anyone had with his services?

I sent a PM to blownbillybob but have received no reply yet. Does anyone have a business name or phone I could use to contact? Thanks.