69mm bore and 69mm piston

[fatty_k]

I plan on getting my cylinder re-plated and installing a new Wiseco piston kit (standard 69mm). Im just wondering how this is going to work? Shouldn't the bore be bigger or the piston smaller? Then the rings just take up the extra space, and allow for heat expansion?
Thanks.

 

[jdbrusch]

The shop that does the plating will usually require the piston that is going to be used in it before they do the plating and final honing.The piston is yes considered 69mm but it is slightly smaller then this,the clearance between the piston and cylinder is about .072-.092mm,this is less than the thickness of a hair.Say your piston measures in at 68.900 the shop will final hone the bore to 68.972 mm to give the very minimum in clearance,but the manufacturer of the piston may have some different specifications usually they are included with the piston kit.

 

[canyncarvr]

Repeat for emphasis...IF whoever does your boring/plating does NOT want the piston that's going in the bike, find someone else to do the work!

There is no reason to approach the fit from a 'one size fits all' point of view. You aren't trying to put together a bike for every man, but YOUR bike with YOUR parts.

That's one thing that's nice about pro-x and the 200 piston choices they supply. Unfortunately, that point doesn't apply to you.....

Rings aren't there to 'take up space' btw. Piston to cylinder fit is critical ..especially in a 2-smoke. Somehow figuring to substitute a ring fit for a piston NON-fit is a non-sequitur....an oxymoron.

Who's doing the plating? Consider langcourt as a possiblity. I haven't dealt with them personally.....just aware they are a choice.

http://www.langcourt.com/

And they're even in canada!!! In BC even!!!

Cheers!

 

[fatty_k]

I think I am going to go with http://www.mongoosemachine.com/. They are located near Langcourt actually. They are also a Yamaha affiliate and since I work at a Yamaha shop, I can get re-plating done relativley cheaply. I will make sure to send them the Wiseco piston I will be installing.
Thanks.

 

[jdbrusch]

I've had a few cylinders done by Jay down at Mongoose(they are associated with Langcourt) they do really nice work.If you do not have a piston already give him a call,they are actually a Wiseco distributor and may give you a deal.Really fast turn around,I sent my cylinder from my WR250f in for a big bore 280 kit,they got it on tuesday and I picked it up on friday afternoon. :thumb:

 

[fatty_k]

I actually got my Wiseco piston kit from Mongoose. ;)