Im confused.

[dxcody]

Ok, so when you bore out a 400ex, your boring out the cylinder sleeve right? NOT the cylinder?

Im working on a 400ex for my buddy. I have his stock KCY piston (he said he wanted me to rebuild it to stock) and a brand new 85 MM stock sleeve i bought off of ebay. Its from an actual store, not some guy out of his garage.

The piston doesnt fit in it. The cylinder obviously needs honed BUT honing it wont make the cylinder sleeve fit the piston. So do i take the sleeve to the machine shop and have it bored to fit the piston?

I was pretty sure it was the sleeve but i got to reading other posts and just got confused and wanted to clear this up.

It wouldnt make much sense to me to bore out the actual cylinder and then have to buy a sleeve to fit.

I know this is a dumb question sorry. I just want to be 100% sure.

[crownandmonster]

The sleeve gets bored for the piston, however in some cases the cylinder also needs bored to accept the sleeve.

[dxcody]

Originally posted by crownandmonster
The sleeve gets bored for the piston, however in some cases the cylinder also needs bored to accept the sleeve.

Ohh ok. That makes sense now and explains why i was confused.

I saw a post that said someone was getting their cylinder bored to match the sleeve.. and i was like what?

Thanks crown.

Does it make sense to you that the sleeve doesnt fit the piston?

Supposed to be an 85mm sleeve..

[powerbomb400]

I'd say that the sleeve would be a smaller diameter so that when they bore it to fit the piston they get the best fit possible. Gives the machinist room to work with. I watched my friend do a bore job on a cylinder and sleeve and he would check the fit and then take a little more out of the sleeve until it fits just right. You don't want the piston to hit the side of the sleeve. Only the rings.

geez good question.i never imagined the cylinder would have to be bored to fit the sleeve and the sleeve to fit the piston on direct stock replacements.it totally makes sense because no two anythings for the most part are identical,just never thought of it.good stuff.learn something new everyday.

[crownandmonster]

Originally posted by dxcody
Ohh ok. That makes sense now and explains why i was confused.

I saw a post that said someone was getting their cylinder bored to match the sleeve.. and i was like what?

Thanks crown.

Does it make sense to you that the sleeve doesnt fit the piston?

Supposed to be an 85mm sleeve..


The sleeve wont fit the piston. You have to have the sleeve bored to fit the piston, even though its an 85 mm sleeve and an 85 mm piston, there are to many variations between sleeve/ piston manufacturers to make a "one size fits all".


I have never had to put a sleeve in a 400ex jug, so I don't know if the cylinder needs bored to accept the sleeve. I have heard of people being able to heat up the jug and press the old sleeve out and the new one in but I'm not 100% sure.

I have put sleeves in 250r cylinders and they had to be bored to accept the new sleeve. I would take your whole set up to the machinist, he will know.

[CJM]

Buddy of mine took his sleeve and put it in another cylinder . Another buddy who does this sort of thing helped him. Heated up the cylinder and cooled the sleeve. Put the cyl on a few 2x4 and put the sleeve in there, plopped right in. Then he put it in the snow to cool it and voila done.

The piston will have to be matched to sleeve tho. Too many different slight tolerances for there to be a one size fits all.