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honda 250r
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Posted by: kruzofman

well dudes, i am finally starting to put my 250r tegether, and right now iam rebuilding the engine, and was wonder how should i go about honing the cylinder? i well be getting the pistion soon, i also wanted to know how tight shounld the pistion and rings be when i put the cylinder on....but other then the rebuild i am getting closer to having the R back....

Posted by: seth400

spec clearance is .0025- .0030 i think i would give it more near .0030 or it will take u forever to break the top end in. at least thats what the guy who did my clyinder told me.

Posted by: JTRtrx250r

Does it need a hone, or a bore? You can break the glaze w/ some 400-600 sandpaper very lightly, but if its bored...dont forget to champher the ports, and releive the exhaust bridge 0.006

Posted by: kruzofman

also how much wounld it cost to buy a hone tool? and wounld using sand paper to sand down the edges on the ports be alright or is there a better way? thanks...

Posted by: Rich250RRacer

quote:
Originally posted by kruzofman
well dudes, i am finally starting to put my 250r tegether, and right now iam rebuilding the engine, and was wonder how should i go about honing the cylinder? i well be getting the pistion soon, i also wanted to know how tight shounld the pistion and rings be when i put the cylinder on....but other then the rebuild i am getting closer to having the R back....

Maximun allowed clearance is .006, but with this much you tend to get piston slap. If you have this much but dont want to bore it,
go with a Pro-X or stock Honda piston, as they tend to be more uniform is size from top to bottom. Wiseco pistons are great but they do taper from top to bottom.

Posted by: JTRtrx250r

I should have said 0.004-0.006, I run Wiseco's and 0.006 at the bridge for expansion , the 3 oil lube holes are 100% nesscessary and I dont get piston slap, maybe w/ an old past-due top-end you might..

Posted by: Rich250RRacer

.006 at the bridge is fine, since this is one of the hottest spots on the cylinder, but this is not where the clearance is measured. If you've got .006 or more at the bottom of the cylinder, or anywhere else in the bore, except on the bridge, you are likely to get slap, even with a FRESH top end. I also run Wiseco, even though they have the taper, and usually will run up until I get .006 or a little more before I bore. At .005-.0055 is the point where slap starts to become noticeable.

Posted by: JTRtrx250r

quote:
Originally posted by kruzofman
also how much wounld it cost to buy a hone tool? and wounld using sand paper to sand down the edges on the ports be alright or is there a better way? thanks...

You can buy honing tools, and use WD-40

for the champhering most shops use angled die-grinders, Ive seen a guy use a small flat-file and a small round-file, you just dont want the sharp edges to scrape the lube off and scratch the piston , resulting in a smoked top-end, I ve never had 1...even racing at 1200 degrees on the EGT, proper set-up is everything and releiving the exhaust bridge on a Honda is 100% necessary

Posted by: honda racer 211

what do you mean releiving the exhaust bridge I have never done that. do i need to

Posted by: JTRtrx250r

Yes(after the bore), it gets the hottest b/c its the exhaust port, the heat causes it to expand and that little bridge in the exaust port helps take the load on that side, a reputable shop does this w/o being asked(along w/ champhering the ports), but Ive seen a few that just bore and hone and send it out the door, you can do this yourself if thats what you have in mind, Wiseco sends the assembly directions in the box w/ the piston. You'll get a piston, rings, circlips,wrist-pin and directions in the kit...but you'll have to buy the pin bearing seperate tho