new to forum 04 cr125r rebuild

[killer454]

hello everybody as you can see im new to the forum,and im glad they finally activated my membership.my nephew has traded a 2006 yamaha blaster for a 04 cr125r.the bike would not stay running when we went to do the trade so i said to my nephew are you willing to put 300 in the bike.he said yes so we left with it.

here is what the bike does;
*bought 5 plugs and it has fouled everyone of them
*wont start and if it does it just boggsout
*if i get it started it will run good reved full throtle but when back to mid bogg and try to die.
*i did a compression test and it looks like around 60lbs,so this is low should be around 160.
*so im tering it down now

heres what i found when i took topend off:
*carb has been cleaned by me all stock setting and jets in this bike.
*i removed the reed cage and they are fine cant see light through them at all no cracks good on these.
*while the reed cage was out i took my hand and pushed the kicker down and can hear compression leaking through the rings.
*removed head and it is so clean i can eat off it (no carbone)looks like sombody cleaned it.
*removed cylinder and piston and they looked real good to no gaulding or major damage at all.plating looks pretty good,piston skirts look very good.
*i took the old piston ring out and put it in the cylinder and checked the endgap on it.manual said max gap is .026 and i measured around .030 so ring is woreout for sure.
*rod and crank are fine
*took the cylinder to the local kawasaki dealership to have the cylinder miced.and he says it out of round by 2.5 thousands.

this is where im at on this thing right now,and could use some advice.my nephew is not going to race this bike just trail ride mostly and may hit a few jumps on the track once in awhile.

i found a guy that will put a sleave in the cylinder for 300 and it will have 3 or 4 bores after stb bore.im thinking this is the way to go since hes not racing it.if it gets messedup again just bore and go.i have researched on this forum and called to price the replating and it is going to run 200 just for the plating.the sleave guy is going to sleave it and supply namara piston kit with gaskets for 300 even.

can you guys give me some advice please this is the first bike i have messed with.i have rebuilt 400exs and blasters so i know some things.and im a great car and truck engine rebuilder.not bragging just letting you guys know my hands on experiance.

thanks killer454 :nod:

 

[2strokerfun]

Either way will be fine if done by a competent professional. I'm old-school and like iron sleeves. But I'm in a tiny minority. Most prefer replating. As you've probably researched, you get better heat transfer and more even expansion of piston/cylinder with replating. Done right, they can last years in mild trail riding with proper maintenance. Downside is you can't easily overbore and grenading a piston or a ring usually means another replating. With sleeve, you bore up .5mm, hone and throw in a new slug and rings. But it is easier to have a cold seizure with sleeve as sleeve expands less rapidly than piston during warm-up; heat transfer isn't as efficient; and ports on sleeve are often less than optminally matched up to cylinder. Done properly, either is fine. The key is really about the craftsmanship of the work being done. Finding the cheapest route isn't always the best. Having said that, I'm a Wiseco piston guy and I'd drop the extra cash for one, either way. No experience with namara, good or bad.

 

[killer454]

well thanks for the advice,i have decided to go with the sleeve sent it off yesterday.i should have the cylinder back in a couple of weeks.

i will take pictures of the finished cylinder when i get it back and post pictures on this thread.

im going to try the sleeve dont know how well it will be but what the heck.i must go with my gut feeling,if it turns out to be wrong after going with the sleave i will buy a new 300 cylinder.

right now im replacing crank seals and installing a new clutch!

 

[whenfoxforks-ruled]

I would have replated and put a Wiseco top end in. And a new bottom end also. Putting a sleeve in a 125, the worst thing possible. It will run hotter, be harder to jet, and have a shorter ring life, on top of a cheaper piston. Vintage Bob