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View Full Version : rebuilt head using original piston?



ryanh250ex
05-23-2006, 01:32 AM
OK, so i have a bit of a dilemma on my hands.

my 250ex has 100-110 hrs of use on it. i've always taken good care of it, but realistically, i've ridden the snot out of it.

lately i've been noticing some smoke on start up, when you rev it up, it will smoke on deceleration. i personally thought it was kinda weird. I figured maybe valve seals.

I had a buddy start going through the gears on it, and while the bike was not warm (it had only been running for maybe 2-3 minutes), as he was going from 1/4 slowly to full throttle, i did notice a very small amount of blue-tinted smoke come from the tailpipe. it quickly dissipated into nothing, and went away once the bike had warmed up a bit.

I'm suspecting that the valve guides and seals are letting oil through. So, i was thinking about eventually doing a rebuild. However.....

I'm a college student now, and riding is really not nearly as important as it used to be. I still love riding as much as when i first threw a leg over a bike, but as i've gotten older, i have more responsibilities, and the simple fact is that it's a hobby, nothing more, nothing less.That said, i dont want to spend an insane amount of money on a rebuild on a bike i am not even home to ride all that much.

So, since the 250 runs GREAT- starts up first crank every time, pulls hard through every gear, i can yank power wheelies in 3rd- but seems to have a problem with puffing smoke on cold engine deceleration, can i do a rebuild on the head, and mate it to the original piston?

also, what should i expect to pay for a decent head rebuild?

ohsobad_chevy
05-23-2006, 08:35 AM
I would definately not put the piston back into a newly honed head. You will need to get a new one (about 100 bucks) but worth it. If you have your head honed you are lookin at about 75 bucks or so. Strongly suggest that you get a new piston.

ryanh250ex
05-23-2006, 11:27 AM
Originally posted by ohsobad_chevy
I would definately not put the piston back into a newly honed head. You will need to get a new one (about 100 bucks) but worth it. If you have your head honed you are lookin at about 75 bucks or so. Strongly suggest that you get a new piston.

i'm talking about the head, not the sleeve/cylinder.

is their any honing involved with the head? i.e. with lapping the valves, cleaning up all the carbon and crap, etc. i always thought that everything was cleaned up via porting/polishing. and then of course new valve guides, etc etc.

ohsobad_chevy
05-23-2006, 01:40 PM
You asked whether you should keep the same piston, right?? I said that you should not, esp with 100 or so hours on it... I definately think that you should get the head re-worked, but I was answering the question: Should i mate it to the same piston? The smoke could be leaking valve seals as well as oil getting past your rings since there is 100 hours on it. I simply said that if you get your head re-worked, get your cylinder honed and get a new piston, rather than putting the same one back in it. It is only an additional $75 (at most) to get it honed.

Chino886
05-23-2006, 01:56 PM
Originally posted by ohsobad_chevy
I would definately not put the piston back into a newly honed head. You will need to get a new one (about 100 bucks) but worth it. If you have your head honed you are lookin at about 75 bucks or so. Strongly suggest that you get a new piston.

I think he could use the stock piston....BUT, you would have to use new rings and circlips. ALSO, make sure you do not have any play in the wrist pin.

My 2 pesos!! :devil:

ohsobad_chevy
05-23-2006, 02:11 PM
I agree that he could use the original piston, but it would be a real good idea to hone the cylinder while your inside the engine, and put in a new piston.

Chino886
05-23-2006, 02:14 PM
Originally posted by ohsobad_chevy
I agree that he could use the original piston, but it would be a real good idea to hone the cylinder while your inside the engine, and put in a new piston.

Yeah, if he is on a budget, I would hone it, get new rings, circlips, and reassemble.

But if it were me, I would bore it, P & P, valve job, cam, rod.......(it keeps going, and going, and, going.......) :muscle: :muscle: :muscle:

:muscle: :muscle: :muscle: