2004 yz 250 blown up

[yz supermoto]

HELP.. my 2004 YZ 250 has blown up, I have taken the cylinder off and the piston rings have broken, and the piston has cracked :-( . I have stripped it down and found that the cylinder has been bored out and sleeved and the cylinder is marked with the letter E.

I have measured the cylinder and the cylinder measures 66.35mm at the top and the centre measures 66.50mm and 66.40mm at the bottom.

What is the best meathod to repair, ideally not replacing the cylinder.

Are normal rings suitable for use with a sleeved cylinder.

Can I just put a replacement piston in?? What size??
Make??

Please help.

[PawPaw]

Originally Posted by yz supermoto

HELP.. my 2004 YZ 250 has blown up, I have taken the cylinder off and the piston rings have broken, and the piston has cracked :-( . I have stripped it down and found that the cylinder has been bored out and sleeved and the cylinder is marked with the letter E.

I have measured the cylinder and the cylinder measures 66.35mm at the top and the centre measures 66.50mm and 66.40mm at the bottom.

What is the best meathod to repair, ideally not replacing the cylinder.

Are normal rings suitable for use with a sleeved cylinder.

Can I just put a replacement piston in?? What size??
Make??

Please help.

You need to get away from the sleeved cylinder. You need to get back to a stock set up for better life. It also will make getting parts an easier task.
It will cost more initially, but you will be much better off.

Paw Paw

[arnego2]

Sorry to hear that,

at best get in touch with millenium plating, uschrome, powerseal and look what they have to say. Those companies do jug repairs. Good luck anyhow you are looking at splitting the engine and doing bottom end together with top. Those parts falling into the crank don't mean any good.

[bronc3]

I have had great luck with Millennium, zero problems.

[351mustanger]

I don't think millennium or the others can bring a sleeved cylinder back to the stock plated condition. With some searching you could get a damaged but repairable cylinder for next to nothing and have it repaired by above mentioned companies or you could find a good price on a new one. I would not try to buy a "good condition" used one. What somene else considers "good condition" will most likely not meet your expectations. I bought a new cylinder on ebay a few years ago for an '02 yz250 for $285. You can expect to pay about $240 to get one repaired (with all the shipping included). Not to be the bearer of bad news but, you will be in the $600 range at least, to bring it back to life (in stock form). You could bore the sleeve and go oversized for less money but it wont last nearly as long. A bottom end rebuild is mandatory with shattering piston and rings. The bottom end will most likely fail, if left unattended, because of all the pieces of metal introduced to the bearings.

[yz supermoto]

only problem is I'am in the UK and can't find a cylinder for this year??? only older ones...

was hoping that a re bore of the sleeve & over sized piston would be sufficiant but don't want to waste money rebuilding if sleeves are no good

Also was hoping not to have to split bottom end as when I stripped it the broken bit of ring was saved from falling into bottom by using a magnet.

I will try and find a new cylinder from Yamaha if possible but is their any quality non genuine cylinders made??

Thanks for your advice so far.

[arnego2]

If correct USchrome works with [Only registered and activated users can see links. ] which are from the UK try to contact them, IMO replate beats a new cylinder anyway.

[351mustanger]

You may or may not be ok doing the bottom end. I would not gamble the money spent on the top end though. I was in this same position with my own bike. At first I was thinking the same thing, but I did the bottom end also. I'm glad I did. I used a wiseco crank kit (about $200 and comes with all the gaskets and seals for the bottom end. Also comes with main bearings and the top end bearing). Some will tell you the wiseco kits are not any good. I have had mine in a yz250 for the last three years with no problems. I even "abuse" it with a 50:1 pre-mix. I had just bought my bike when the damage happened, so it was not in my budget for this. I bought the bottom end kit first and removed the engine and worked through it while saving money and looking for deals on the top-end parts I needed. That is what I would suggest to you.