port,polish, & piston size and brand

[eddie1]

port,polish, & piston size and brand pictures

ok just took off the entire top end off my 1990rm250

inspected it and the left side of the piston is totaly blownout the rings r flush with the head n the hole side of the head is scratched n has groves init along with the left side of the engine head.

if im correct i need to get the head ported and polished and it will be smooth an uniform again? if not what then?

and once this is done will a standard 67mm piston fit or do i have to buy a oversized one 0.20, 0.40 ect?

and what brand of piston would you guys recommend for the longest life? life over performance.

Also there is no sleeve in the head that slides out or nothing is this normal?

also and pointers or tips in rewbuilding an engine correctly n rightly?

any help is great this is my first engine rebuild.

Eddie

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[snb73]

Hard to tell by the pictures but it looks like you're ready for a replate. You will need to measure the bore to be sure. If you can catch your fingernail on the scratch, that is a good indicater too.

http://www.eric-gorr.com

http://www.uschrome.com/cylinder_repair.html

 

[eddie1]

is that the same as port and polish i have a buddy who own a hsow n will port n polish for free

 

[eddie1]

???

 

[MOTO ON RM250]

well im no expert but i know for sure that porting/polishing is definetly not the same as replating. i think replating is when they put a new sleeve in to get it back to standard bore size. porting/polishing is when they use some sort of dremel and smooth out the intake and exhaust ports

 

[Ol'89r]

if im correct i need to get the head ported and polished and it will be smooth an uniform again? if not what then?

and what brand of piston would you guys recommend for the longest life? life over performance.

Also there is no sleeve in the head that slides out or nothing is this normal?

]

Porting and polishing has nothing to do with your head. It refers to the ports in the cylinder being modified.

You need to send your cylinder to Eric Gorr and have it replated. He will repair the scratches and replate the bore and it will be like brand new. He can also provide you with the correct piston. Use the link smb73 provided to contact him.

You can re-sleeve the cylinder with a cast iron sleeve but, you will lose performance. It's best to replate your cylinder back to stock.

You should be able to get an OEM piston from your dealer or use a Wisco or Pro-x. All good pistons.

From looking at your piston, you may want to consider taking the whole engine apart. You probably have pieces of metal from your piston and rings down in the crankshaft area. If you put the bike back together without cleaning that out, your crank bearings could go bad.

When your done, be sure to jet your bike properly and make sure you run a good quality two-stroke oil at the right mixture.

Beware of friends that offer to port and polish your cylinder for free. If they knew what they were doing, they wouldn't be doing it for free. :cool:

 

[RedBull]

I would recomend LAsleeve with a wisco pistion. you MIGHT be able to hone your bore but I doubt it. when you resleeve you can keep your original bore size so you dont have to worry about a special order piston. I have never used LaSleeve personaly but have heard good things heres a link for all you need http://www.lasleeve.cc/index.cfm?year=1990

 

[griffbones]

I would recomend LAsleeve with a wisco pistion. you MIGHT be able to hone your bore but I doubt it. when you resleeve you can keep your original bore size so you dont have to worry about a special order piston. I have never used LaSleeve personaly but have heard good things heres a link for all you need http://www.lasleeve.cc/index.cfm?year=1990

By sending the cylinder to Eric or directly to US Chrome, you should be able to retain the stock bore size and use an OEM piston or aftermarket which ever you choose. To me replating is a much better option than sleaving a cylinder. IMHO

 

[RedBull]

Survey SAYS..... griffbones is right

http://www.dirtrider.net/forums3/showthread.php?t=149501&highlight=replating

 

[cujet]

Replate, it is simply the best option.

If, for some reason, you choose to use a cast iron sleeve, remember that they wear about 10 times more quickly, but you can bore them out oversized, assuming an oversized piston is available when you need it. And you will need it! Also, the cast iron sleeves do not transfer heat as rapidly as a Nikasil plated cylinder. This can cause issues not common to the original, plated design.

Chris

 

[BigRedAF]

Send it to Eric Gorr or Rick Peterson for a re-plate. No offense about your friend but grinding on your ports without knowledge is the fastest way to trash your engine.

LA Sleeve won't be as nice as a re-plate and will require port matching to align the sleeve.

The pics are your cylinder, hows the head, any dings in it? If so Eric can deck it and re-cut the chamber to proper size and shape when he does the cylinder work.

What caused the damage in the first place, dirt, dry side seal air leak? If so send your whole engine and have the crank and big end rod bearings replaced too.

 

[eddie1]

he guy i bought it from hade that same piston in it for 2 yrs and i was just coming home from riding n the engine died.

head is fine

im sending it ot the guy u guy r recommending, my buddies sending his engine for his camero in so he said he'd ship my head with his engine, so i guess that workd out ok

thanks for the help, let u guys know how it goes once it comes back to me