Rebuild Questions

[corypro]

So as you may know, I'm doing a complete rebuild on my 350 and this will be my first teardown on a 2 stroke. The mechanic in me keeps wanting to going back to reference past jobs on my engines (in my head), but I know I shouldn't be doing this so hopefully you guys can guide me in the right direction.

 

First things first. I've read the Clymers manual and the downloadable service book and followed every step. So far it's been rather simple and I haven't hit any snags yet, but I know I will when it comes to the technical stuff, so here I go.

 

I pulled the heads off and measured the dimension with a caliper and they were both 62mm across. Stock dimensions in my manual say it's 64mm? Can someone confirm this?

 

Second question, can I replace the 62mm pistons with the same size or no? If no, I'm assuming I will have to hone it out to the next size up. Will I require a 62mm piston with oversized rings or a larger piston with normal rings? If yes, what should I keep an eye out for? I would imagine there has been some warpage and the pistons may have some play in the cylinder. It also looks like the walls on one cylinder head have been scored,

 

Third question. The cylinder head plate/dome has some damage

 

Can i use a dremel to debarb the grooves and flatten it out or will this cause air flow issues or possibly lean out my a/f? I would image not since the surface area increase would be marginal.

 

Fourth question. The conrod can move freely on the crank due to the blown out bearing. When I pull the crank out of the case, what other internals should I replace while I'm in there? If the crank is scored where the conrod sits, what steps should I take (if any) to fix this?

 

Fifth and last question (for now). This is one I'm having troubles with and have no clue where to go. What head gasket would you recommend? Oversized? Regular? Cosmetic? Also, can someone shed some light on these for me? How do each differ? Performance? Durability? Strength?

 

Thanks once again guys for helping me out. I truly appreciate it!

[Larry's Shee]

Stock bore 64mm. Calipers are not the best tool for inside dia. , Inside micrometer is best because you also need to measure several different places down bore.If you need a new piston your bore would have to be within service limits or less to just drop a new piston in. I.E. out of round and taper, plus you would have to use exact same style of piston. Would be far better off boreing to next oversize and start with totally fresh engine. Head would have to be remachined, replaced w/ stock, or get cool head. Crank will cost as much or more to be rebuilt as to buy new, make sure you get one that's already welded. New crank seals. Upgrade water pump if funds allow. JMHO , your results may vary.

Edited October 5, 2010 by Larry's Shee

[corypro]

So I looked into a larger bore and it seems there are pistons available in increments of .25mm. If I'm going to bore it out, what size would you deem acceptable before I would have to go with bigger jets or more a/m parts? I wouldn't mind going a bit bigger if I have to replace the internals anways.

 

Any suggestions would be greatly appreciated.

[Larry's Shee]

Only bore what is needed to clean it up. You would have a hard time measuring the HP between a 64 and a 64.25 bore . Even if you bored to max might not see a difference. No jetting change needed.