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I picked up three pre-80 hondas in a barn find (400, 360, 350). The 350 and 360 are locked up.

After disassembly of the 350 I found the right cylinder frozen due to rust and the left with a hole in the piston and scoring on the wall. It appears that it had been recently rebuilt since there was no carbon at all in the left cylinder. I did find a rip in one of the diaphrams.

I've never rebuilt one of these 350s, does a non-functional diaphram cause one cylinder to run lean and fry the piston? I've had this happen before on 2-stroke jetskis where one cylinder drives the lean one causing the piston to fry. I'm thinking about putting Mikuni 32s on it to avoid it happening again.
 

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Sensei
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27,183 Posts
I guess it's possible, but a hole would usually indicate an obstruction or detonation in a 4-stroke.....Would have to see the actual hole to venture which.... Were the valves intact?
 

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A torn or swollen diapragm normally causes the slide not to lift, can't see that really being a lean condition bad enough to seize a piston. CV carbs are great if you take them time to rebuild them properly and use quality parts (I only use OEM). SCI kits are not that bad, not sure how they hold up over time. Once you get it running I'd check for air leaks around the intakes too. New manifolds are still available through honda, don't listen to what your dealer says. 32s seem pretty big for street use, I'd go with 30mm or even 28mm if you want a good idling bike.
 
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