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Sconnie
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1,745 Posts
Discussion Starter #1
So. my buddy ran into a problem with his sled and i'm not sure what caused it.

500 miles on a complete rebuild, new pistons, crank, seals, etc..

his jug just cracked. it's about a 5" crack near the base. I am just not sure what would cause that. seizing on the upstroke maybe? his pistons looked fine. The engine still runs, just very very crappy.
So thats problem #1. any advice on what would cause that? would it be anything to do with the crank?

2nd, we bought a used engine today. 50 bucks for a complete 500. The guy said "it was seized and now it's not." he really didn't know what he was talking about, he didn't know sleds or motors very well.

So we bought it, cause whats 50 bucks for a complete engine, it can be parted out for more than that.
Take the head off, and one piston has tons of piston wash. It's not cracked or broken. So, I'm thinking the reason it seized in the first place is either a bad crank bearing or somehow the coolant leak caused it to seize... this engine also has low miles on a fresh rebuild.

So, any advice on that issue? the goal is to make one working engine out of both of these.. both are stock bore, so pistons could be interchanged theoretically if needed.
 

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Premium Member
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34,103 Posts
Crack like that would allow coolant from the water jacket to seep into the base and ruin bearings. It would also cause over pressure in the cooling system. forcing coolant out of the overflow and overheating due to air locking.
Look for vertical scores on the cylinder walls and pistons (corner seize).
 

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Sconnie
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1,745 Posts
Discussion Starter #3
I'll check it out. How hard on the piston is that, would it be possible to use the better components of both these engines and make a good one? with new rings and hone
 

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Premium Member
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34,103 Posts
Water/coolant in the cylinder will cause the piston to melt as it makes the fuel burn hotter.
It will also cause detonation ( knocking) and can even cause a piston to crack.
 
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