Again, doesn't that piston dome look awfully high, especially for a 750 (which gets almost a full point more CR just from the added displacement)?
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77 shell 750CC holed the piston
- Thread starter KcKeeny
- Start date
What gas was being used? Detonation is um rather loud?
AUTOMAN
XS650 Addict
Methylcyclopentadienyl manganese tricarbonyl
Used in the '80-'90's by all major brands.
Until it was found that it clogged up cats and contaminated water tables.
Octane booster.
Banned in Canada/US years ago.
China in 2010.
cliff
Used in the '80-'90's by all major brands.
Until it was found that it clogged up cats and contaminated water tables.
Octane booster.
Banned in Canada/US years ago.
China in 2010.
cliff
This question also supports the valve theory more than detination.
I was using 98 pump gas. Should have been running 107 leaded?
We don't know the compression ratio so can't really say. A quick bandaid for motors too strong for street gas is to retard the timing. Don't spose you got a compression reading? I've run an XS650 that pulls 190PSI (that gauge reads 150 on healthy stock motors) on street premium. Shrug.
Maybe try to identify the pistons? Surely, there aren't that many potential brands that were used back whenever the engine was built?
To say if it's pre ignition or not you would need to see both pistons so you can see the state of the other one,
What pistons are they if they are JE these are very strong and will take being touched by the valve, I've had a few valves touching the piston,
You might want to examine the crank to see if this has spread and caused the piston to go in an odd way as its not a hole to speak of the top of the piston is missing on the exhaust side, if it was ignition I would expect it to blow a small hole in the piston where yours looks like it's almost ripped the top off of it, unless there's no oil in the engine, but you can see oil on it so I doubt that
What pistons are they if they are JE these are very strong and will take being touched by the valve, I've had a few valves touching the piston,
You might want to examine the crank to see if this has spread and caused the piston to go in an odd way as its not a hole to speak of the top of the piston is missing on the exhaust side, if it was ignition I would expect it to blow a small hole in the piston where yours looks like it's almost ripped the top off of it, unless there's no oil in the engine, but you can see oil on it so I doubt that
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Funny, op asked why but doesn't seem to b listening to all who ask for pics of the other piston to help define an answer.
Funny, op asked why but doesn't seem to b listening to all who ask for pics of the other piston to help define an answer.
AUTOMAN
XS650 Addict
Underside of pistons may tell us something, I rest on my experience.
Skull, you are correct on the replies. Experts here to help and lack of feedback is typical for any websites.
cliff
Skull, you are correct on the replies. Experts here to help and lack of feedback is typical for any websites.
cliff
Part of the reason don't comment a lot these days. Especially when i see the op is not engaged...........why waste my time giving to someone who doesn't seem to be interested
