Detonation

[TimothyJones]

Hi All,

While checking head clearance ( around .008") on one of my cmb 45 gold head motors I noticed and what looked to be a sandblasted effect/pitting on top of the piston at the exhaust side.

The motor has ran well for years using same 50% fuel, plugs and never ran lean always slightly rich and so forth.

Is this detonation, pre-detonation? and if so what the best fix. Mostly running in 75 deg weather.

Thanks In Advanced

Tim

 

[Joe Warren]

Hi All,

While checking head clearance ( around .008") on one of my cmb 45 gold head motors I noticed and what looked to be a sandblasted effect/pitting on top of the piston at the exhaust side.

The motor has ran well for years using same 50% fuel, plugs and never ran lean always slightly rich and so forth.

Is this detonation, pre-detonation? and if so what the best fix. Mostly running in 75 deg weather.

Thanks In Advanced

Tim

In stall new brgs and try again. If it contuines add .002 head clearence. any slight change in fuel or mfgers & altitude will also cause this

 

[TimothyJones]

Thanks Joe and others who have contacted me.

Yes I will raise .002"
Its was a preexisting condition and bearings are good to go.

I think I'm on the right track,reading up on this and understanding it better.

Stu has also given some pointers

I will let you know on the kits Monday, Did not come in the mail Yesterday.

Thanks

Tim

Hi All,

While checking head clearance ( around .008") on one of my cmb 45 gold head motors I noticed and what looked to be a sandblasted effect/pitting on top of the piston at the exhaust side.

The motor has ran well for years using same 50% fuel, plugs and never ran lean always slightly rich and so forth.

Is this detonation, pre-detonation? and if so what the best fix. Mostly running in 75 deg weather.

Thanks In Advanced

Tim

In stall new brgs and try again. If it contuines add .002 head clearence. any slight change in fuel or mfgers & altitude will also cause this