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Is this amount of carbon normal?

Started by rich1, June 26, 2020, 07:20:12 AM

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rich1

June 26, 2020, 07:20:12 AM Last Edit: June 26, 2020, 03:51:01 PM by FSG
Stock 114 M8. Normal for an M8?

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rigidthumper

Not uncommon. A little oil comes past the rings, a little comes from crankcase breathers,  and the rest from combustion of fuel that comes from oil.
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TXChop


Ohio HD

Quote from: rigidthumper on June 26, 2020, 08:58:59 AM
Not uncommon. A little oil comes past the rings, a little comes from crankcase breathers,  and the rest from combustion of fuel that comes from oil.

Robin, do you think that the thick OEM head gasket is contributing to that?

rigidthumper

Hard to say. I do believe wide quench areas lead to less efficient combustion, but I believe that a lot of the carbon found on tops of pistons is from less than perfect ring sealing.
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

Pirsch Fire Wagon

I've not seen them with that amount of Carbon. What's the Mileage?
Tom

rich1

Quote from: Pirsch Fire Wagon on June 27, 2020, 06:38:32 AM
I've not seen them with that amount of Carbon. What's the Mileage?

8K miles. Bike does have more oil mist via the breathers than I ever saw in any TC. Both cylinders passed leak down test. So maybe these M8 bikes breather system doesn't work as well as the TC.

Hossamania

Re-route those breathers away from the intake.
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it can take away everything you have.

rich1

Quote from: Hossamania on June 28, 2020, 06:11:01 AM
Re-route those breathers away from the intake.

Already done. But some carbon had already formed

RTMike

Blow by as in combustion pressure leaking past the rings.

rich1

Quote from: RTMike on June 28, 2020, 06:32:17 AM
Blow by as in combustion pressure leaking past the rings.

That could be. Leak down test numbers were really good. But with engine running the pressures are higher. Those are some big pistons going up and down.

Thermodyne

Take the air filter off and see if there is oil that has collected in the recess in the opening of the throttle body.  It almost looks like the recess was intended to catch oil dripping from the breather hoses.   About half the ones I've looked at have oil puddled there.

The oil on the piston above looks like carry over to me. 

When the rings loose oil control, there will be a wet margin around the edge of the piston with a dryer looking center. 




rich1

Quote from: Thermodyne on June 29, 2020, 11:08:12 AM
Take the air filter off and see if there is oil that has collected in the recess in the opening of the throttle body.  It almost looks like the recess was intended to catch oil dripping from the breather hoses.   About half the ones I've looked at have oil puddled there.

The oil on the piston above looks like carry over to me. 

When the rings loose oil control, there will be a wet margin around the edge of the piston with a dryer looking center. 



Good info. Thanks

Hillside Motorcycle

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