Author Topic: Is this amount of carbon normal?  (Read 699 times)

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Offline rich1

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Is this amount of carbon normal?
« on: June 26, 2020, 07:20:12 AM »
Stock 114 M8. Normal for an M8?

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« Last Edit: June 26, 2020, 03:51:01 PM by FSG »

Offline rigidthumper

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Re: Is this amount of carbon normal?
« Reply #1 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.
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Offline rich1

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Re: Is this amount of carbon normal?
« Reply #2 on: June 26, 2020, 09:01:22 AM »
Thanks

Offline TXChop

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Re: Is this amount of carbon normal?
« Reply #3 on: June 26, 2020, 12:10:04 PM »
For an M8...yes.

Offline Ohio HD

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Re: Is this amount of carbon normal?
« Reply #4 on: June 26, 2020, 01:13:32 PM »
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?
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Offline rigidthumper

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Re: Is this amount of carbon normal?
« Reply #5 on: June 27, 2020, 06:31:35 AM »
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.
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Offline Pirsch Fire Wagon

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Re: Is this amount of carbon normal?
« Reply #6 on: June 27, 2020, 06:38:32 AM »
I've not seen them with that amount of Carbon. What's the Mileage?
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Offline rich1

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Re: Is this amount of carbon normal?
« Reply #7 on: June 28, 2020, 05:21:31 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.

Offline Hossamania

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Re: Is this amount of carbon normal?
« Reply #8 on: June 28, 2020, 06:11:01 AM »
Re-route those breathers away from the intake.
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Offline rich1

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Re: Is this amount of carbon normal?
« Reply #9 on: June 28, 2020, 06:18:04 AM »
Re-route those breathers away from the intake.

Already done. But some carbon had already formed

Offline RTMike

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Re: Is this amount of carbon normal?
« Reply #10 on: June 28, 2020, 06:32:17 AM »
Blow by as in combustion pressure leaking past the rings.

Offline rich1

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Re: Is this amount of carbon normal?
« Reply #11 on: June 28, 2020, 08:24:52 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.

Offline Thermodyne

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Re: Is this amount of carbon normal?
« Reply #12 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. 




Offline rich1

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Re: Is this amount of carbon normal?
« Reply #13 on: June 30, 2020, 01:49:58 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

Offline Hillside Motorcycle

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Re: Is this amount of carbon normal?
« Reply #14 on: June 30, 2020, 04:19:11 AM »
Normal from what we've witnessed.
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