HarleyTechTalk

Technical Forums => Milwaukee-Eight => Topic started by: rich1 on June 26, 2020, 07:20:12 AM

Title: Is this amount of carbon normal?
Post by: rich1 on June 26, 2020, 07:20:12 AM
Stock 114 M8. Normal for an M8?

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Title: Re: Is this amount of carbon normal?
Post by: 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.
Title: Re: Is this amount of carbon normal?
Post by: rich1 on June 26, 2020, 09:01:22 AM
Thanks
Title: Re: Is this amount of carbon normal?
Post by: TXChop on June 26, 2020, 12:10:04 PM
For an M8...yes.
Title: Re: Is this amount of carbon normal?
Post by: Ohio HD on June 26, 2020, 01:13:32 PM
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?
Title: Re: Is this amount of carbon normal?
Post by: rigidthumper 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.
Title: Re: Is this amount of carbon normal?
Post by: 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?
Title: Re: Is this amount of carbon normal?
Post by: rich1 on June 28, 2020, 05:21:31 AM
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.
Title: Re: Is this amount of carbon normal?
Post by: Hossamania on June 28, 2020, 06:11:01 AM
Re-route those breathers away from the intake.
Title: Re: Is this amount of carbon normal?
Post by: rich1 on June 28, 2020, 06:18:04 AM
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
Title: Re: Is this amount of carbon normal?
Post by: RTMike on June 28, 2020, 06:32:17 AM
Blow by as in combustion pressure leaking past the rings.
Title: Re: Is this amount of carbon normal?
Post by: rich1 on June 28, 2020, 08:24:52 AM
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.
Title: Re: Is this amount of carbon normal?
Post by: 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. 

(https://i.imgur.com/Xbgm5WD.jpg)

Title: Re: Is this amount of carbon normal?
Post by: rich1 on June 30, 2020, 01:49:58 AM
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. 

(https://i.imgur.com/Xbgm5WD.jpg)

Good info. Thanks
Title: Re: Is this amount of carbon normal?
Post by: Hillside Motorcycle on June 30, 2020, 04:19:11 AM
Normal from what we've witnessed.