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Author Topic: Black exhaust goo?  (Read 6698 times)

Offline frank mccune

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Black exhaust goo?
« on: October 13, 2016, 01:43:09 PM »
     Hi All:

     I was running my MVVS D7 today and the exhaust goo was jet black! I adjusted the needle valve and backed off the compression to where the engine was under compressed and missing.  No matter what I tried, the exhaust goo was sill very very black!  The engine started very easily and ran flawlessly.  Could it be bad fuel? Any suggestions?

                                                                                                    Tia,

                                                                                                    Frank McCune


Offline john e. holliday

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Re: Black exhaust goo?
« Reply #1 on: October 13, 2016, 08:26:42 PM »
What fuel mix are you using?  I know from experience that over compression will cause some black crud to come out, also old kerosene.  The kerosene should be clear like tap water.
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Online Russell Shaffer

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Re: Black exhaust goo?
« Reply #2 on: October 13, 2016, 10:28:51 PM »
If you are using a muffler, a loose one will make lots of black stuff from aluminum wearing.
Russell Shaffer
Klamath Falls, Oregon
Just North of the California border

Offline Motorman

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Re: Black exhaust goo?
« Reply #3 on: October 22, 2016, 11:34:54 AM »
If you are using ether from a spray can it has a top cylinder lube in it that burns at a very low temp and comes out black as coal even if your engine is rich and undercompressed with a light load prop. It's not a problem but your engine will coke up a little faster.


MM
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Online RknRusty

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Re: Black exhaust goo?
« Reply #4 on: October 22, 2016, 05:47:37 PM »
If you are using a muffler, a loose one will make lots of black stuff from aluminum wearing.
A rattling through-bolt in the muffler will do it too. So will one or more loose engine mounting bolts. Black exhaust goo is always alarming, but I hope it turns out to be something simple just vibrating.
DON'T PANIC!
Rusty Knowlton
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Offline frank mccune

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Re: Black exhaust goo?
« Reply #5 on: May 27, 2017, 09:55:08 AM »
     Hi All:

     I found the problem and corrected it.  The rear of the rod was rubbing on the crank disk.  I filed the rear of the rod for adequate clearance.  End of problem  The engine runs like a Diesel should.

      Thanks for all of the help!

                                                                                                                    Frank Mc cune


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