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

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.

If you are using a muffler, a loose one will make lots of black stuff from aluminum wearing.

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

Quote from: Russell Shaffer on October 13, 2016, 09:28:51 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.

     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