What's causing this?

Old forum posts ending on Oct 21 '09

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Twin Pinzies
Posts: 545
Joined: Mon Jan 03, 2005 1:33 pm
Location: San Juan Mountains, CO

What's causing this?

Post by Twin Pinzies » Sun Jun 28, 2009 10:15 am

Here's the story. My 710M's are very well maintained with new filters, plugs, fluids, rebuilt carbs, etc.. They will start up easy and run perfectly all day. The next day I will go to start them and they often will barely start, run rough (like on only 3 cyl.), and puff brown smoke. What would cause it run perfectly one day and then barely run at all after sitting overnight?!
The only way to make them run right is to pull all the plugs and clean/re-gap them. Then it will run fine for another couple days... only to repeat the problem. The plugs are consistently a bit dark and wet across all cylinders when I pull them.
I have an electronic ignition and run 20w50 conventional oil.
Any ideas?

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Erik712m
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Location: Wichita, Kansas

Post by Erik712m » Sun Jun 28, 2009 11:34 am

Do a compression check sound like time for rings.

M Wehrman
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Post by M Wehrman » Mon Jun 29, 2009 3:37 pm

Did you get a load of poor fuel? If they were wet from gas you should be blowing black smoke...
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Twin Pinzies
Posts: 545
Joined: Mon Jan 03, 2005 1:33 pm
Location: San Juan Mountains, CO

Post by Twin Pinzies » Mon Jun 29, 2009 3:59 pm

I think that I found the problem! The oil level was at the high mark on the dipstick. After descending steep grade of 4,400 vertical ft. in only eight miles, I think that all the engine braking ended up sucking in some oil into the cylinders and that was fouling out the plugs. We'll see if this works. I dropped the engine oil level to half way on the dipstick, drove it around a bit, and it gradually ran better and better.

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