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Military MEP and Aircraft Gen-Sets

Fuel/Oil Ratio on J-321

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Old 03-06-2011, 05:49:02 PM
Patrick62 Patrick62 is offline
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Default Re: Fuel/oil ratio on J-321

You are mostly ok to use the newer oil mixtures.
I hang out here a lot, and we are quite a conglomeration of folks running some very old saws.

The old jacobson was designed for 30wt non-det oil, which isn't that great a 2 cycle oil hence the need to run it at 16:1
Newer oil is far superior, and can run very well at the 40 or 50 to 1 ratio.

What would I do? I would probably run that thing like my old Lawnboy which worked for years (and years, and years) at 32:1 with ashless oil. It had the needle bearings in it as well. I don't think that a jacobson is any better or worse than that OMC engine.

My 2 cents worth
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Old 11-27-2011, 08:39:49 PM
JakeSecor JakeSecor is offline
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Default Re: Fuel/oil ratio on J-321

Being a Jacobsen mechanic from the 60's, I recall that the 321 engine could be run on a 32:1 mixture (that's why it was called the 321 engine - for 32:1). The Lawn Boy ran on 8:1 then 16:1 (I believe for the "D" series engines) so the Jacobsens ran on a leaner mixture.
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Old 05-11-2018, 05:43:34 AM
Victor B Victor B is offline
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Default PU-181A metal fuel cap

I picked up this little genset at an estate sale last week. It was seized and appeared to have been at least partially submerged. The engine is now free and with the exception of a fuel line, repairing of a hole in the tank, finding a replacement reed valve and locating a fuel cap it is ready to run!

The fuel cap is brass/bronze and about 2" in diameter with two little ears for gripping. If anyone has an idea for a source of this fuel cap I'd appreciate hearing from them. Also I need a piece of reed valve shim steel, I've seen .004 as the thickness but I have no idea where to find it. Thanks in advance!
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