Farm Equipment - D15 Marvel vs Zenith

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D15 Marvel vs Zenith

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=181206
Printed Date: 19 Jul 2025 at 12:10am
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Topic: D15 Marvel vs Zenith

Posted By: DrByte
Subject: D15 Marvel vs Zenith
Date Posted: 15 Jun 2021 at 10:37am

Anyone have an opinion about the carburetor for the D15 ?

I have 2 D15s and having great difficulties with one of them.

Are the Zenith carbs any good?

Thanks for your input !
Steve

Replies:

Posted By: DrAllis
Date Posted: 15 Jun 2021 at 12:15pm

Series 1 and 2 D-15's only had MarvelSchebler carbs. Zenith reliability over Marvel?? I've never seen any difference. What kind of issues are you having ?? Dirty fuel will bother both of them.

Posted By: PaulB
Date Posted: 15 Jun 2021 at 7:21pm

Bone stupid simple carburetors, both them. Find the problem and fix what you have. As DrAllis said, most likely dirt somewhere. The other things could be a worn throttle shaft, a bad float, sticking needle valve or cracked venturi. Not much else it could be.

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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY

Posted By: steve(ill)
Date Posted: 15 Jun 2021 at 7:45pm

A Zenith carb came on a D12 with 139 inch motor... The 149 - 160 inch motors in the D14-15 came with MS carbs....... so the question is, where did your Zenith come from ? Is it large enough / jetted correctly for a larger motor ??? What model carb ?

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Like them all, but love the "B"s.

Posted By: DrByte
Date Posted: 15 Jun 2021 at 11:49pm

Current situation is:

New Odyssey battery, Spark is good, timing is good, compression is good, fresh 91 octane fuel and lead additive, new points, condenser, cap and rotor, new coil, plug wires and plugs. everything gapped properly. 1243 order.

marvel tsx 844 B carb, idle jet 1.8 turns open,

Oil bath air filter removed during this testing.

When attempting to start, the engine responds when momentary choke is applied, tries to catch then dies. Acts like it is flooded. After a few tries, gas begins to drip from the carburetor intake. Adjustment of float resulted in reduction of drip, but still there.

Posted By: DrByte
Date Posted: 15 Jun 2021 at 11:59pm

Thanks Paul !

I will keep the Marvel and rebuild it, hopefully the problem will resolve . As it is, after a few attempts to start up, the plugs foul with carbon and need to be cleaned.

Posted By: DrAllis
Date Posted: 16 Jun 2021 at 7:20am

Why don't you open the main jet a couple more turns to see if it will start and run. Generally speaking, if you leave the choke closed while cranking, the engine should start and stay running, albeit with a lot of black smoke until you open the choke. Also, how do you know the ignition timing is correct, when you haven't made it run ?? You have a carb on a second tractor that works, consider a carb transplant for testing purposes.

Posted By: DrByte
Date Posted: 22 Jun 2021 at 9:33pm

Thanks so much for your help. I ended up rebuilding the Marvel. All seems to be well with the fuel system except for the glass fuel filter that leaks slowly. I am thinking about replacing the fuel line and including a better shutoff valve and filter. Do you have any recommendations ?

By the way, the carb was not the problem. It appears that I have now got a very weak spark, only short orange sparks at the plugs. Troubleshooting that now.