Farm Equipment - Question about B model

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Question about B model

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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=8992
Printed Date: 20 Jan 2025 at 2:55am
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Topic: Question about B model

Posted By: RobbyH
Subject: Question about B model
Date Posted: 04 Mar 2010 at 10:51pm

I am seriously looking at a 40's B model that looks real good. The issue I have is that while it idle good, as you rev up the RPM's it wants to sputter as if a coil is going bad, points bad (has been converted to a distributer from the magneto) or a carb issue.

The question I have is (1) would either of these three cause a sputtering issue; (2) any thing else that might cause it and (3) since it hasbeen converted to a distributer, how hard is it to find points, etc for it or to convert back to a magneto?

Thanks

Robby

Replies:

Posted By: FRANKO
Date Posted: 04 Mar 2010 at 11:44pm

Yes, what you have identified could cause sputtering or missing. I would check out in order of most likely reason first,

1. Lack of fuel. Could be a restriction from the tank into the carb, a dirty carb, or carb load jet adjusted too lean.

2. Weak spark. Could be caused by corroded points, weak condenser, or weak coil, or a low voltage to the coil. If your tractor has the later model Delco distributor, parts are readily available at an auto parts store or from vendors on this site.

3. Bad spark plugs.

4. Leaking intake valves caused by burned valves or misadjusted valve clearance. Check compression pressure in each cylinder with the spark plugs out. They should all be within 10PSI of each other.

It is a good idea to check timing. That could cause a lack of power but generally will not cause sputtering. If you do all of the above you will have done a good tune-up and assuming the valves check out OK, it should run well.

Posted By: Thad in AR.
Date Posted: 05 Mar 2010 at 6:17am

Did they put a distributor on it or try to make a distributor out of the mag? I bought a b once that they used the mag for a dist but it wouldn't advance the timing and wouldn't rev. I put a different mag on it and it runs great.

Posted By: ACJohn
Date Posted: 05 Mar 2010 at 8:50am

The fact that is runs is key. Unless the price is an issue, if you can fix it yourself, the "fix" to the issue shouldn't cost too much unless you are buying a mag. Then you're looking at about $300 outright for a rebuilt "hot" one that will light 'er up with a 1/4 crank!!