300 and M carb interchange?

Zachary Hoyt · Jun 6, 2012

Took a close look at the carburetor on the 300 and found that the whole back side of the bowl is cracked away. Looking at pictures it appears that an M carb is visually similar, does anyone know if it is possible to use an M carb or carb bowl on a 300? Any advice will be much appreciated.
Zach

Bob M · Jun 6, 2012

Zach - I know the jetting and venturi sizes are different between the M and the 300. But it looks like the bare bowl assemblies may interchange.

My inclination would be to try it!

D Slater · Jun 6, 2012

Anything is possible but they have some different fuel and air metering systems. M can work complete but uses a bigger venturi and may lessen low end power. Choke shafts exit on different sides. Think I may have a extra bowl for your carb thats missing the choke shaft and some other parts you would need to install from yours if interested.
Also the M carb uses a off idle air slot system and some passages are sized accordingly. 300 gas carb has a different idle system in the throttle body and a different jet set up in the bowl and jet size and air passages are sized accordingly. With enough tunning it can work but don't think its worth the trouble for a stock tractor.

cbice · Jun 6, 2012

Hi Zack
they will interchange.
Clif

Andrew Z · Jun 6, 2012

Dave is right, unless you have major engine work you will loose power though the 'M' carb. Very common around here when guys throw a 'M' carb on a C152,C164,C169,C175 (H-350) and find out they have less bottom end etc. If your carb is cracked or inoperative then i would look for the right carb or take the guts out of yours and put them in a 'M' carb.

Andrew

rustyfarmall · Jun 6, 2012

(quoted from post at 07:02:44 06/06/12) Took a close look at the carburetor on the 300 and found that the whole back side of the bowl is cracked away. Looking at pictures it appears that an M carb is visually similar, does anyone know if it is possible to use an M carb or carb bowl on a 300? Any advice will be much appreciated.
Zach

The choke levers are on opposite sides. That is the BIG difference, but nothing that cannot be dealt with. The internals will also be different but will easily interchange.

It is my guess, since the carb bowl is cracked and broken, that at some point that carburetor was full of water and it froze. IF that is what happened, do not expect to find ANY salvageable parts inside. From experience, I can tell you that most likely the throttle bore is also rusted and severely pitted, but don't give up on it until you have a look.

Zachary Hoyt · Jun 6, 2012

Thank you all very much. Here are a couple of pictures of the carb. D Slater, I sent an email about the bowl you mentioned.
Zach

Andrew Z · Jun 6, 2012

I have a 450 that has a similar cracked, ended up JB welding it. Its been holding for a year plus now. You could also braze that too.

Andrew

300 and M carb interchange?

Zachary Hoyt

Well-known Member

Bob M

Well-known Member

D Slater

Well-known Member

cbice

Member

Andrew Z

Well-known Member

rustyfarmall

Well-known Member

Zachary Hoyt

Well-known Member

Andrew Z

Well-known Member

Similar threads