FROST ON CARB

[ronbass]

My john deere A is hard to start. When it does start the carb frosts up. I have fresh gas in the tractor. It is 45 degrees here in Wisconsin. Plugs are new. wires are good,points gaped right. What the .... Any ideas? Thank you and happy thanksgiving. Ron

 

[Mike Aylward]

That is not unusual at this time of year with the lower temperatures and higher humidity. When the air/fuel mixture is drawn past the carburetor venturi a pressure drop occurs which causes the carburetor to cool (much like an expansion valve in an air conditioner system). As long as the tractor is running properly it is nothing to be concerned about. Hope this helps. Mike

 

[B_Bob]

Natural occurrence in higher humidity environments. Similar to carb icing on piston aircraft engines. Applying carb heat prior to closing the throttle reduces the potential of carb ice to form in the venturi and causing the engine to quit. Not a good thing when you're at altitude.

 

[Kurt_JDB]

Do you know if you have the correct carburetor on your tractor?

I recently rebuilt a DLTX-10 which is for an unstyled B. I put it on my late styled B (which has a much larger engine) for a test.

It iced up pretty good after about 3-4 minuets of running. My assumption was it was pulling a lot more air through the venturi at a higher velocity (because of the larger engine size) than it was designed for.

And, I think this also caused an greater pressure drop on the other side of the venturi hence greater cooling and ice.

So I would love to know if you have a carb for a smaller tractor on your A. Might explain the icing and the hard starting.

Kurt

 

[730d se]

B_Bob, the old joke about what is the fan for in front of an airplane. They says it must keep pilots cool because they really sweat when it stops turning.

 

[Dave (in IL)]

Dang Bob I thought altitude was one of a pilot's best friend. Yessir, altitude and airspeed - get me out of this dead man's zone.

 

[Resting Relics 1]

Hey guys isn't that one of the reasons why Deere went to the heated manifold system on the duplex carbs on the first number series.
John

 

[B_Bob]

Agreed. No argument there, Dave.

 

[gtx1967jewison]

not an issue. what plugs? is the shaft worn on the distributor/ magneto? solid core wires? if not get them. carbon core wont work right. carb could need cleaning - including all the tiny passages usually missed. float level does alot for starting. use the petcocks. keep them open till no more smoke & the plug hits every time.