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MD Linkage

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David Boelman

New User
I have a problem getting my MD to start on gas. I have had the carburator overhauled. According to the book you are suppose to have the diesel lever back and the throttle in the down position for it to start on gas. However, it does not start with this combination. When I push the diesel lever forward the motor goes over faster than when the lever is pulled back, however, it still does not start. I feel that there must be some linkage problem.
What and how do I check this out.
 
youll need to get a manual , as there is a lot of steps to go through.do you have spark on the gas side?
 
lever must be foward to start on gas . have lever forward and open gas , then check for gas at carb by opening bowl drain ,the check for spark , if mag ,unhook gounding wire from mag to rule out the switch on the manifold .----

anyone reading this or if you know some one with an MD , tell them to drain the carb for winter/long term storage . this spring had to put new float in beause the old cork float had the coating ate away and swelled up to the point the float was sticking to the sides of the bowl !!
 
I will try to get it started with the diesel lever forward. However, I only got spark when I unhooked the mag ground wire. What does this mean?
 
there is a switch in the front part of the intake manifold, the contacts can become fouled and not make a good contact, or you can have a bad switch as well.

Andrew
 
It means the switch in the manifold is faulty, or you had the diesel/gas switchover lever back and the switch was closed, grounding the mag. Some of the older manuals tell you incorrectly that the switchover lever has to be back for starting on gas. Forward is gas position, back it diesel. The switchover lever does 4 things: 1) when forward opens the mag grounding switch so you will get a spark 2)when forward opens the decompression valves for gasoline operation 3)when forward releases the carb float so gas can flow to the carb. when back the carb float is locked up to prevent gas flow in diesel operation and 4)when forward positions butterflys in the manifold so air flows through the carb. When back air flow to the carb is blocked.
 
Best to switch to gas for shut down and run the gas out of the carb until the engine dies. Then shut off gas under the starting tank. Thus no gas in the carb during storage. I guess this problem is why the MD carbs have a drain petcock on them.
 
(quoted from post at 19:49:25 08/02/10) It means the switch in the manifold is faulty, or you had the diesel/gas switchover lever back and the switch was closed, grounding the mag. Some of the older manuals tell you incorrectly that the switchover lever has to be back for starting on gas. Forward is gas position, back it diesel. The switchover lever does 4 things: 1) when forward opens the mag grounding switch so you will get a spark 2)when forward opens the decompression valves for gasoline operation 3)when forward releases the carb float so gas can flow to the carb. when back the carb float is locked up to prevent gas flow in diesel operation and 4)when forward positions butterflys in the manifold so air flows through the carb. When back air flow to the carb is blocked.
Click to expand...

Agreed. Probably 9 out of 10 people have issues with the manifold. The little fork that rotates the shaft has to travel freely and be fully upward on gas. No drag from the shaft or else the butterflies will not close COMPLETELY, which is a must.

I think that "pull back for gas" might have propagated from a later manual for the 400 or 450. Maybe. It seems I read it somewhere in an old MD manual as well, but that memory is badly faded. They are definitely forward for gas.

Also, if it has a mag, is it snapping?
 
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