starting hard when warm

[Greg Buechner]

1950 side mount 6 volt. Wouldn't start when hot without ether. Starts great cold. Took the advise of members and replaced the wiring, points, cond., coil, etc. It really needed it. Good spark when warm or cold. Did notice that there was a little play in the dist. shaft bushing. What a hack job over the course of 60 years.

Still wouldn't start when warm. Went into the carb and found the float was set at close to 1/2" instead of 1/4". She starts better when warm but needs choke and needs to turn over quite a bit.
Any tips to make her better?

 

[Bob]

Having to use the choke and crank it a bit is BETTER than the opposite problem of "nearly always floods"!

 

[HCooke]

Use a short wire with aligator clips on it to jump around the iginition switch. I had these symptoms this summer - cause was a faulty switch.

 

[Greg Buechner]

I did the switch by pass and that didn't help. The spark is good. The timing is correct.
My only thoughts would be the side to side play in the rotor shaft bushing or carb adjustments.

Perhaps the bushing expands when warm causing it to have even more play, throwing off the points.

But it did also get easier to start after the carb float adjustment.

 

[Scott3743]

Many old engines (before 1960) which were in need of a carburetor rebuild, especially those with a cast iron carburetor, found that the engine carburetor would create what was commonly called a "Vapor Lock".

This condition was caused by the unused fuel sitting in the carburetors bowl becoming warm and vaporizing in the bowl from the heat that was transferred from the engine and the exhaust manifold after the engine was shutoff. The vaporizing having no place to go, would block new fuel from entering the carburetor when attempting to restart the engine, hence the term "Vapor Lock".

To remedy this situation, the driver would either wait for the vapor in the carburetor to return to it's original state of liquid fuel or would allow the vapor lock to escape by draining the bowl through the drain plug/nut on the bottom of the carburetors bowl.

I of course have no way of knowing if this is the reason for your problem, but like all others responding to your comments, felt that it was something for you to consider.

Scott

 

[Anonymous-0]

That is just complete nonsense. Barring a plugged vent on the carburetor, as fuel vaporizes the float will drop and admit new fuel. Vaporization would cause hard starting from a rich condition(too much fuel) rather than fuel starvation as you imply. Vapor lock rarely happens on a gravity flow system. It happens on the suction side of a fuel pump system due to a decrease in pressure which can cause percolation. Since the pump is designed to pump liquid not vapor, the fuel system is locked.

 

[Ramrod]

That really sounds like a carb problem to me. I hate carb problems, but I have learned in 50 plus years of rebuilding them that my best solution is just to go buy a new carb, which has always fixed my carb problems.

 

[Greg Buechner]

I put a complete carb kit in and it sure made things better, especially with all the new wiring. She fires immediatly when cold with little choke, if any, and then a little choke until shes run up to speed. I haven't counted the seconds it takes to fire up when shes warm but, it is longer.
As long as the battery doesn't go dead I'm OK with the prolonged starter time when she's warm.

Perhaps I may look at a new carb in the future.

 

[Ramrod]

After I rebuilt my NAA, it ran great, but sputtered at 1500 rpm, which is bush hog speed. I rebuilt the carb carefully and it ran the very same way.

I bought a new carb which fixed the problem, years later, it still runs well and bush hogs all day long. I think the cast iron carbs get pitted eventually and require replacement.

 

[Greg Buechner]

Hey Ramrod,
Which brand carb did you buy? Did it come with the proper jets etc?

 

[Ramrod]

I bought a Tisco from a friendly dealer that I trusted. It may be the only Tisco part that bolted right on and worked straight away.