[bob54]

It looks like a Diesel blowing black smoke. Idles rough and dies. has miss at high speed. Runs the same warm or cold
I have:
Checked timing, it is perfect
Checked compression 90 lbs
Removed air filter intake tube
Leak down test. No leaks at intake with carb removed, or at exhaust. Engine held pressure.
Adjusted valves
Replaced spark Plug
Replaced carb, adjusted screw to 1 1/2 turns out
Tried a different coil
Sprayed around the intake boot with brake clean, No leaks found
I tried holding a piece of paper at the exhaust and it does not suck into the pipe, in fact tore the paper.
Any ideas are greatly appreciated. I am out of them
Thanks

 

[Mech]

Does it have a vacuum operated fuel tap..
Or, a charcoal canister for emission control..
The tap has a diaphragm that gets a hole and lets fuel down the vacuum hose.
The canister can get flooded and then breathe rich fumes or fuel into the engine..

 

[Mech]

And same behaviors with both carbies ?
And the old carby had been running ok for a while ?

 

[bob54]

good question,,,I'll take a look

 

[bob54]

Fuel is gravity fed from the tank to the carb. The only other line from the crab are overflow lines and they are dry.
Could I have a problem with the Stator pickup or the CDI?

 

[Mech]

It's possible. If there is lots of black smoke though I'd be suspecting the carb. When you checked the timing, was that the ignition timing? With a timing light ? Did you see a lot of misfiring ?
If it was just firing every second time or something because of bad ignition then it would still only be burning the right amount of fuel, just a bit erratically, but a lot of black smoke tends to make me think there is a lot more fuel than required.. sort of thing.

I'd strip and clean a carb, probably the old one, and make sure it wasn't that as my first step..

 

[bob54]

It did it with a replacement carb.

 

[Savage]

Bob,
What color is the spark? Look at plug while cranking.

Was the replacement carb OEM?

Please answer questions related to timing that Mech posted.

 

[d0nbennett]

Might want 2 check your fuel pressure as, if it's out-of-spec, that could cause the flooding.& black smoke. (I assume there's an in- tank fuel pump or similar. It may feature a built in regulator that could be the cause.)

 

[Mech]

Put a timing light, or one of the gadgets that go on the plug and tells you whether there's spark or not, and see it the spark goes intermittent at revs..
Check the breather hoses on the carb and tank.

It could be carb and it might just be cdi or ignition.. I'd make bloody sure the carby was clean and adjusted and getting good fuel before I went "trying" a cdi or stator.