Kaw fh580v smokes black and surges-hunts

[Red Good]

This is a motor I rebuilt prev owner ran no oil . New rods ,pistons , crankshaft , fresh honed cylinders , recut valves and seats , all new seals and gaskets , welded the window in the cases , fresh oil and filter . Starts and runs well for a second and then starts to puff black smoke and hunt , recleaned carb , drilled out both welch plugs and ran a strand on electrical wire through everything . Noticed the skinny little tube had serious corrosion/staining on it . New welch plugs installed and reasembled same thing . Ordered a new Kawi carb . While waiting got it hot and did a compression test , 150 both holes , plugs are sooty as expected . , rechecked coil distance at .010 ok . ran motor with neon plug tested on it , no misfires or anything weird . Install new Kawi carb and it runs exactly the same . Cannot be the carb so checked the fuel pump looks like fair flow , started it and run it and used a pair of pliers to pinch fuel line to about 1/2 flow , takes a minute and it cleans up and runs fine . Release the pliers and it goes back to hunting and smoking black . What the heck is going on ? Any ideas ? 40 years at this and never ran across this . Its on a Toro zero turn maybe 10-12 years old . Help

 

[bertsmobile1]

Try running from a spare tank hooked directly to the carb gravity feeding
IF problem goes away then either the fuel pump diaphragm is punchured or the new carb is for a gravity feed system .
IF the pump is fine, try heating & bending the tang for the float so the float closes earlier .

 

[Red Good]

Tried that this morning , gallon test can 12 inches above the carb , starts and run puffs black and hunts same as before . Tank has a knob to shut off fuel so turn it 1/2 off and it starts to get better at 1/4 it runs really nice . Are jets available for these carbs , cannot find a size on the stock jets . Thanks guys .

 

[hlw49]

Check the choke.

 

[bertsmobile1]

So we are making progress,, sort off
has to be in the carb.
Stock jet should be 92063-7037 which is a # 105 size

Have you tried backing out the pilot air jet on the top of the carb
This actually does make a difference to the dynamics of the fuel flow in the main jet

Also double check the timing key because if the key sheared when you were holding & tightening the flywheel that will lead to a retarded spark
I used to check the valve timing & Spark timing by wrapping some masking tape around the flywheel then I came across this app on the web to print out timing tape.
If you print it onto self adheasive paper it will stick to the flywheel but I use plain paper & spray glue
timing tape printer
timing disc printer if you prefer

 

[slomo]

used a pair of pliers to pinch fuel line to about 1/2 flow , takes a minute and it cleans up and runs fine . Release the pliers and it goes back to hunting and smoking black .

Old carb needs to be pressure tested at the needle and seat. New Kawi carb was never tested either.

gallon test can 12 inches above the carb , starts and run puffs black and hunts same as before . Tank has a knob to shut off fuel so turn it 1/2 off and it starts to get better at 1/4 it runs really nice .

So stopping down the fuel flow, engine cleans up and runs better. Tells me the needle is sticking open and likes your new 1/4 valve opening to get proper A/F ratio.

 

[slomo]

Check the choke.

OP states engine runs clean (really nice) at 1/4 valve opening off tank.

 

[Red Good]

Check the choke.

Done , not the problem .Thanks

 

[Red Good]

So we are making progress,, sort off
has to be in the carb.
Stock jet should be 92063-7037 which is a # 105 size

Have you tried backing out the pilot air jet on the top of the carb
This actually does make a difference to the dynamics of the fuel flow in the main jet

Also double check the timing key because if the key sheared when you were holding & tightening the flywheel that will lead to a retarded spark
I used to check the valve timing & Spark timing by wrapping some masking tape around the flywheel then I came across this app on the web to print out timing tape.
If you print it onto self adheasive paper it will stick to the flywheel but I use plain paper & spray glue
timing tape printer
timing disc printer if you prefer

Will check the wheel and key , 3 carbs now all the same ,pilot adjustment in all the way out all the way makes no difference . leads me to beleive its not the carb . Thanks guys .

 

[slomo]

Pressure test the carb needle yet?