Kawasaki FD661D Still hunting after new carb.

[RMR]

I'm working on a liquid cooled Kawasaki FD661D that came in with a blown head gasket. Before addressing the very minor coolant leak in the cylinder, the first thing I noticed is that the engine was hunting badly when cold. After running for 10 minutes it will finally stop hunting and run normal. I contacted the customer to ask if he ever had that problem, to which replied, no and that it is a new carburetor. With that knowledge I proceeded to fix the head gasket and went ahead and cleaned the carburetor while it was off.

Everything back together and it still hunts when cold and eventually stops after getting good and warm. I checked the base of the carb and intake for leaks and found none.

So that's why I'm here....... Suggestions??

Thanks
Chad

[RoyM]

Hold your finger on the throttle shaft, if it smooths out the governor is too sensitive. If it stumbles and dies there is a fuel delivery problem or an air leak. Did you install a cheap aftermarket carb?

[creia]

Hold your finger on the throttle shaft, if it smooths out the governor is too sensitive. If it stumbles and dies there is a fuel delivery problem or an air leak. Did you install a cheap aftermarket carb?

I read the OP (RMR) as stating that it came to him with a "new carb" already installed as stated by the owner. But yes, good question- Can you tell if it is an OEM or aftermarket carb?
Michael

[KE4AVB]

The coolant into the cylinder be the cause as if the customer is running 10% ethanol fuel the water can lower the octane of the fuel. I would solve the coolant leak first and then if still surging work on that problem.

[RMR]

Holding the throttle the engine smooths out but drops RPMs. As far as I can tell the carburetor is OEM. Customer said it was $300. And it's marked TK, which I believe is a OE brand for the Kawasaki's.

Coolant issue has been resolved already. Carb still hunts.

[RoyM]

Can you do a static governor adjustment and possibly reposition the spring further from the pivot? You would then need to readjust the top no load speed.

[RMR]

Can you do a static governor adjustment and possibly reposition the spring further from the pivot? You would then need to readjust the top no load speed.

Good call being the owner did the new carb himself. However I just checked the adjustment which was good, and it does not have any spring position options.

[KE4AVB]

I would check to see if it is a lean burn condition by adding a little choke. If it smooths out then probably the idle mixture jet(s) are too lean and need resizing or the air bleed jet(s) are too large. This is provide you are testing off load.

[Arkie]

I would check to see if it is a lean burn condition by adding a little choke. If it smooths out then probably the idle mixture jet(s) are too lean and need resizing or the air bleed jet(s) are too large. This is provide you are testing off load.

The OP says it only hunts when cold, eventually smooths out after warms up. Adding a little choke, even by just using your fingers across the carb throat sometimes will give you a hint.

On some engines, especially Emergency generator engines I've carefully enriched the idle jet with good results. Hunting and surging voltage on a generator is not a good thing.
I usually see if I can find a replacement jet before I attempt. (some idle jets are replaceable and cheaper than a replacement carb and I know that I can get back to OEM jet if things get worse) If no replacement jet available I have to be more careful.
I use the mini micro drill bits with the small manual keyless chuck


I try to find the better made bits to reduce chance of twist off and have to go slow and easy.
If you twist/break one off in the hole you are SOL.

Al Gore and the lawn mower police may come to visit you and the engine may not pass a emissions test when it starts running smooth after the jet change.

[RMR]

I would check to see if it is a lean burn condition by adding a little choke. If it smooths out then probably the idle mixture jet(s) are too lean and need resizing or the air bleed jet(s) are too large. This is provide you are testing off load.

The OP says it only hunts when cold, eventually smooths out after warms up. Adding a little choke, even by just using your fingers across the carb throat sometimes will give you a hint.

On some engines, especially Emergency generator engines I've carefully enriched the idle jet with good results. Hunting and surging voltage on a generator is not a good thing.
I usually see if I can find a replacement jet before I attempt. (some idle jets are replaceable and cheaper than a replacement carb and I know that I can get back to OEM jet if things get worse) If no replacement jet available I have to be more careful.
I use the mini micro drill bits with the small manual keyless chuck


I try to find the better made bits to reduce chance of twist off and have to go slow and easy.
If you twist/break one off in the hole you are SOL.

Al Gore and the lawn mower police may come to visit you and the engine may not pass a emissions test when it starts running smooth after the jet change.

I have adjusted the idle mixture screw a few times with no real results. However I did reach out the the owner to see if he still has the original carburetor. If so, I may try comparing the two and possibly swapping it out.

Thanks