Kawasaki FD750D-AS04 running poorly

Auto Doc's said:
Your description favors a very worn cam.

Gummed up main jets are also a real issue if it only runs with choke,

The fuel anti backfire valve will also produce similar results when it is not working. Full choke will pull fuel past the shutoff and allow it to run as a "get it in the shop" measure. Shutoff solenoids do gum up and get sticky or quit working.
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I have removed the main jets and have both sprayed them out and also cleaned any old residue out with a wooden toothpick. And the fuel solenoid has been both operated by hand to make sure it wasn't sticking and also bench tested to make sure it is retracting. It seems to run relatively good at fuel throttle without choke. The choke in only needed when starting and also trying to get it to idle.
 
ILENGINE said:
I have and with no change. So I don't think leaking that much air around the shaft. Leakdown testing shows less than 15% bypass at TDC so at least top of stroke the rings, head gasket and valves are sealed.
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This why you to the modified leak down test on OHV engines so you can all of the stroke. Can't be done on L-heads but quite easily done on OHV engine. Taper and oval is more pronounce at the middle and bottom of the stroke.

I had several years ago a Tecumseh horizontal that was giving running problems when I cam with the modified test and found the lower part of the stroke badly worn out.
 
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ILENGINE said:
I have removed the main jets and have both sprayed them out and also cleaned any old residue out with a wooden toothpick. And the fuel solenoid has been both operated by hand to make sure it wasn't sticking and also bench tested to make sure it is retracting. It seems to run relatively good at fuel throttle without choke. The choke in only needed when starting and also trying to get it to idle.
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Hello ILENGINE,

Does this carburetor have the top plate on it with 3 screws? If so....

The carburetor can usually stay mounted, perform the following:

Remove the top plate and gasket carefully. You will see the right and left channels and some very tiny holes. Use a very fine strand of wire such as an instrument tenor string or a single wire pulled from a wire hand brush to clean the small holes out. Do not try to jamb anything soft into the holes. Clean out with carb spray lightly.

Then put the gasket and plate back in place and snug the screws down. Don't overtighten the screws.

Those very tiny holes are the idle bleed air passages.

Hope this helps you.
 
Auto Doc's said:
Hello ILENGINE,

Does this carburetor have the top plate on it with 3 screws? If so....

The carburetor can usually stay mounted, perform the following:

Remove the top plate and gasket carefully. You will see the right and left channels and some very tiny holes. Use a very fine strand of wire such as an instrument tenor string or a single wire pulled from a wire hand brush to clean the small holes out. Do not try to jamb anything soft into the holes. Clean out with carb spray lightly.but may

Then put the gasket and plate back in place and snug the screws down. Don't overtighten the screws.

Those very tiny holes are the idle bleed air passages.

Hope this helps you.
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This carb has a 2 screw cover that covers a cavity that basically acts like the fuel bowl vent. It has separate air bleed screws that can be accessed from outside the carb. I have blown carb cleaner through the air bleed but may go back and recheck with running wire through the air bleed holes.

Also when I get a chance may pull the rockers to do another leakdown test.
 
Update. It appears that there are sources that have the compression for this engine incorrect. The source I came across say compression was supposed to be 107. But that is a misprint and is actually supposed to be 170. Gentleman we have a compression problem.
 
ILENGINE said:
Update. It appears that there are sources that have the compression for this engine incorrect. The source I came across say compression was supposed to be 107. But that is a misprint and is actually supposed to be 170. Gentleman we have a compression problem.
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Hello ILENGINE,

I looked on Parts tree and it shows the cam along with a small return spring, so my assessment is that this cam has a compression release. 107 PSI cranking compression is actually decent compared to others I have seen.

Not sure how or if 170 PSI can be achieved with a compression relief camshaft design.
 
Auto Doc's said:
Hello ILENGINE,

I looked on Parts tree and it shows the cam along with a small return spring, so my assessment is that this cam has a compression release. 107 PSI cranking compression is actually decent compared to others I have seen.

Not sure how or if 170 PSI can be achieved with a compression relief camshaft design.
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Straight from the FD750D service manual

Compression Measurement
• Before measuring compression, do the following.
􀀀 Be sure the battery is fully charged.
􀀀 Thoroughly warm up the engine so that engine oil between the piston
and cylinder wall will help seal compression as it does during normal
running.
􀀀 Stop the engine.
• Disconnect the spark plug caps of each cylinder and remove the spark
plugs.
• Attach the compression gauge assembly firmly into one plug hole.
Special Tool - Compression Gauge: 57001–221 [A]
Compression Gauge Adapter: 57001–1159
• Ground the spark plugs to the engine.
To avoid fire, do not ground the spark plugs in closed positions
to the plug holes. Keep the plugs as far away as possible from
the plug holes.
• Using the starter motor, turn the engine over with the throttle fully open
until the compression gauge stops rising; the compression reading
obtainable.
• Repeat the measurement to the other cylinder.
Cylinder Compression (MIN): 1171 kPa (170 psi)
 
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