KZ900 not starting

The plugs are dry, black and sooty. Does that mean the plugs are oil fouled or fuel fouled ?
I'll check the valve clearance's and spark Monday when I am off.

I would say you should just give this bike a full engine service that includes points condenser plugs and check timing point gap(obviously) valve clearance and if the battery is a few years old and neglected you should probably replace the battery too. These bikes will run without a battery but they will run poorly. Lastly, take the float bowls off, remove the jets and clean them. Set the float height. If things look really fuzzy in there take the carbs off and clean them. When you have done this report back to us.

BIGKEVIN wrote: The plugs are dry, black and sooty. Does that mean the plugs are oil fouled or fuel fouled ?....

Likely running a little rich (dry and sooty), but not oil fouled (which would be wetter and with more carbon build-up residue.)

Good Fortune!

I checked on this today and decided to check the voltage to the coils and the spark. I checked the voltage of the battery and it was 13.8 volts with the key off. With the key on and the bike not started, the voltage at the battery dropped to 11.75 volts. I checked the voltage at the coils and it was 11.35 volts with the key on and the bike not started. I checked the spark and instead of a fat blue spark, it was thin and yellow. After only few minutes with the key on and trying to start the bike to check the spark, the battery didn't have enough voltage to turn the motor over. I have the battery charger on it and will check it again tomorrow. I'll probably take the battery and have it load tested also. Should there be a 2 volt drop in the battery voltage with the bike off and the key turned on ?

I had someone else check the plugs and was told that they are oil fouled. Is it possible that the valve guides and/or seals need to be replaced ? I have a guy who can rebuild the engine, but needs to find a machine shop before tearing the engine down. While waiting to see if he can another machine shop. I'm wondering if the valve guides and valve guide seals could be the cause of the plugs fouling.

Over filling the engine oil, oil leaking by the rings, oil leaking by the valve seals or just cranking the engine without starting after long storage could oil fowl the plugs. Throw some new plugs in it and fresh gas and try it again. A compression test will give you some answers.

Points and Timing (9 out of 10 times)

• replace points/condensers ($20)
• set points gap
• set timing - VERY IMPORTANT
• make sure the coils are good
• measure voltage through the spark plug wires
• replace the spark plug wire caps ($12)
• new plugs - properly gapped

It might be time to either take it in to a dealer or try to find a KZ gueru in your area to help you out. Most problems are carburetor related probably caused by bad fuel clogging jets and float valves up. There is only so much we can do over the keyboard.

I just did my valves,springs and seals. It ran great but smoked at start up, fouled plugs every 2-400 miles, just didn't have the money to do it. Finally I got everything together. It ran even with oil fouled plugs. The problem must be elsewhere, A lot of times it's the pilot jets being clogged. It's hard to tell because the opening is so small. I use a small guitar string to clean them out. Choke cleaner with the tube to clear the passages. Yes the voltage will drop slightly when the kill switch is turned on. Normal. Lay the plugs on the head touching a bolt turning it over and see if there's any spark. Sometimes a shorted battery will rob the bike of enough power to run it too.
One thing at a time.
Steve

I did check the valve clearance a week ago or so and they were :

#1 intake .076 mm fits
#1 exhaust .127 mm fits
#2 intake .102 mm fits
#2 exhaust .076 fits
#3 intake .051 fits
#3 exhaust .063 fits
#4 intake .063 fits
#4 exhaust .127 fits.

Are these within specs ?

I also checked the compression and it is:

#1 105 psi
#2 100 psi
#3 95 psi
#4 100 psi. These are with the bike cold and the throttle fully open.

0.05 mm-0.10 mm is the spec for 1973-78. Your compression seems a bit low but if they are all close to one another it is just probably worn rings.. It might burn a bit of oil but it will run

Just my opinion but I would try to get those valve clearances closer together......especially the exhaust ones on 2 and 3......they get the hottest and would need more room. Compression #s are ideally measured when motor is hotter with open throttle as you have done