1977 KZ650. Top end rebuild? Hope Not!

The other day I was riding the bike and something wasnt right.

I thought it was the plugs so I went out and bought new ones.

When I pulled out the old plug, all of them were decent except cylinder #1. It has a bit of oil on it. So, I changed the plugs and started up the bike. After it ran for a bit I pulled plug #1. It wasnt oily, but it was BLACK.

I put it back in and started the bike up again. I noticed on the left hand exhaust (same as on cylinder 1 side - which is the left hand side), smoke comes out when I roll the throttle.

Time for a rebuild?

How long since the last valve adjustment? Compression test results? (don't waste time checking compression unless the valves are adjusted properly). Condition of the carbs? All new O-rings and properly sealing float needles? How long since the points and condensers have been replaced? Plug wires? Voltage to the coils? New plug wires and resistor caps? Is the bike stock or modified?

Bottom line: do all the various maintenance items that a 40 year old bike demands, then see what needs further work. Most of the time running problems can be traced back to neglect by some owner in the vehicles past history.

Nessism wrote: How long since the last valve adjustment? Compression test results? (don't waste time checking compression unless the valves are adjusted properly). Condition of the carbs? All new O-rings and properly sealing float needles? How long since the points and condensers have been replaced? Plug wires? Voltage to the coils? New plug wires and resistor caps? Is the bike stock or modified?

Bottom line: do all the various maintenance items that a 40 year old bike demands, then see what needs further work. Most of the time running problems can be traced back to neglect by some owner in the vehicles past history.

Thanks for this.
I could be wrong, all my friends are telling me this problem I am having points to a bad piston ring. The issue is cylinder 1 with oil on the plugs and smoke coming out when I roll the throttle. Im focused on a specific problem, meaning I doubt its:

The ignition coil,
The points or condenser
The plug wires
I dont think these things are whats making cylinder 1 spark plug black and oily.

By my friends accounts, what I am experiencing is bad piston ring or something of that nature.

You haven't answered any of my questions.

You have no chance for a properly running bike unless all the basic maintenance is up to date. Do that and then see how well the bike runs. If it still doesn't run properly you will at least know what the problems is not.

ALL of the maintenance was done 6 months ago, ahead of the season, and everything was in working order.

Now I have a specific problem Im trying to get to the bottom of.

I just may give away this bike to anyone who wants it. Stay tuned.

I suggest going back to basics...

Compression check
Spark check
Fuel level in each carb using the clear tube method
Verify carb sync and settings of fuel/air screws as appropriate
No vacuum leaks
Airbox fully sealed and air filter clean

Nessism wrote: I suggest going back to basics...

Compression check
Spark check
Fuel level in each carb using the clear tube method
Verify carb sync and settings of fuel/air screws as appropriate
No vacuum leaks
Airbox fully sealed and air filter clean

Im going to take your advice. I will come back with my findings next week

How many miles are on the engine? Also, what spark plugs are you using? Ed

650Dude wrote: ALL of the maintenance was done 6 months ago, ahead of the season, and everything was in working order.

Now I have a specific problem Im trying to get to the bottom of.

I just may give away this bike to anyone who wants it. Stay tuned.

I hope you're not serious about giving it away because of a little oil on the plug. Don't get discouraged. Many years ago I got my '78 650 with 8k on the clock. It had low compression and oil on the plug in #3. I didn't have the money to fix it and I wasn't worried, it pulled to redline in 4 gears and I didn't care how fast it would go in 5th so I was just going to run it. I kept up on valve adjustments and it now has 83,000 miles and still pulls to redline in 4th. The compression is still about the same as it was before. I think if you don't want to do the top end it's not going to hurt anything to just ride it.

Looks more like an leaking valve stem seal, they will get hard and brittle and let bypass oil. specially #1 cylinder will fill with oil if parked the bike on the side stand.

Scirocco wrote: Looks more like an leaking valve stem seal, they will get hard and brittle and let bypass oil. specially #1 cylinder will fill with oil if parked the bike on the side stand.

Did you have to take the whole engine out?

No, top end comes off in the bike. Good time to inspect the cam chain rollers and guide.
Steve