Smoke coming from head gasket

Hey all. I've got a 77 kz 750 and I let it actually sit and warm up yesterday (was baking exhaust paint on) after about 20 minutes it started smoking from the head gasket, right in front of the engine. The issue is that it was a dark/purple smoke, which tells me that it's burning oil. If I give the bike some gas, I get some purple smoke out the right side exhaust.

Would it be safe to assume I need a new head gasket and new piston rings? Could I be running to rich and the off colored smoke is something I'm not use to. I checked compression, and I was getting a max of 120 psi. I looked through the solution manual and couldn't find where it should be, but I assume somewhere around 150. Also, the spark plugs are a dark color, not sure if that matters. If you need, I can upload a video / pictures of whatever parts you want to see. I just want to make sure I buy all the parts I need when I go to replace things.

Worm drive for the Speedo, if its coming from the #3 area, is way common.

magruder13 wrote: Hey all. I've got a 77 kz 750 and I let it actually sit and warm up yesterday (was baking exhaust paint on) after about 20 minutes it started smoking from the head gasket, right in front of the engine. The issue is that it was a dark/purple smoke, which tells me that it's burning oil. If I give the bike some gas, I get some purple smoke out the right side exhaust.

Would it be safe to assume I need a new head gasket and new piston rings? Could I be running to rich and the off colored smoke is something I'm not use to. I checked compression, and I was getting a max of 120 psi. I looked through the solution manual and couldn't find where it should be, but I assume somewhere around 150. Also, the spark plugs are a dark color, not sure if that matters. If you need, I can upload a video / pictures of whatever parts you want to see. I just want to make sure I buy all the parts I need when I go to replace things.

The engine probably over-heated if it sat idling for 20 minutes without any air flow.

Would consider changing the oil and filter, and performing a compression test.

Good Fortune!

yep.....oh and dont let air cooled bikes sit and run for 20 minutes...that paint is "baked on" after about 3 seconds...doubt ...touch that pipe....

Motor Head wrote: Worm drive for the Speedo, if its coming from the #3 area, is way common.

Motor Head wrote: Worm drive for the Speedo, if its coming from the #3 area, is way common.

Speedo or tach?

Patton wrote: The engine probably over-heated if it sat idling for 20 minutes without any air flow.

Would consider changing the oil and filter, and performing a compression test.

Good Fortune!

It will over heat just idling?!? That sounds like a design flaw to me... I literally just changed the oil, oil filter, and air filter before running it.

It will overheat from idling if you let it just sit and idle over an extended period, but that is not a design flaw. These bikes are air cooled and like all air cooled bikes they rely on air passing over the engine's fins to dissipate the heat; air cooled bikes have no radiator and normally have no fan (although some Police bikes do). Twenty minutes is really pushing it unless you are in a very cold climate. If you want to start the bike and let it just sit and idle set up a large fan and let it blow air over the engine, that will keep it from overheating. Ed

Don't you all know that Kawasaki made a 750 two cylinder motorcycle? :laugh:
76-79 Kawasaki KZ750 is a twin, the four didn't start till 1980.

Tach drive above #2 pipe leaks oil right onto the pipe, it's really common.
10mm o-ring is your friend

steell wrote: Don't you all know that Kawasaki made a 750 two cylinder motorcycle? :laugh:
76-79 Kawasaki KZ750 is a twin, the four didn't start till 1980.

Tach drive above #2 pipe leaks oil right onto the pipe, it's really common.
10mm o-ring is your friend

+1, it is indeed a two cylinder, but I honestly don't think it's that. The smoke was coming from directly between the two pipes.

I've come to think it's probably just the fact that I was cleaning the bike off really well (degreasing) in between the fins most of the morning, but I assumed it all evaporated away. Maybe it left some residue and it was baking it off when the bike got so hot.

Thanks for all the replies guys! Stopped me from doing a whole engine rebuild for nothing!