TOPIC:

Picked up this gem for $600. 78 kz750 twin. 16k. Had been sitting in a garage for the last twelve years. I cleaned the carbs and petcock, (they were nasty,) new plugs, new fuel lines and filters, cleaned air filter, adjusted and cleaned points, put some gas in it and it fired up first kick! These Kaws never cease to amaze me.

I did have to replace one of the floats however. It had a small hole that filled up with gas. Other than that the bike is in really good condition. Took it for a little ride today and it performed flawlessly. It can't touch my kz650 in terms of speed though

Is that original paint by the way?

Nice find and that is a repaint..

The kz1000a seat and tail look very good on your twin. I'm going to do that same modification to my 78. Do you have any more photos?

Nice bike, they are very tuff machines. My brother rode one to Central America in 1997 on some very hard roads and it never failed him.

Nice, all the old kawasaki's are so nicely styled.

This 750 twin was (I think) a bit of a disappointment for kawasaki in sales figures, I think they wanted to tap into the xs650 market for the US but didn't.

Sometimes the less desirable bikes to the 'collectors' are now rarer than the iconic z1, H2 , Lawsons etc. Nice find!

That's awesome Baldy! I want to do something like that sometime.

And yeah, from the research I did, the 750 twins didn't sell that well. The inline fours were just killing it. They say they're super dependable though.

It developed an issue today. Feels like it's got only half the power and there's alot of smoke coming out of the left side exhaust. The smoke is a grey/dark grey color. The left side is firing but when I pulled the plug it had gas on it. Im assuming its getting too much fuel. The carbs and airbox are stock so I figured there was too much fuel in the float so I bent the float tab up alittle and the problem still persisted. Gonna pull the carbs and clean again tomorrow. Any other suggestions?

I'll take some more pics tomorrow

Black smoke from exhaust may indicate a too rich air-fuel mixture for whatever reason, and may smell of gasoline.

Blue-grey smoke from exhaust may indicate excessive oil burning for whatever reason.

A leak-down test can help diagnose whether compression from inside the cylinder is being lost into the crankcase.
If the compression rings are worn, the oil ring may also be worn.
But the oil ring may be defective for whatever reason and allow oil burning evidenced by blue-grey exhaust smoke even where the compression is okay.


A leak down test injects air pressure through the spark plug hole to pressurize the combustion chamber.

Can perform a poor man's leak down test by introducing compressed air into a spark plug hole and listening to where it escapes from the combustion clamber. This may be done at TDC or any other cam positions where both valves are fully closed. Top dead center (TDC) is when the piston is at its highest position. An easy way to tell TDC is by alignment of the T mark with the case mark when viewed through the timing window.

May introduce a spurt of compressed air by using a rubber cone-tip blow gun (rubber air nozzle) held into the spark plug hole. And of course keep holding it in position to keep air from coming back out the spark plug hole while listening for escaping air at other places. The air compressor should not be running while listening because the noise will likely drown out any sound of escaping air. Or just use a portable compressed air tank.

Air heard escaping from exhaust port indicates exhaust valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from carb intake indicates intake valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from crankcase breather indicates loss of compression past rings into crankcase (perhaps worn piston rings or cylinders).

Air heard escaping from head gasket area indicates indicates loss of compression past head gasket (perhaps due to a blown head gasket).

A leaking valve may sometimes be resolved by adjusting the clearance to within specs.

A leaking head gasket may sometimes be resolved by torquing the head fasteners when the engine is stone cold (such as after sitting overnight).

As a leak-down test deals with compression loss, it isn't much help toward diagnosing a broken or otherwise defective oil ring.


Good Fortune!

vondikka wrote: ... The left side is firing but when I pulled the plug it had gas on it. Im assuming its getting too much fuel. The carbs and airbox are stock so I figured there was too much fuel in the float so I bent the float tab up alittle and the problem still persisted. Gonna pull the carbs and clean again tomorrow. Any other suggestions? ....

The fuel level should be within specs as evidenced by the clear tube test.

In my opinion, it is ill-advised to lower the float height in a misguided effort to add more pressure toward pushing a leaky float needle harder into it's seat.

Where the fuel level is within spec, and the float valve is leaking, the issue is usually with the float valve (which is likely dirty or worn out), and the issue is not the fuel level, and won't be remedied by setting an out-of-spec fuel level.

Having the correct fuel level is critical to all carb mixture functions.

Good Fortune!

Great score for the money.

Ok, thanks Patton. Gonna try the leak down test tonight.

Ok Patton, I did the leak down test and the air just came right back out of the spark plug hole. All good right? It was the left side that I forced the air into. Is that correct? When blowing into the right side, the air escaped through the exhaust.