TOPIC:

Hi all. I've just picked up a 1981 kz750. It has 25,000 miles on it and ran until I started hearing a bad rattle in the engine. Then it began to backfire. Ok so I've started to do a tear down. I pulled the tank, the seat and the battery box. When I took the wires off to remove the battery box not all were connected. The main one I'm concerned about is the one from the ignition part that I believe runs to the coil.
Just to be sure.Near the battery box under the left side cover .There is a round (O) part with two copper bolts and 10 mil nuts also covered with rubber boots. The one with questionable wire is on the right side. The best I can see it has a white wire with a red stripe. I believe it goes to the rectifier. The connection is so loose it would have been just touching. Could this be why the bike would rattle and backfire?
Thanks from Dan in Toronto Canada.

Squeeze the female part (on the white and red wire) until it is tight when you plug them together. Pics?
Steve

there should be 2 wires connected to the positive battery terminal.
One goes to the starter solenoid under the left side cover. The other wire which is white with red stripe goes to the main 20 amp fuse. If your fuse box is original then its a little rectangular plastic box also under the left side cover and to the left of the starter solenoid. A white wire exits from the main fuse and goes to the ignition switch via the harness and connectors in the headlight shell.
A red and white wire also goes from the starter solenoid to the reg/rect
Bad connections could be the source of your problem. Fix em and try again
Good luck

You can download a copy of the shop manual here
kz.bike-night.com/manual.html

It will help you identify the various parts

Thanks diagram is very helpful. I also took off the valve cover to measure the clearance #4 intake is 0.07 others are over at 0.20

Valve clearance should be 0.08 - 0.18 mm or 0.003 - 0.007 inch

Yes 0.08-0.18. I've looked at the pdf and remeasured. Now all are in spec when measured with the cam lobe (90) deg.
Then i found TDC and the timing marks on the cams, it looks like all is good. The marks line up.
Now if I but it all together I'm hoping with the wire fix it works.
I pulled the carbs but cant tell what series they are. I need to find the float measurement. I believe it's 16mm-19mm but not 100% sure.
Thanks from Dan

Don, don't rely on bench measurements. Use the clear tube test. It's more accurate.
Steve

Here is a pic

I don't understand what is a clear tube?

do a search here for "clear tube method".
It's a way to measure the actual level of gas in the bowls. Much better than float height.
fuel level in the bowls should be 4 mm (I think) +/- 1 mm below the seam between bowl and carb body

nice colour bike

Thanks for the info. It looks like a great method. I also like the bike color.
The carbs are not in. Good condition,inside the float bowels was full of rust from the tank (outch!) the primary jets slots are bent where you would but the screwdriver to tighten them,but look clear. Then on two of the overflow tunes there is some king of glue that might be to stop them from leaking where they meet the aluminum the overflow tube being brass.
Do you know what this glue is called I,d like to seal them again because the glue has split in some places but I don't think they are leaking now but soon will be.
I need to get the rust out of the tank. I've pulled the petcock. Drained the tank to get the large pieces out. That was shaking the tank for 45 minutes .then a blow gun on a small air compresser. Now the tank still has rust just nothing loose.
I'm thinking about metal rescue to put inside the tank but not to sure of the best way to stop the rust or seal it from getting worse.
Dan

Thanks