KZ750B Twin Tuning Help Needed!

Hey dudes. Could use a little advice. I have a very nice KZ750B with 13,000miles on it. I just got it running this year. It isn't running too good. It will idle at 1000 rpm but has a stumble when you get on the throttle. I took the carbs off and checked them over. Look clean inside. The little tiny holes in the spray bars are clean as a whistle. Think it could be points or timing? The plugs look good.

speedadict wrote:

Hey dudes. Could use a little advice. I have a very nice KZ750B with 13,000miles on it. I just got it running this year. It isn't running too good. It will idle at 1000 rpm but has a stumble when you get on the throttle. I took the carbs off and checked them over. Look clean inside. The little tiny holes in the spray bars are clean as a whistle. Think it could be points or timing? The plugs look good.

If it hasn't run in a year, you need to drain the tank and flush it. Flush the fuel lines and replace the filters. Run cleaner through the carbs and I would check the fuel levels. Checking compression is a good idea. Check points and gap, check timing.

Does it have stock pipes, jets, and air filters?

It is probably old fuel. Now it is in the engine.

The fuel cleaner is a great idea too. I like "Sea-Foam", you add it to the gas.

I dumped in a fresh gallon of gas, and did add sea foam. It still is doing it... I took the bottom of the carbs off, and they are clean. I was wondering about timing as well, but I don't know how to time anything but a small block ford. Still stumped. It has stock carbs and a Mac two into one.

Ok kawboys, I "tweeked" the timing a little and it seemed to help. Now I have discovered another problem. I have a leaking valve cover gasket. Does anybody know where I can get one?

If you guys search the forum for "zero hero" you will find a thread called KZ750 from zero to hero. The blue bike is the one that I am working on. Thanks!

speedadict wrote:

Ok kawboys, I "tweeked" the timing a little and it seemed to help. Now I have discovered another problem. I have a leaking valve cover gasket. Does anybody know where I can get one?...

Yep, I went over every little thing on my bikes, and over time, went over it all again as I learned more and more... and also as each change I made affected other things.... My advice is to check and verify and check and verify and check and verify and.....



Oh, the gaskets... they pop up on eBay now and again. I just bought one... make sure you get the ones for your year, since the early 750 twins ('76-79) have a different gasket than the later ones...

And make sure it's the valve cover gasket that's leaking, and not the tach cable seal. I have never had a KZ750 twin with a leaking valve cover (I have had six or eight), but about half of them had leaking tach cable seals.

If you see smoke coming from the right front corner of the motor when you park it after a ride, you have a leaking tach cable seal.

speedadict wrote:

Ok kawboys, I "tweeked" the timing a little and it seemed to help. Now I have discovered another problem. I have a leaking valve cover gasket. Does anybody know where I can get one?

If you guys search the forum for "zero hero" you will find a thread called KZ750 from zero to hero. The blue bike is the one that I am working on. Thanks!

Old Bike Barn sells cover gaskets for the 1979 750T:

www.oldbikebarn.com/Motorcycle_Parts/Val...n-Valve-Cover-Gasket


If it is the 1979 B-4 model with Mikuni BS38's I can help you tune it because I just tuned mine to run with MAC 2-1 headers.

On mine, I also had BAD low end throttle hesitation. If your MAC is like mine, this is the best setup: I had to increase the pilot jets up to #50 and also move the jet needle clips to the lowest (richest) setting to get it to run decent. Set fuel bowl level to stock (5.5mm). FYI, the stock #125 mains run best on mine. If your carbs are not BS-38's, this advice may not be usable.