1977 KZ650 not running properly

Hi guys. I worked on my bike tonight. I cleaned the carbs thoroughly removing the jets and using carb cleaner and compressed air but I still have some issues.

here are the exhaust temp after idling for 5 minutes: 1= 150F 2= 200F 3= 230F 4= 250F
This is just estimates as I took those measure with a cheap infrared thermometer and it always fluctuate).

I first though that #4 was the one running better but after some reading here it may be that this one is running lean (like folks having gold exhaust from running lean). Can someone explain a little about that?

#1 need work and #4 isn't right also. How to know what would be the good exhaust temp? (I guess it's not about getting a specific exhaust temperature but it helps figure out how it's running).


Another issue I have. I need to adjust the idle many times as it warms up. I turned it down maybe one turn after every minute I drive and stop (short test drives) Once again that's just a figure. Do you play with that screw often (everytime you ride) or once the idling speed is ok there's no need to mess with that? Do you start it on choke and once you turn it off the idling speed is ok? I sprayed carbs cleaner to find a vacuum leak but can't find any!?

Also, when I get the idle lower than 2000 rpms the engine run kind of rough and I can hear the primary chain (I guess) making noise.

I read the SM but don't wanna go through all the step of synching the carbs and all those adjustements without knowing it would fix my problems. I don't have much time to spend on this and I need the bike to go to work asap.

Thanks for your help!

If the bike will not idle below 2000 rpm the vacuum leak test is unlikely to reveal a leak. That test works best when the engine speed can be temporarily adjusted very low (well under 1k rpm). This is because at that point the carb slides a pretty much closed which raises the vacuum level in the carb holders. This in turn increases the odds that the carb cleaner will be sucked in through any leaks and will have a noticeable affect on the engine idle.

It is possible that the carb cleaning missed some little orifice, but before you go through the trouble to pull and re-clean the carbs I would highly recommend you sync the carbs. If one or two carbs are open significantly more than the others the idle will be affected, the primary chain will make a lot of noise at idle, and the cylinders will run at different temperatures. If you have access to a sync tool or proper gauges syncing the carbs is a very easy process and does not take long to do. As you sync the carbs you should be able to lower the idle speed to a normal rate. At that point you can perform the leak test again and see if it reveals anything.

You should not need to fiddle with the idle speed adjuster during a ride once the carbs are properly tuned and there are no carb holder leaks.

Ed

James027 wrote: ...I read the SM but don't wanna go through all the step of synching the carbs and all those adjustements without knowing it would fix my problems. I don't have much time to spend on this and I need the bike to go to work asap....

Could be helpful to first determine how far the carbs are out of sync.

Just hook sync hoses to the vac nipples and read the results.

Might already be perfect. -- Fat chance! :lol:

Good Fortune!

Hi, You were right about the vacuum leak Ed. I took the carbs out for the third time and notice that there look to be a leak by the carbs bowls gaskets. While I was there, I did the on bench carbs syncronization with 1/4" steel rod. I also removed the carbs holders and there was a good chance for a leak there too because of some old dried up sealant. I put everything back in place with permatex "right stuff" and the engine can idle around 1000 rpm's now. It was still running rough but I replace the points and set the timing with a timing light and it helped a lot.

I took a few shorts ride and it seem ok on the road but the bike wasn't starting so well. My main concern is that it takes some time before I can open the throttle (the engine dies if I only try to twist it a little). I connected a small bottle of gas to the #1 carbs holder so it can idle faster and finally be able to give throttle (and then go for a short ride).

I messed around with the pilot screws after reading that when warmed up, I should notice a change in rpm and make adjusments this way. But there was no noticeable changes and I think a messed up my pilot screw too much. Now the bike won't run over 5 seconds!! It start pretty good but die shortly after. Fuel suply is okay (I even did a test with a bottle to replace my tank) but nothing change.

Do you know another way to adjust those screws with the engine stopped? Mine are a bit worn out, is it so bad? Also do you have a file for the section of the service manual that talks about that (or maybe a link to a complete manual). I only have the manual for the 78 and up that use mixture screws.

That let me think that I got 2 set of carburators with mixture screws. They are dirty and need works (and probably parts) but are they better than the older carbs with pilot screws? Should I use them instead?

Thank you very much for your help!

Anybody can give me some infos on how to adjust pilot screws without the engine running?

Failure of noticeable change in rpm when pilot screw is turned usually indicates a dirty carb pilot circuit.

Here's one cleaning method.





Good Fortune!

Similar pilot circuit cleaning method may be used with mixture screw (based on correct understanding of the various pilot passages).

Objective -- with either pilot air screw or pilot mixture screw -- is to assure the fuel mixture enters the bore as it's supposed to (through the small orifice, or orifices, as the case may be).



Good Fortune!

Thank you very much Patton. I have those with bottom located pilot screw. I will take them off one more time and make a really good cleanup!!

Some pilot screws are worn out thought. I'll send some pics so you can tell me if I absolutly need to replace them.

Thank you!

Thank you. My KZ run way better now. I didn't know that there is actually 2 pilot jets. I cleaned those I saw the first time but when I unscrew them, I didn't look inside enough and unscrew the other one. I only blew air and that wasn't enough (even when I got them out, I had to use a needle to clean them). Two were totally clogged up so no surprise the engine wasn't running good.

Enough writing now. It's a beautiful evening to enjoy a long ride

Thank you!