KZ750 Spectre - Running, but only on two cylinders.

Hey yall. I just got my bike running, but its not running right. The throttle hangs up and it dies while running. I took a laser thermometer and cylinders 3 and 4 are getting hot, but cylinders 1 and 2 are not. There is also hardly and pressure out the pipes of 1 and 2. I'm getting great spark and all the carburetors have been freshly rebuilt. And ideas or recommendations to check first?

If #3 & # 4 are getting hot , then its not the coils. You have a problem either with the lead wire, spark plugs or connectors. Try cutting a bit off ( 1/8 ") the lead wire at both ends and reconnect, check spark plugs as well, hopefully that is it.

Could still be carbs, too. Were they synchronized on the bench before installation? Were they vacuum synchronized on the bike? Was the fuel level confirmed in each carburetor using the clear tube method? Were the coils hooked up to the wrong sparkplugs? Valve lash within the specified range?

Yes TexasKZ, it´s every time the same story on every bike/engine/carb rebuild.
Some little Gremlins get a new home.....

Scirocco wrote: Yes TexasKZ, it´s every time the same story on every bike/engine/carb rebuild.
Some little Gremlin gets a new home.....

Sneaky little devils.........

It has been benched synced, but not vacuum synced yet. But they still should at least run a little correct? I'll have to try the clear tube method, do I just put the petcock on prime and let it fill? I have not checked valve lash as I have never done that before, can that be done easily?

mopguy wrote: If #3 & # 4 are getting hot , then its not the coils. You have a problem either with the lead wire, spark plugs or connectors. Try cutting a bit off ( 1/8 ") the lead wire at both ends and reconnect, check spark plugs as well, hopefully that is it.

I'm getting nice fat spark to all cylinders sadly

This reminds me of an carb rebuild some days ago here on KZR where the float was installed upside down. Same symptoms (Gremlins???):whistle: :whistle: :whistle:

When you rebuild the carbs did you remove the pilot screws, bleed pipes, pilot jets, etc and make sure all the passages and jets are clear? The orifice in the bleed pipe and pilot jet are very small and you need to hold them up to the light to be sure if they are properly clean.

If the carbs are badly out of sync, it won't affect cylinders firing. I would check to see if there is gas in those bowls. If there is, the problem may lie in compression (valve clearances) or electrical. Make sure the plug wires are going to the right plugs and check for spark on the cylinders not firing.

Nessism wrote: When you rebuild the carbs did you remove the pilot screws, bleed pipes, pilot jets, etc and make sure all the passages and jets are clear? The orifice in the bleed pipe and pilot jet are very small and you need to hold them up to the light to be sure if they are properly clean.

EVERYTHING was removed from the carburetor, I soaked all of them in carb cleaner. I then replaced all jets and needles making sure they were sized properly.

wiredgeorge wrote: If the carbs are badly out of sync, it won't affect cylinders firing. I would check to see if there is gas in those bowls. If there is, the problem may lie in compression (valve clearances) or electrical. Make sure the plug wires are going to the right plugs and check for spark on the cylinders not firing.

The bowls have gas, and I have good spark to all cylinders. Going to do the bowl level trick tomorrow hopefully.