Rough Idle

I just brought a 1976 KZ900 with 29 mm carbs on it. The guy I got the bike from filled the tank with gas and rode it to my house. He said that he had to keep messing with the idle screw to get it to run right. I could not get it to idle right and noticed that the #1 pipe was bright red. We took the carbs off and cleaned them. I put the carbs back on and turned the gas on before putting a inline filter on. I still cant get it to idle right. I sprayed carb cleaner where the carb connects to the rubber boot and it does not affect the idle. When I spray where the rubber boot connects to the engine, it caused the engine to either idle higher or it cuts out. Does the rubber carb holders need to be replaced ? Sorry for the long entry.

Kevin, I would say that you are on the right track. The carb boots tend to leak when they get old. A set of these ought to get you closer: www.z1enterprises.com/detail.aspx?ID=3245

Probably wouldn't hurt to check valve lash and spark to rule out any other sources for misfires.

I also noticed that when I pull the plug wires off of plug #2 or #3 I good a good shock. When I pull the wire off of #1 or #4 I dont. Could this be the coil since #1 and #4 are from the same coil ?

Sure could be. IIRC all of the tests for coils are simple resistance checks easily performed with a multimeter. Also you could remove the plug from the head,and leave the wire attached. Then lay the plug on the engine, and observe the spark while cranking. Should be a fat, blue spark.

How do I check to see if the coil is working correctly ?

Other than carbs, pretty much (98%)the same manual...

OEM FSM.... FREE!
kzrider.com/index.php?option=com_docman&...d&gid=434&Itemid=108

I took the carbs apart and found that the pilot jets were clogged. I cleaned all 4 of the pilet jets and the bike idled good. The next day it idled rough again. I took the pilot jets out and they were clogged again. How do I clean the carbs to keep the pilot jets from getting clogged again ?

check your filter, tank AND fuel lines, even if they're new, I had crap in my new fuel lines once causing problems

Check for rust inside your fuel tank. Rust sediment is the #1 issue with carb problems ! Either use POR50 or KREEM and coat the inside of the tank.

I just replaced the boots from the carbs to the engine last night and the bike was idling good. I started it today and noticed that the idle screw was not touching the lever on the carb at all. The bike would idle good and then shoot up to about 2500 - 3000 rpm. I could get it to idle back down to 1000 rpm by adjusting the air screws on the side of the carbs. Anyone have any ideas ?

BIGKEVIN wrote:

How do I check to see if the coil is working correctly ?

have somebody else pull the plug wire off! :woohoo:

If the timing is not correct, can that cause the idle to surge ?