Help! High Idle when bike warmed

[thach1130]

I fiddle with the throttle bodies sync and now the bike is much smoother than before. However another problem has arisen. The bike idle higher than usually. Seems fine when the bike first started seems to hover around 1400rpm but after some riding and coming to a red light with clutch in and in first gear the bike idle around 1800 sometime 2000rpm. Slight release of the clutch and grabbing it again will lower the idle to 1500 but then slow creep back up.

I will adjust the idle tomorrow but don't want to lower it too much that it will not be enough when i first start the bike.

Anything else i should pay attention to?

One other source it could be is the PCV. Maybe i need to perform the throttle calibration again.

 

[TorontoAlex]

Just a wild guess. How does it act when you're in neutral? May be the clutch or clutch springs. Clutch is always engaged a bit even when pulled in tight.

 

[thach1130]

When first started up idle around 1500rpm. After bike warms and pulling up to a red light holding in the clutch it linger around 1800-2000 rpm

 

[DanS]

Idle speed should be 1150 to 1250 rpm's with the engine warm. Syncing the TB's can effect idle speed. Did you let the engine warm up and adjust idle speed as you were syncing the TB's?

 

[thach1130]

Yeah, i waited a little bit until the engine warmed up.

Used this tutorial to start fresh. I went with 2 and 1/4 turn out from complete close. I found at that point the throttle bodies were almost perfectly in sync at idle. Then i proceed to adjust it at 4500rpm, the range which i normally cruise at. Bike is immensely smoother now. But now i have that idle issue. I didn't see any problem at the time of the adjustment. It's when i had bolt everything back up and took a ride to work. The 8 miles i traveled i notice at every red light the bike was idling at the higher rpm. At first i thought it was my throttle cable slack adjustment. I thought i didn't give enough slack and it was constantly engage. Adjust the slack to give a little and still have the issue.

Maybe the throttle bodies are so in sync they rev easier and have a higher idle rpm. LOL. Rained today but i will definitely attempt to adjust the idle tomorrow with the idle adjustment.

 

[9 Lives]

Unfortunately there is a lot of misinformation on these forums. The link you posted is for a different bike and not applicable to this one. I would suggest you only use information from a reliable source, like the shop manual or a local dealership mechanic. There is no TB sync at 4000 RPM only at idle, the 4 brass screws adjust the air at idle only they are not designed to adjust anything else. The more the butterfly valves move off the idle position the less effect the brass screws have. By the time the bike is at 4000 rpm the butterfly are way off the idle position and you have to turn the screws alot more to make a difference in vacuum reading which will completely knock off your setting at idle. There is a sync at 4000 rpm on some older carburetor bikes but not this one. Again to save your self some headaches use the Shop Manual, you can download it for $14, it will be the best money you spend if you plan on doing your own maintenance.

 

[thach1130]

I see. I do have the service manual. That link was a guy synchronizing his FZ1. I figure they are similar enough. I'll readjust to be smooth at idle then.

 

[9 Lives]

I see. I do have the service manual. That link was a guy synchronizing his FZ1. I figure they are similar enough. I'll readjust to be smooth at idle then.

The FZ1 has different throttle bodies that the FZ8, the only adjustment on the FZ8 is the idle air, the butterfly valves are on a solid shaft and not adjustable.

 

[thach1130]

I've resync it to be even at idle. I've also adjust the idle to the proper range of 1150-1250. Thank you for all the inputs.