Topic: High Idle Problem CB750 K7

[mkoski]

Hey guys,

Here's an interesting one I cant figure out. My idle is too high when my bike is warm. I'm running PD41A carbs, pod filters, 4-1 motogpwerks pipe, stock idle jet, main of 125.

My idle stop screw is not in contact with the plate on the throttle linkage rod so I have no ability to adjust idle RPM with this mechanism.

Any way to lower idle rpm in a reasonable way? Everything is perfectly tuned as per spec/common sense with pods, just need to synch the carbs is all that remains.

Wasnt ever a problem last season while riding and I have no idea how to bring it down so I can adjust RPM with the screw as intended.

Also note, the idle isnt crazy high, either, just a bit fast. I also do not have a tach installed impairing my ability to give a specific RPM.

Thanks,

MJK

[flybox1]

I bet if you looked thru your carbs with a backlight, you'd see #2 all the way closed, and 1,3 & 4 hanging open just a little.
makes it difficult to lower an idle when slides are at different levels
complete your vacuum sync, and report back...

[mkoski]

That was the only thing I could think of and they are all the exact same visually. (Which may mean FA). I'll do just that, I figured that would be the response!

I was hoping it was something obvious I missed. I'll synch and report back.

[LesterPiglet]

Syncing the carbs will allow you to put the idle screw back to it's proper position. Lot's of detail on lots of other threads...do a search.

[flybox1]

That was the only thing I could think of and they are all the exact same visually. (Which may mean FA). I'll do just that, I figured that would be the response!

I was hoping it was something obvious I missed. I'll synch and report back.

you'll notice when you sync, and make TINY adjustments on the vac sync screws, you can get BIG changes in vacuum   

[mkoski]

That was the only thing I could think of and they are all the exact same visually. (Which may mean FA). I'll do just that, I figured that would be the response!

I was hoping it was something obvious I missed. I'll synch and report back.

you'll notice when you sync, and make TINY adjustments on the vac sync screws, you can get BIG changes in vacuum   

Good to know! I have been reading up on this and was wondering what to expect. I'm just waiting to get a set of gauges. How much of an improvement can I expect from a synch in terms of smoothness, valve noise reduction? Dramatic or so-so?

[flybox1]

smoother, lower idle
less noise/top end chatter
snappier throttle response
better gas mileage
more even operating temps across the head