High revving idle

[billdn]

Finally got timing sorted on rebuilt engine and couldn't resist little shakedown ride, you know how it is ! Gearbox smooth, clutch needs adjustment but easy to do.
However despite setting idle screw at 1200rpm , albeit bit lumpy, went well. Until I had to stop at junction   revs hit 3000rpm with throttle closed and undone idle screw so wasn't touching , confusing 😐!
Otherwise rode lovely but obviously needs sorting, even rolling off throttle didn't lower revs  then slowly eased off.
I'm guessing balance carbs? They have been stripped ,  cleaned new o rings, courtesy of Nurse Julie, and replaced brass rod for carb floats. Float heights reset to 21mm too. Am I right about balancing  please don't tell me got to take damn things off again 😒

[Oddjob]

You may not have enough slack in the pull cable Bill. Have you tried loosening that off as well.

[K2-K6]

You probably need to reset the carbs with Bryan's method to get a parity of components before refitting.   

In situ, lower all the slides an equal amount and then it should start to sit with the main idle speed adjustment more realistically located to give competent adjustment. Rough and ready but should move you in the right direction.

The cause is usually that the sllides have been set during assembly too high, such that with the lifter mech bottomed out the slides still don't close off the venturi.

Don't worry, it's very often done and reasonably easy to work your way out of it.

[Nurse Julie]

Well done for getting her back on the road Bill. It does sound like a bench sync is needed.

[TrickyMicky]

I agree with Oddjob, before diving in deep with all the strip down malarky, look at the simp-le stuff first. The push pull cables do take a couple of minutes to set up, plus check that they are routed correctly especially round the headstock and right fork, and check engine reaction when turning the bars from lock to lock.

[Sesman]

Disconnect the cables, unscrew the idle screw until it doesn’t touch and manually flip the throttle arm. If the arm snaps back freely the intial set up is the problem. Make sure those idle jets and carb drillings are completely clear too.

[andut]

Check the choke lever’s fast idle adjustment also.  I had a similar experience on the shake down of my 400 and I hadn’t tightened the lock nut on the fast idle setting.

[billdn]

I agree with Oddjob, before diving in deep with all the strip down malarky, look at the simp-le stuff first. The push pull cables do take a couple of minutes to set up, plus check that they are routed correctly especially round the headstock and right fork, and check engine reaction when turning the bars from lock to lock.

Good idea, with cables disconnected, sliders snap back closed easily but just can't get cable routing right. Don't suppose anyone has pic of routes for theirs - I've seen the diagram but to be honest it's not that clear. Do they run through headlight bracket or behind it, note to self ALWAYS take more pics of everything before you start!

[Sesman]

If the sliders snap back with cable disconnected, try starting the bike. If the high idle is still present with the tickover over screw fully out, you need to remove the carbs and check the throttle slider heights. The procedure is very straight forward.

[Sesman]

Try this.

[billdn]

Well done for getting her back on the road Bill. It does sound like a bench sync is needed.

Thanks Julie,
I did follow Bryanj's method as well and your flot setting method too- so must be one of your two's fault, as I never do anything wrong 😇🤣😂

[billdn]

Okay so carbs off ..again! To attempt bench sync a la Bryanj method, what could be easier 🤔.  So found lowest slider and adjusted gap for drill bit, using 1.5mm bit. But when trying to use separate adjusters for other carbs there is no further adjustment available to achieve same gap?  Have I missed something when reassembled carbs after cleaning?

[K2-K6]

Start by screwing the main adjuster for carb rack tickover inward to lift all slides before anything else.

Then set the slides.

You've got to be able to lower that tickover adjuster after synchronisation to drop all slides back downward that drill size (1.5mm ?) before you can run them.

You need AT LEAST the 1.5mm lift for that first step in the screw range, plus some more to make sure you don't run out of thread when in use on that screw.

Bryan described it well, but follow the instructions to the absolute letter else important bits will be missed.

[Sesman]

Unscrew the main idle adjuster until it no longer touches the adjuster stop. Pick a carb, any carb, and adjust the slide adjuster until the slide bottoms out. Lock it off. Now use the main idle adjuster to lift that slider until you achieve a sliding fit. Now use the slide adjusters on the remaining slides to get the sliding fit without touching the main adjuster screw, you are good to go. You are approaching the slides from the engine side and not the airbox side?

[billdn]

I wasn't knocking Bryan's method, it's just I felt like I was doing something wrong, I'll give a good read and tackle it in the morning,  when I'm less inclined to fling it across the workshop.