Idle speed drops w/slight throttle pressure

Finally have the jrc carbs dialed in on my '72. Only issue is idle. With my hand off the throttle the bike idles smoothly. If I just apply minimal pressure to the throttle, not opening it, the idle drops dramatically but doesn't die. I can hear the slides hit their stops w/the motor off. Any thoughts? Thanx, Rick

Well when the slides are resting on the idle screw tip and are pressed on by the springs they then cock away from their support. Now when you change this by supporting the slide buy the cable the slide un-cocks as a first response. If this action provides more or less air then it would effect the idle. The slides do need some slop or they would stick. If it's bothersome I would put a set of carb sticks under the slides and check to see if the slides are working in unison perfectly. Or are you running this as a single carb conversion? One could also use fingers to partially block the air flow at the key moment to see if the lower idle is from too much air or too little and work from that knowledge to correct the problem.

Carbs could be out of balance eg slides not sync'd, mine goes that way too. At small throttle openings the difference between 2 out of sync slides is at its greatest, at WOT its virtually nil.

This is if you have 2 carbs, if you have one then look at the JRC eqivalent of the slide cutaway.

2 carbs. The sync looks good w/the drills under the slide. I'll check it again. I just happened to notice it by accident actually and there's no affect adversely on acceleration. It would have taken me a while to figure out the cocked slide bit. Thanks

You could try holding the throttle open just to the slow bit and twiddling the mixture screws for best running. That might at least tell you if it's rich or weak and which carb is doing it, if not both.

This is going to be an air screw thing rather than a throttle stop thing. As with any duel setup, Mikuni's and jrc's are going to be much fussier than amal's. I have heard of people giving up with trying to get any duel setup to sync up other than amal's. Initial throttle responce can be the last straw in your patience level. High performance carbs may need special tools to get sync'ed. Not much help but maybe some insite.

It sounds like fuel air ratio is slightly off.
More air at initial opening and fuels not sufficient.
Can you change to the next size larger pilot jet with JRC's?
This might cure the stumble. My Amal's do this when the slides are ot of synch.
My pilot screw is removable and can be swapped out.
I'm not sure if the pressed in bush pilot was reemed out or enlarged and a removable
inserted underside in place? It works so I'm leaving it.
The stumble of the idle at throttle movement sure sounds like a fuel/air ratio issue.
Marshal

What size are these JRC's. Could be just not enough venturi for these to work.