JRC 30mm carbs

Just picked up a set of these from Steadfast. They work pretty good but for the life of me I can't get a consistent idle except for a short period of time. checked for intake leaks.
The one thing I noticed is that just as the slack in the cables is taken up and the slide starts to lift, the idle speed will go down momentarily.
Here's my setup
138 main
38 pilot
needle 2nd from top
mixture screw 1 1/2 out

Anyone have any success with getting these to idle right?

You say you have the mixture screw 1 1/2 turns out. I assume that this is the best possible setting with the turning of the screws in either direction will cause faltering?

How are you turning the right side mixing screw which I think would be tight between the carbs? And the throttle stop on the other carb, for that matter? These require active and dynamic (motor running) adjusting. Having to pull the carb to give it a 1/4 turn one way or the other does not sound inviting. My carbs came from JSMotorsport who did some modifying for this situation.

What do the plugs look like after idle for a spell?

I have 32's and i have found them to be inconsistent or perhaps rather sensitive. i have a 40 pilot in one and a 35 in the other. I have heard other using this setup as well.

Have you added a balance tube?

How are you routing you fuel lines? I found that to be a little strange as well. If you don't loop them around each other, they may crimp trying to run them through tight places. I had trouble getting over 85mph for a while untill I ran the lines proper.

Not knowing your level of experience with tuning these things(amal included) the process of balancing and syncing these up can be frustrating at first. This frustration will subside over time. Feeling and listening at the exhaust along with plug inspection will help narrowing this to satisfaction.

Throttle stops and cable adjustment need to be right on as well.

Sorry if i assume you do not know much but we can only go by what you offer us.

Enjoy!

If you have too little play in the cables, any movement in the bike can slightly alter the idle. You might want to put a bunch of slack in the cable, and then tighten after you get an idle. At least it eliminates one potential problem.

I've tried 11/4 & 1 1/2 turns out simply because of the hassle you mentioned getting at the idle mix screw. Fuel lines are not kinked or obstructed in any way. I run 2 Tee's bridged to each carb...1/4 inch hose. Cables have 1/8 free play. Balance tube is as stock. I have quite a bit of experience working on Brit bikes. My 79 Bonneville has no issues whatsoever with the JRC's. It is my understanding that there is perhaps a specific needle for a Norton application?

Snakepit said:

I've tried 11/4 & 1 1/2 turns out simply because of the hassle you mentioned getting at the idle mix screw. Fuel lines are not kinked or obstructed in any way. I run 2 Tee's bridged to each carb...1/4 inch hose. Cables have 1/8 free play. Balance tube is as stock. I have quite a bit of experience working on Brit bikes. My 79 Bonneville has no issues whatsoever with the JRC's. It is my understanding that there is perhaps a specific needle for a Norton application?

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Check with Jim at JSMotorsport. He should be able to set you up.
http://www.jsmotorsport.com/

I made a little tool that allows me access to the inner mixture screw. Seems better at 2 1/2 turns so I'll try that for a bit.
Off the subject...did you do the holes on your primary (looks good). I put a sealed clutch bearing in mine and want to run the primary dry ...so that must help keep things a little cooler?

Snakepit said:

I made a little tool that allows me access to the inner mixture screw. Seems better at 2 1/2 turns so I'll try that for a bit.
Off the subject...did you do the holes on your primary (looks good). I put a sealed clutch bearing in mine and want to run the primary dry ...so that must help keep things a little cooler?

Click to expand...

***ALERT*** ***ALERT*** ***ALERT***
If you run a chain you need to run lube in there. Type F ATF till it drips out the level hole while on the side stand. The clutch was never meant to be wet, it just gets that way.
Again, unless you have a belt drive, run lube. It's just for the chain now that you have the sealed bearing.

Yes, I drew up a pattern, taped it on, center punched it and drilled it. It's spaced and graduated for a 1/4", 5/16", and 3/8" drills.

It sounds a bit rich at Idle.
Will it Idle long enough to get a colour reading off the plugs.
If raising the slides slightly, ( adding more air ) and or turning the Air screw out ( adding more air ) helps
then it sounds rich.
I know it's not " written law " but 30mm carbs of the same brand should theoretically use Pilot jets about .5 smaller than
32mm carbs... ish. As per PVs.
I have zero experience with this brand of carb, so I should just keep my big nose out, but they're all pretty much the same.