Author Topic: B12 1G jetting question (Read 2961 times)

Nitro · « **on:** June 09, 2007, 07:26:08 PM »

I wanted to replace the fuel line today, since it is spliced with a piece of copper tubing (just bought the bike about 5 or 6 weeks ago). In order to get the fuel line loose at the carbs, I had to remove them completely. I checked to see if it had been jetted. The adjustment screw covers have been removed and the jet needles have clips with 6 slots for the c-clips. The one I removed has the clip in the 2nd slot from the top, then a plastic spacer, and a thin washer. The needles have no visible taper. Am I correct in assuming (from reading other posts) that these are Ivan needles, or maybe (shudder) Dynojet? My bike doesn't have any major carburetion problem, no noticeable flat spots. But, around 1500-2000 rpms (around town speed limit is 25mph) there is a little surging. Would adjusting the pilot screws and/or moving the clip down a notch help this any or should I leave them be? Does screwing the pilot screws in make the idle leaner or richer? The exhaust is still factory, and the filter is a K & N. Oh, the float bowl screws aren't allen head, so it isn't a Holeshot kit.

Thanks.

okbandit · « **Reply #1 on:** June 09, 2007, 11:39:14 PM »

Sounds like a dynojet to me. The ivan's needles are tapered as are the holeshot's. The surge you have is at an extremely low rpm. Most b-12 riders never ride that low in the rpm range so just avoiding it is the easy fix, but as long as we are talking about it..... A/F screws are for idle and very light throttle loads, out is richer (the cure for surge) mid range rpm and larger throttle input is needle and clip lower is richer. My advice if you want to cruise in that rpm range is back the A/F srews out 1/4 turn and test until it goes away, but make sure you keep track of where you start in case things get worse so you can go back. I cruise at a minimum of 2500rpm.

Nitro · « **Reply #2 on:** June 10, 2007, 12:53:21 AM »

OK, I'll try that. I just don't like riding around at 25mph doing 3000 rpms in second gear.

Red01 · « **Reply #3 on:** June 10, 2007, 12:54:50 AM »

Why not? You've still got 7000 to spare.

Nitro · « **Reply #4 on:** June 10, 2007, 02:59:38 AM »

It just seems like overkill. There's plenty of torque at 2000.

Banditmax · « **Reply #5 on:** June 11, 2007, 07:28:33 AM »

Jut go 30 in third lol

Nitro · « **Reply #6 on:** June 29, 2007, 07:33:18 PM »

OK, I turned the idle adjustment screws out 1/4 turn. That made it worse. So I closed them 1/2 turn (3 turns out), and that is a little better, but it still surges at steady speeds between 1500 and 2500. I tried with them further in, but it slowed down the idle speed, so I'm thinking they're as close as they are going to get. At what rpm do the needles begin to have an effect? I'm thinking of moving them up a notch. I realize that the idle circuit (low openings) and the needle jets/needles (mid range slide openings) affect each other at a certain range of slide opening. Oh, by the way, I'm getting 35 to 41 mpg, so I'm guessing it's not running real rich.

okbandit · « **Reply #7 on:** July 01, 2007, 11:42:25 AM »

Transition is complex. At small throttle openings you are using the A/F screw settings, the needle position, and the mains. Transition begins around 2k at WOT but varies at any other throttle. Raising the needles would be a good experiment and costs nothing but time.

Nitro · « **Reply #8 on:** July 01, 2007, 06:12:03 PM »

OK, I have new plugs to install, so I'll raise the needles a notch when I do that.

Thanks.

roogazza · « **Reply #9 on:** July 01, 2007, 06:34:40 PM »

Don't be afraid of Dynojet Kits, mine Carburates perfectly and flys. From the day I fitted it with the instructions I only raised the needles 1 clip to suit my bike and I'm rapt with the result. Gaz.