I have removed the fuel pump on my 2000 R* Project . I have also put some Rhinehart Short staggard pipes with baffles on it and it has a Baron's Big air kit . I changed out the Needle Valve and I have tried multiple Main Jets anywhere from 167.5 up to 180 Makuni, and multiple Pilot Jets (35, 37.5, and 40) I keep getting a backfire from the rear pipe (actual flame coming from the rear exhaust) on the bike stand from idle up to maybe 1/4 throttle and no amount of adjusting on the PMS will make it completely go away. It will get better and worse, but never gone. I checked for leaks and as far as I can tell both the exhaust and the manifold are fine. I checked the plugs and the front look fine while the rear look rich. By the way, I'm in San Diego, so I'm pretty much at sea level.

So my next step (and I know it should have been my 1st step) was to check my float bowl setting. After reading multiple articles on the forum I thought I was going in pretty prepared, but the more I try to adjust it the more confused I get. The manual says to adjust it to 4 or 5mm above the float bowl mating surface, tech articles say anything from 1-2mm above to 1-2mm below the mating surface. Here comes my main question: Which mating surface are we checking against? The manifold side is like 11 or 12mm higher than the air cleaner side.

When I started this little expedition my float bowl level was at 7mm above the mating surface on the air cleaner side. Should I be higher or lower than that? And I just gotta add that that little adjustment tang is one sensitive little bugger!

Thanks in advance for any suggestions.

Teal

did ya remove the AIS, if not, then get it off. float bowl is measured at the rear of cab (manifold side)
The amount of air that the ais dumps into the exhaust to help burn unused hydrocarbons is too much for after market pipes. Friend had the same issues, flames, that was after we did jetting, he forgot to bring the plugs for ais removal, next day took ais off and all was fine

Oh yeah, I forgot to mention that the AIS is long gone.

flames is certainly not a good sign, sounds like a leak somewhere and it would have to be a rather big leak if a 40 pilot jet didn't even compensate with using the Barons needle. where is the clip on the needle, counting from blunt end? and you did use the spacer and washer on it as well? Most I know have it on the 4th groove spacer 1 washer or 3rd groove spacer 2 washers. You did put a cap on the manifold vacuum port? What did ya use to look for leaks at the manifold? my preference is starter fluid since it is very volatile and will find the smallest of leaks. I could never find a leak with wd40. for the exhaust, a smoke test usually will find leaks, that is if you have a garage to do it in, cigar, cigarette, even incense will work for a smoke test

OK, First off thanks so much for your help so far Erbman....I finally got the float set. Man what a pain!!

I can get the backfireing to stop if I back the PMS way out, like 6 or 7 turns. I'm guessing that I will need to go to a different Pilot Jet now. Any suggestions. Right now I have the needle set a 3rd groove-spacer-2 washers, 170 main and 35 pilot.

Like Erbman said - looking at the carburetor check the level on the left side at the back of the carburetor. There are 2 different level specs - one with the carburetor off the bike and level on the bench and that spec is 2-3 mm below the bowl flange seam. The second is with the bike level and the carb mounted on the bike and that spec is 4-5 mm above the seam.

What your describing sounds like maybe the rear cylinder is misfiring. If the rear plugs look rich then combustion isn't complete and when the cylinder fires it reignites the unburned gas in the exhaust. Looks like you need to find out what's happening in the rear cylinder. Maybe only one of the plugs is firing. Just a thought.

Scott B.

So after getting the float set, I was able to get the backfiring to stop, but the PMS was out way too much. I put in a 37.5 Pilot jet thinking that it would bring the PMS back in. It didn't.

What really confuses me now is that my 35 pilot is bigger than my 37.5 and my 40 is smaller still. Do the numbers go backwards on these pilot jets? Is it possible to drill them out to make them a little bigger? I don't have any other Pilot jets.

the bigger the # the richer, even with DJ jets. Are these mikuni jets? all Mikuni jets have a box in a box logo stamped on them, if it doesn't then it's not a Mikuni. and using the Barons needle and a BAK air filter you shouldn't need anything larger than the stock 35 pilot. suggestion, put the 35 pilot in, set the pilot screw out 2, 2.25 turns out from a light seat, take a ride to properly warm the engine, trying to warm the engine at idle is not enough, once you get the engine warmed, adjust the idle knob. very could well be that the idle is not adjusted correctly, if it's set too slow, the pilot screw adjustment doesn't do enough to bring it up to speed. look at it as the idle screw is a coarse adjustment, and the pilot screw as a fine adjustment. Need to get the coarse in range, then fine tune. seems a lot get focused on the pilot screw and forget about the idle control