Carb help

[RRS_07RdStar]

Install the dj pilot and see if it helps. If not install a Mikuni 37.5 pilot. I'd be curious to know. As Said I would never put out that type of info based on my assumption, It was from research and talking to DJ tech support to obtain that info. I guess the only assumption on my part was assuming that the tech support guy knew what he was talking about. lol

Also there should only be 1 washer Under the clip. Putting 2 under the clip only richens the fuel mixture at cruising speed by about a 1/2 groove on an adjustable needle. In the stock configuration the cruising speed AFR does not need to be richened at all. The 2nd washer should be placed on top of the clip for the little spring to set on.

I finally got around to installing DJ 37 pilot jet. I also removed 1 of the washers from under the needle clip and placed it on top. I had the PMS screw out 3.5 turns with the Mikuni 35, I took a guess and moved it back to 2-3/4 turns for initial setting. I tried starting the bike with the enrichener in (running position) to check if pilot circuit might be to rich, but wouldn't start. I pulled out the enrichener, and it started right up. I was going to take it for a long test run, but I got a mile or 2 away and it started pouring, so I turned around and came back. I had let it warm up enough before I left, and I think it's really close to where it needs to be, no hesitation, blipping throttle seemed crisp, and bike seemed to accelerate nicely. Throttle returned to idle quickly when letting off. I have to check the idle rpm, may try turning PMS back another 1/4-1/2 a turn to see how it compares, than take it for a longer run to verify it running well.

I did take measurements of all the holes in both Mikuni and DJ jets for comparison. I have full set number drills to #80. I used the shank end of bits to test until I found one that fit snugly and the next size wouldn't fit. One thing I noticed, and I ran into this recently on aftermarket jets for a 72 Honda CB500 I recently restored, the DJ jet didn't do a good job of cleaning burrs off the back of holes. When I was trying to measure the id of the emulsion end of the DJ pilot, there were burrs on the back of some of the 8 perpendicular through holes. I had to use the drill end to clean the burrs off. The Mikuni jet was well machined with all sharp edges de-burred and the 8 holes on emulsion are chamfered (see attachment) . Keeping all holes clean from burrs will give the max flow it can. Burrs obviously can impede the flow. Anyway if you want dimensions, I can give them to you, I just didn't want to give you my scribble, I'd make a little nicer sketch.

[Jokke75]

I put a follow up question here: for my 2003 XV1600 I have K&N airbox and plan to go for Cobra HP 2-1, carb is stock now. I have Barons jet kit coming + plus mikuni 37,5 pilot jet on top. Shall I go with 167,5 main, the 37,5 pilot and clip on the 4th groove in Barons needle, PMS 2,5 turns out? This is what I’m picking up here but would that fit with the K&N - Cobra -combo?

Any other tips / things I should consider? Many thanks!!

[davej]

yes that will be the jetting for your bike with those mods. You may have to play with the PMS just a little with the weather being colder this time of year. you may need to turn it out 1/4 turn or so

[Jokke75]

Thanks, davej, yes it’s off season for us here now...garage months ahead and back out riding hopefully in April again. (Yes, we know, the weather here in Nordics suck!

[Rsnewbie92]

Hello all. I have a 2003 road star 1600 and the fuel pump shit out on me and decided to go pumpless. Replace float needle and removed filters from carb fuel line and petcock. Rode fine for 3 miles and started acting like it was starving for fuel and starts sputtering hard. What could I be missing? Also noticed main jet moves up and down, Is that normal?

[Duke]

NO! The main jet doesn't move, if it is, you might be missing a collar that goes on before the main jet

[Father Pobasturd]

I don't think jets are supposed to move. Routing of the fuel line may have something to do with your issue, but I would see if you can tighten that jet first. Did you vent the gas cap or remove the roll over valve? If it starves again, shut it off and open the gas cap. If air comes out you have a venting problem. I've been pumpless 6 years and have no regrets.

[Rsnewbie92]

I vented the cap and it seemed to help but when I get on it hard it still stumbles some. The tube that the main screw into moves up and down freely and I’m about to remove the carb and check everything again.

[Duke]

With all the tuning, using jets and needle, there are some other ways to help the tune by working with the emulation tube and the jetted air feed for that main circuit. This tuning area is complex and can be messed up easily.
If your bike is running great with great fuel mileage, but has a stumble when increasing the throttle, then after checking the accelerator timing, if ok, then this is where I would work with the emulsion area to help bring main circuit fuel into the carb throat at the right time. This stumble would be caused by a momentary lean condition, and that's where you need to richen it up, "during the high vacuum signal".
This is food for thoughts. Every engine is slightly different, and to do a good tune, a lot of dialing-in has to take place. Standard setting are great, but to really tune-in a carburetor, tweaking and adjustments are needed for the mating of carb to engine.

[Darkwingduck]

Could a faulty Rectifier cause a misfire when hard throttling? Hard acceleration, occasional misfire (pop)w/slight hesitation, from exhaust while picking up speed. It seems to be in lower gears and infrequent. Had a short in the electrical at three plug connectors. Old dry casing on wires had peeled and caused a short. Fixed wires, and tested all components for damage with resistance and ground and open loop testing. all was in parameters except for the resistance on the New stator I had installed about a year back. The resistance read within guidelines I got here off the clinic, but fell slightly shy of Clymer Manual specs. I've aside from a carb cleaning, I've got here running great. Ive gone thru all the recommended carb adjustments I could find on the Clinic, just this one problem keeps happening.

[Duke]

Low voltage could cause a ignition problems, but doubtful as what you are saying. If you followed the advice that has been given in this post, and doing it correctly, then you could check out the emulsion tube. once you mess with that tube, there is no going back! Opening the second from the bottom 2 holes up another .002" in the emulsion tube, will momentarily help bring a richer signal when throttling up.

[Shotround]

is the accel pump timing a common adjustment? from riding and confirmation with the afr guage, it seems mine needs to start earlier, esp when the bike hasnt fully warmed up. by warm, with enrichener out for 3-5 mins in driveway and the half mile out of the neighborhood. after that i push the knob back. ive always wondered if this was the cause of it being 'cold-blooded'.

i need a bit more food. my thinking gears have seized up and possibly disintegrated.

[Duke]

Adjustments to the accelerator pump timing should be done for good tuning. I've found that if you get a very-very slight stumble when accelerating the throttle wide open in neutral, then that's where I set it to. When you are in gear, going down the road, you won't get any stumble.