| Author | Message | ||
     Deanh8 |
I got a used mikuni off a big bike that im going to make work. Didnt pay anything for it, but I have no idea where to start off with the jets. Bike has a V&H muffler, forcewinder and thats it. What should I put in there before I even put it on the bike? | ||
| Ebutch |
http://www.mikuni.com/fs-tuning_guide.html | ||
| Fahren |
What bike? Your profile only shows the XB. | ||
| Deanh8 |
Sorry this is going on my other bike. 2000 M2 | ||
| Sanchez |
NHRS recommended starting with a #30 pilot, a #165 main, and the standard needle with the clip in the middle position. My bike has a 1250 kit on it, though, so YMMV. My S1 came with a 22.5, a 160, and a -96 needle (one step richer) with the clip in the 2nd notch from the bottom (one notch richer). I went through various permutations to try and get it running right, only to ultimately discover I had a leaking intake manifold seal. So as it sits now, it has a 25 pilot, a 165 main, and a -96 needle (one step rich) with the clip in the middle position. The pilot is too small because I can turn the air screw in to about 3/4 before the motor stumbles. I'll probably also go back to the -97 (standard) needle now that I'm not trying to compensate for extra air coming into the motor from the intake seal as well. My fuel economy was poor on the last tank, but i need to run another one through to see if that's owing to the needle or just to my wrist.  | ||
| Ztferrari |
running a 27.5 pilot. -97 needle (forget what clip position, i think richer than std, and a 180 main I have edelbrock heads, cams, and ignition for reference on my s2 | ||
| Sanchez |
I observed 3 problems: - Crappy gas mileage (~36 mpg) - Some pinging at throttle opening in high gear/low speed - Air screw too far in before the motor would stumble (3/4 turn out) Normally I'd only change one thing at a time, but all three symptoms have different tuning parameters that Mikuni says don't relate to each other. So I changed three things last night: - Changed to a -97 needle (the "normal" needle) vs the one I had, which was one step rich. Should improve fuel economy. - Put the new needle in with the collar one step down. Should give me more fuel right at the beginning of the throttle opening. - Stepped up from 25 to 27.5 pilot. I took it out for a short test run this morning, and it seems to be running nicely. I couldn't get it to ping rolling on the throttle in 5th gear at low RPM. The engine now starts to stumble with the air screw at 1.5 turns as it should be, and it's idling great at 2 turns out. Time will tell if the pinging stays gone when the motor's really hot, and hopefully I'll get more than 100 miles out of this tank of gas. | ||
| Homebrewed1 |
I have a NRHS 1250 kit on my 1999 S3 Thunderbolt. It has XB heads, stock cams, race computer (for ignition only now). I switched from fuel injection to a Mikuni HRS-42 back in the spring, and it was the best move I ever made to the bike as far as rid-ability. I have the pilot at 27.5, the main at either 160 or 162.5 (cannot remember the final) and the standard needle in the standard position (as it comes in the box) which I think is the middle setting. My guess is a 25 pilot, a 150 or 155 main should work on a stock engine as a starting point. Buy main jets from 150 to 165 and have them on hand for tuning. I think the pilot will be spot on though. You could always get a 27.5 just to have on hand in case you need it though. Check with Dan at NRHS if you want any other starting points, but that should be in the ball park for you. |
