I have a 2004 R* that I bought used from the original owner with Freedom Racing duals and a BAK. He said he had a shop set up the jetting for the intake/exhaust, but it had a stumble right off idle that suggested a too-small pilot jet.

So I opened up the carb and found a 35 pilot jet, which I swapped out to a 37.5. (Haven't had the chance to try it out yet, but it certainly started better cold with less choke.)

The main jet says 195, which must be Dyno because I don't think the Mikuni jets even go that high? Even so, a 195 Dyno translates to something bigger than a 180 Mikuni. Does that seem a bit high for an otherwise unmodified engine? Does that suggest perhaps a larger needle was used? If so, how do I tell?

Before I changed the pilot it ran well at higher throttle settings, but had a stumble off-idle which was worse in cold weather and especially in cross-winds from the right - which was apparently a ram-air effect. I'm hoping the larger pilot corrects this and I don't need to open up the carb again.

BTW, how many turns on the PMS would you start with? I have it at 2.5, which seems like it might be too rich given how well it started cold...

twowheelsgood wrote:
I have a 2004 R* that I bought used from the original owner with Freedom Racing duals and a BAK. He said he had a shop set up the jetting for the intake/exhaust, but it had a stumble right off idle that suggested a too-small pilot jet.

So I opened up the carb and found a 135 pilot jet, which I swapped out to a 137.5. (Haven't had the chance to try it out yet, but it certainly started better cold with less choke.)

The main jet says 195, which must be Dyno because I don't think the Mikuni jets even go that high? Even so, a 195 Dyno translates to something bigger than a 180 Mikuni. Does that seem a bit high for an otherwise unmodified engine? Does that suggest perhaps a larger needle was used? If so, how do I tell?

Before I changed the pilot it ran well at higher throttle settings, but had a stumble off-idle which was worse in cold weather and especially in cross-winds from the right - which was apparently a ram-air effect. I'm hoping the larger pilot corrects this and I don't need to open up the carb again.

BTW, how many turns on the PMS would you start with? I have it at 2.5, which seems like it might be too rich given how well it started cold...

I'm thinking you're close, but 'wait for it', the Real carb experts will answer you soon...

twowheelsgood wrote:
I have a 2004 R* that I bought used from the original owner with Freedom Racing duals and a BAK. He said he had a shop set up the jetting for the intake/exhaust, but it had a stumble right off idle that suggested a too-small pilot jet.

So I opened up the carb and found a 135 pilot jet, which I swapped out to a 137.5. (Haven't had the chance to try it out yet, but it certainly started better cold with less choke.)

The main jet says 195, which must be Dyno because I don't think the Mikuni jets even go that high? Even so, a 195 Dyno translates to something bigger than a 180 Mikuni. Does that seem a bit high for an otherwise unmodified engine? Does that suggest perhaps a larger needle was used? If so, how do I tell?

Before I changed the pilot it ran well at higher throttle settings, but had a stumble off-idle which was worse in cold weather and especially in cross-winds from the right - which was apparently a ram-air effect. I'm hoping the larger pilot corrects this and I don't need to open up the carb again.

BTW, how many turns on the PMS would you start with? I have it at 2.5, which seems like it might be too rich given how well it started cold...

I'm hoping the 135 and the 137.5 are typo's.


2 1/2 is probably pretty close for the PMS, if you have the correct Pilot. Is it a Mikuni 37.5? If it is a DJ, then it is the same size as the 35 Mikuni that was in the bike when it was stock.
Open exhaust and intake like you have, could use a 40 Mikuni Pilot. It is considerably more free flowing, and does require rejetting. You could get closer to a 172.5 Mikuni(185 DJ) if your using a DJ or Barons needle. The clip should be in the 4th groove from the blunt end(top). You should have a plastic spacer and a silver washer(shim)under the clip, also. Clip position is important. If you're too rich on the needle, for instance the clip in the 5th groove, then the proper Pilot will seem to rich for the bike. The clip position on the needle, determines how rich or lean the transition between the Pilot and Main circuit is.

These Bike start great when they have the proper Pilot, and you follow the proper starting procedure. I don't understand your concern about having to use the Enricher. It *should be necessary. You should have it full out to start, and within about 10 seconds or so, when the rich lumpy idle starts, you can ease it in to about halfway, and leave it there until the bike is warmed up good.....which could be one or ten miles, depeneding on temps and conditions(ie, stop signs, lights, or open road). The bike will run a bit ragged until it is well warmed up.
Don't mess with the throttle during the starting sequence, until you're ready to ride away. When the rich idle gets lumpy, don't touch the throttle, just ease the enricher in a tad. You will actually hear the motor smooth out some, when you ease the enricher in a bit. If you twist the throttle when the enricher is out and the rich idle starts, you will ruin the vacuum that makes the enricher work, and the bike will die.

Make sure the hot idle is set to about 900rpms, then don't mess with it anymore. Especially, when the bike is cold.

Thanks, yes the pilot jet number was a typo. I changed it from 35 to 37.5. Will check needle position next.

Update: got the chance to ride the bike today in all types of conditions from traffic to open country roads to a short blast on the freeway. Response is noticeably better, especially when just opening the throttle. And once warmed up it no longer spits back thru the carb when the throttle is opened slowly, which it used to do especially on cooler days.

I'd say the pilot jet was a success! I just filled the tank to run a fuel economy check. What other tests are suggested to make sure it is jetted as optimally as possible? (Aside from dyno testing, which I'm not going to spend the $ for.)

How many turns out on pms you should be with 37.5 pilot on 1600 rs?



SKWEARpeg wrote:
twowheelsgood wrote:
I have a 2004 R* that I bought used from the original owner with Freedom Racing duals and a BAK. He said he had a shop set up the jetting for the intake/exhaust, but it had a stumble right off idle that suggested a too-small pilot jet.

So I opened up the carb and found a 135 pilot jet, which I swapped out to a 137.5. (Haven't had the chance to try it out yet, but it certainly started better cold with less choke.)

The main jet says 195, which must be Dyno because I don't think the Mikuni jets even go that high? Even so, a 195 Dyno translates to something bigger than a 180 Mikuni. Does that seem a bit high for an otherwise unmodified engine? Does that suggest perhaps a larger needle was used? If so, how do I tell?

Before I changed the pilot it ran well at higher throttle settings, but had a stumble off-idle which was worse in cold weather and especially in cross-winds from the right - which was apparently a ram-air effect. I'm hoping the larger pilot corrects this and I don't need to open up the carb again.

BTW, how many turns on the PMS would you start with? I have it at 2.5, which seems like it might be too rich given how well it started cold...

I'm hoping the 135 and the 137.5 are typo's.


2 1/2 is probably pretty close for the PMS, if you have the correct Pilot. Is it a Mikuni 37.5? If it is a DJ, then it is the same size as the 35 Mikuni that was in the bike when it was stock.
Open exhaust and intake like you have, could use a 40 Mikuni Pilot. It is considerably more free flowing, and does require rejetting. You could get closer to a 172.5 Mikuni(185 DJ) if your using a DJ or Barons needle. The clip should be in the 4th groove from the blunt end(top). You should have a plastic spacer and a silver washer(shim)under the clip, also. Clip position is important. If you're too rich on the needle, for instance the clip in the 5th groove, then the proper Pilot will seem to rich for the bike. The clip position on the needle, determines how rich or lean the transition between the Pilot and Main circuit is.

These Bike start great when they have the proper Pilot, and you follow the proper starting procedure. I don't understand your concern about having to use the Enricher. It *should be necessary. You should have it full out to start, and within about 10 seconds or so, when the rich lumpy idle starts, you can ease it in to about halfway, and leave it there until the bike is warmed up good.....which could be one or ten miles, depeneding on temps and conditions(ie, stop signs, lights, or open road). The bike will run a bit ragged until it is well warmed up.
Don't mess with the throttle during the starting sequence, until you're ready to ride away. When the rich idle gets lumpy, don't touch the throttle, just ease the enricher in a tad. You will actually hear the motor smooth out some, when you ease the enricher in a bit. If you twist the throttle when the enricher is out and the rich idle starts, you will ruin the vacuum that makes the enricher work, and the bike will die.

Make sure the hot idle is set to about 900rpms, then don't mess with it anymore. Especially, when the bike is cold.

2 1/2 should be plenty.