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Old April 24th, 2010, 03:09 PM   #1
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Keihin OEM vs Factory Pro jet sizes

Do the numbers mean the same, or is there a conversion necessary to compare like kind jets?
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Old April 24th, 2010, 03:25 PM   #2
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um, who the hell is Klein??? do you mean Keihin?
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Old April 24th, 2010, 03:58 PM   #3
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Quote:
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um, who the hell is Klein??? do you mean Keihin?
LOL, you know Klein, as in German for "small?"

Yeah, yeah, and as dumb as it may sound, my eye has always skipped over that word and interpreted it as "Klein." I have a friend who actually did his dissertation on this phenominon.... boring, as all dissertations are, but he took the easy way, being that it happened to be an interest of his dissertation advisor... at this point he just wanted to be DONE!

So, I'll try again. Keihin OEM vs Factory Pro jet sizes, do the numbers mean the same, or is there a conversion necessary to compare like kind jets?
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Old April 24th, 2010, 04:01 PM   #4
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Bob,

If you are seriously thinking of rejetting, you need to read up on it a bit more. I'd start with the jetting database thread... among others.

http://www.ninjette.org/forums/showthread.php?t=10208
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Old April 24th, 2010, 04:08 PM   #5
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Quote:
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Bob,

If you are seriously thinking of rejetting, you need to read up on it a bit more. I'd start with the jetting database thread... among others.

http://www.ninjette.org/forums/showthread.php?t=10208
Ahhh, trying to head off more dumb questions and mistakes

Yes.... I have been perusing the rejetting threads since the beginning, although since I wasn't ready to do it until recently, I didn't study them deeply. I have since developed more mechanical confidence, and some more understanding, although still at a basic to basic-moderate level. I definitely plan on continuing to reference this material as I continue to tune. In particular, I have been reading through the article on the FP website in regards to their method of tuning (ie: starting with main jets for WOT, and incrementally working your way down to idle and mixture screws). This is the plan anyways. Am I on the right track?
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Old April 24th, 2010, 04:15 PM   #6
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The reason for the "warning" is that screwing up the jetting can have disastrous results if not approached with a firm understanding of the potential downsides.

For general jetting advice, I like to use this...
http://faq.ninja250.org/wiki/I_want_...uretor_jetting
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Old April 24th, 2010, 04:33 PM   #7
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I was just reading this

Great minds.
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Old April 24th, 2010, 04:45 PM   #8
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All the jet sizes from different manufacturers are different . And it is not just the hole size but the length of the jet that changes the flow rate. I only use Keihin jets for the sake of consistency. One is no better than the other, My feeling is If you are using Dyno jet needle then use a DJ jet. I am not fond of mix and match. BUT what ever works works .
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Old April 24th, 2010, 04:49 PM   #9
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I'm currently using 3 washers under my stock needles (stock everything). Based on the reading, my understanding is that I need to remove the washers to put it into stock config. prior to starting to tease out the proper main jet... is this correct?
(but leaving snorkle out is OK because it is outside the carb???)
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Old April 24th, 2010, 06:03 PM   #10
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nah, you can leave the washers in to test for the proper main. at WOT, the needles should be raised sufficiently in the needle jet so that the tapered portion of the needles are no longer in play.
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Old April 26th, 2010, 04:38 PM   #11
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I expect delivery in 30-60 min.

I have also been heeding the Kelly's "warning" buy going back through the jetting discussions here, read all the wiki articles over at faq.ninja250.org, and have been reading, and re-reading the Factory Pro procedures at http://www.factorypro.com/tech_tunin...m_engines.html

The past two days I have been doing WOT tests to see where I am at with the main jet. I know a lot of people w/o stock pipes don't need to change it. Based on my tests, the difference between cold and warm isn't supper obvious to me, but the weather is warming up and the bike is at operating temp. within 5 minutes - easy. I suspect it is a little better warmer, based on overall performance, but like I said, it isn't obvious enough to be sure at WOT. The power at WOT doesn't start until ~8K or 9K RPM, then it scoots along a little better. I don't have anything to compare the power to, so I don't know if it is the "best" jet, but my arse dyno did expect A TOUCH more kick. Is it worth it to try one main jet bigger just to be sure stock is where I should be at (if so, what is the corresponding FP number)? Or does it sound like my expectations might night be realistic and this is all I should expect to get, or is it not worth pulling the whole thing out based on other's experiences? I want to do it right, so if I need to get my hands dirty, I am willing, although not looking forward to the hassle.

Unfortunately I don't find a whole lot of people in the jetting db with stock pipes
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Old April 26th, 2010, 04:42 PM   #12
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Bob, I bet you would get more "GO" with an "old" pre-gen CDI or a BRT-TIS, along with your original OEM 98 jets and FP needles! Without changing the exhaust!
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Old April 26th, 2010, 05:03 PM   #13
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Bob, I bet you would get more "GO" with an "old" pre-gen CDI or a BRT-TIS, along with your original OEM 98 jets and FP needles! Without changing the exhaust!
Yeah, I have no plans to change the exhaust.... I like to run a little quieter, cheaper, and don't want to run into the CA emissions Nazis.

Does the pre-gen CDI have advanced timing (I know the BRT does)?
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Old April 26th, 2010, 05:15 PM   #14
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Does the pre-gen CDI have advanced timing (I know the BRT does)?
Yes, almost the same. Check out the DIY and look at the timing graphs. You need to get the non-CA pregen version, which is what kkim and I have.
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Old April 30th, 2010, 11:17 AM   #15
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Sorry to drag this out, but I didn't get an answer to my question about the main jets.
Revised Q here: The past two days I have been doing WOT tests to see where I am at with the main jet. I know a lot of people w/o stock pipes don't need to change it. Based on my tests, the difference between cold and warm isn't supper obvious to me, but the weather is warming up and the bike is at operating temp. within 5 minutes - easy. I suspect it is a little better warmer, based on overall performance, but like I said, it doesn't seem to be pulling any harder or less at WOT between hot and cold. The power at WOT doesn't start until ~8K or 9K RPM, then it scoots along a little better. I don't have anything to compare the power to, so I don't know if it is the "best" jet, but my arse dyno did expect A TOUCH more kick. Is it worth it to try one main jet bigger (or smaller) just to be sure stock is where I should be at? Or does it sound like my expectations might be unrealistic and this is all I should expect to get, or based on other's experiences, is it not worth pulling the whole thing out for? I want to do it right, so if I need to get my hands dirty, I am willing, although not looking forward to the hassle.

Thanks!

Last futzed with by headshrink; April 30th, 2010 at 12:41 PM.
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Old April 30th, 2010, 12:58 PM   #16
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you still have the snorkel in? if so, you're running a bit rich.

another warning... you should not run the bike WOT until it's fully warmed up.

Last futzed with by kkim; April 30th, 2010 at 07:14 PM.
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Old April 30th, 2010, 02:54 PM   #17
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Quote:
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you still have the snorkel in? if so, you're running a bit rich.

another warning... you should run the bike WOT until it's fully warmed up.
There should be a "not" in there -- don't run WOT until you're warmed up.
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Old April 30th, 2010, 03:19 PM   #18
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Thanks Kelly and Trey, that helps clarify my question. For the record, normally I would NOT ride hard when cold at all, but I was following the FP instructions to the letter (which didn't seem to conflict with other stuff I read here or the other forums). Since it talks about comparing warm and cold up high at WOT, I figured this was one of those exceptions just for diagnostic purposes....
Marc from FP and I have been trading emails today, and I was confused by the hint he just sent about trying a step lower. I only told him what my setup was, not the road tests, and thought stock exhaust people stayed at #98 and a small number have gone to #100.... I just can't recall reading about someone who went lower, must have missed it. So, all that to say that it is becoming more clear.... thanks for the clarification and hint!
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Old April 30th, 2010, 05:22 PM   #19
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BTW: This is in regards to the official word about my jet number question. http://www.ninjette.org/forums/showthread.php?t=43584
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Old April 30th, 2010, 05:44 PM   #20
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Er, Bob, I might have spoken too soon -- I just assumed (ass out of me, etc.) that Kelly was referring to the fact that it's generally a bad idea to wring the little engine's neck until it's warmed up. I didn't know that running the engine cold at WOT (maybe?) is part of the jetting procedure.

I have no expertise in this, so I'm going to back out of this conversation and let somebody else clarify. Sorry!
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Old April 30th, 2010, 07:14 PM   #21
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Quote:
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There should be a "not" in there -- don't run WOT until you're warmed up.
thanks! sorry for that. corrected in my original post.

you were right... it was a missing word on my part.
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Old April 30th, 2010, 07:17 PM   #22
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Bob, this is why jetting should be done after all the hardware has been installed. You are trying to put the cart before the horse... don't do that.
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Old April 30th, 2010, 11:12 PM   #23
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Bob, this is why jetting should be done after all the hardware has been installed. You are trying to put the cart before the horse... don't do that.
I feel like we are soooo close, yet just barely, barely not quite, although partially, on the same page..... what equipment are you referring to? I don't have any equipment, and am not planing to add any equiptment...... except MAYBE doing one of those timing advance thingies down the road.....


I have this pit in the bottom of my stomach, like I am about to have a bubble burst that I didn't even know was there.
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Old April 30th, 2010, 11:33 PM   #24
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As I stated in another post you made, I got PMs mixed up in my brain. Refresh my memory... what exactly do you plan to do with your intake and exhaust while you jet?
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Old May 1st, 2010, 12:19 PM   #25
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As I stated in another post you made, I got PMs mixed up in my brain. Refresh my memory... what exactly do you plan to do with your intake and exhaust while you jet?
No problem. I plan to keep my stock pipe, and although I considered addinging a K&N drop-in for my stock airbox, didn't think it would do much, based on what I was reading at the faq forum, so I will likely just keep my stock air filter as well. I did remove my snorkle a while back however. Basically I wanted to rejet to get the smoothest/most power delivery that I could eek out without more expensive and loud mods.

I did talk about getting the brt tis on another thread, but that is on the back burner for now.... if it helps, I may do it in the future, but for now... rejetting was all I was doing.
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Old May 1st, 2010, 01:33 PM   #26
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so, stock airbox w/ snorkel removed and possibly a free flowing air filter, but stock for now. stock exhaust.

98 mains should work well with that setup, possibly a 96, but I would start with the stock 98s and work from there unless they seem to be flat on top, which I doubt.
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Old May 1st, 2010, 02:18 PM   #27
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so, stock airbox w/ snorkel removed and possibly a free flowing air filter, but stock for now. stock exhaust.

98 mains should work well with that setup, possibly a 96, but I would start with the stock 98s and work from there unless they seem to be flat on top, which I doubt.
Yes, that's right about the setup.

Marc from FP suggested starting with a #92 and "maybe" #95 with my current setup. That does sound WAYYY to lean to me, and I haven't heard of anyone going that lean, but then I haven't done this before. #95 is the next step down that I have available to me from the jet kit, so I would have to try that over the #96.

I'm pulling the carbs right now to give that a try (PITA). My instinct does say stay at #98, but this will at least give more data to work with.
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Old May 2nd, 2010, 03:12 PM   #28
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Here is the latest on attempt #1. Once I am satisfied it is all dialed in, I'll add it to the jetting db.

Main Jet = #95
Needle = 3rd clip
Mixture screws = 2.5 turns out (ea.)

This is based on all the advise I have gotten, and threads I have read.
Removing and reinstalling the carb was so distasteful, I do NOT wish to do that again. It literally took all day just to do that. If I have to change jets again, I'm going to try it on the bike, as Vex did in his DIY. When I drilled the caps, I actually broke part of the metal wall off (screw went in too far and expanded the space a bit).... fortunately it was only the outer lip, and not close enough to the mixture screw to effect it in any way.

Once I got the carbs synced, I went for a test ride.....
Idle holds smooth.
When I blip the throttle, it MIGHT be falling slightly slow, but it isn't hanging at all.
There is a remarkable improvement in the low end and midrange. When I originally shimmed my OEM needles, things improved, but this was at least twice as good (happy about that).
Overall power-delivery feels relatively smooth and fairly linear, but it feels as if it should pull a LITTLE harder at the top end. I can't quite tell for sure if it is any better or worse than when I started though, it is pretty subtle. However, I suspect it MAY not have the top end boost at 9K+ RPM. Based on the better-than-expected performance change at low and mid RPM, I really do expect more up top. I'll be watching this over the next couple days.
Also, I need to watch for minor surging down low, and popping on decel.... I MAY have heard a couple very small pops, but I need more time in the saddle to be sure. I think the potential surging may have only been when warming up, but again, it may have been my imagineation.... will be watching for it.

How am I doing so far?
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Old May 5th, 2010, 02:54 PM   #29
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Update: I'm still not sure about the main being perfect yet.
Mid and low seem sig. improved.
I have not heard what I thought was popping on decel.
BUT.... today on my way to work, I noticed a very subtle surge (maybe a stutter... that would be the opposite), at ~ 5-7K RPM and 1/8-1/4 throttle.
I did a search, and from what I understand, this means the idle circuit is lean? If I were actually feeling a stutter, would that be different (lets hope it isn't a CDI issue throwing me off)?
As far as a solution, shall I try turning out the mixture screws 1/4 - 1/2 turn (currently at 2 1/2), OR should I put in the FP pilot jets that were included with the kit?

EDIT: I should add, I wasn't driving as "spirited" as normal. I believe if I had, I wouldn't have noticed the possible surge. In fact, at first I thought it was the road.... but it wasn't.
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Old May 5th, 2010, 05:23 PM   #30
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I had the same stutter at cruising speeds with light throttle applications. Richening up the idle circuit helped to get rid of it. Installing the FP richer pilots would work, too. your call.

http://www.ninjette.org/forums/showp...39&postcount=3
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Old May 5th, 2010, 09:04 PM   #31
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Wilco, and report. Thanks.
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Old May 9th, 2010, 02:06 PM   #32
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Update: I'm getting more confused and frustrated. I turned out 1/4 turn (2 3/4 total), and didn't notice much of a discernible difference with the surging (always syncing between tests, and double confirming I am turning the screws in the proper direction). So I then turned it out 1/4 turn more (3 total), and it seems to be a little worse. I believe there may also now be a flat spot at 6.5K-7.5K with light throttle.

Could I be confusing surging with bogging? It still seems relatively lively and isn't lethargic feeling.
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Old May 9th, 2010, 02:18 PM   #33
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try moving the needles down to the 4th clip position. this will affect the mixture screw settings and you'll need to redo them.
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Old May 9th, 2010, 02:26 PM   #34
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try moving the needles down to the 4th clip position. this will affect the mixture screw settings and you'll need to redo them.
I'll try that. I don't recall many people going to the 4th clip (especially stock), but it sure is worth a shot. Shall I start with screws reset at 2.5 out as a base, and work from there?
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Old May 9th, 2010, 02:30 PM   #35
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Shall I start with screws reset at 2.5 out as a base, and work from there?
yep... or you can leave them where they are and work from there.
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Old May 9th, 2010, 03:46 PM   #36
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This is a nice read:

http://www.motorcyclecruiser.com/tec...ion/index.html
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Old May 9th, 2010, 09:30 PM   #37
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Cool, it is gelling more and more. I found it interesting though that they suggest the exact opposite of what we do (bottom up, instead of top down).

I really like that tape method. I'm going to do that tonight so I can be more confident about the data I am collecting.
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Old May 14th, 2010, 11:24 AM   #38
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Update: I just return from a test run of tunning attempt #5, after raising the needles to the 4th clip position. Actually I kept the clip at 3rd and added 2 of the supplied washers to equal the equivalent of the 4th position.... did this because those clips are TIGHT and I didn't want to damage anything pulling them on and off. I also haven't toughed the mixture screws since last tune (still at 3 turns out).

Verdict = the bike continues to idle smoothly, pull smoothly.... I don't know if it is the temp and barometric pressure today, but it might even be pulling better than before, not sure. The problem is I am still getting that surging feeling from 1/8-1/4 throttle (I used tape so I KNOW this was the actual throttle position). The surging was showing up ~5.5K to 7.5K RPM. I'm not positive, but the surging actually SEEMS more pronounced at the higher end of that range than it did before, but the flat spot seems gone. If I hadn't been pulling better, I would thing I was confusing surging for bogging.

I'm going to go turn the screws out one more time to 3.5 turns out, and test.

How am I doing, any thoughts?
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Old May 14th, 2010, 11:44 AM   #39
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sounds like it might still be a bit too lean.

you can richen up the mixture screws a half a turn to see if that helps the stutter.

as an experiment, try reinstalling the stock filter and see if that changes anything.

as a last resort, I'd try 98 mains to see if that will richen it enough to get rid of the stutter. Keep in mind that all the work to jet the needles and mixture screw settings will change and will need to be redone.

Also, change only one thing at a time and test between each change to note the difference each one makes to the power delivery.
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Old May 14th, 2010, 12:05 PM   #40
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sounds like it might still be a bit too lean.

you can richen up the mixture screws a half a turn to see if that helps the stutter.

as an experiment, try reinstalling the stock filter and see if that changes anything.

as a last resort, I'd try 98 mains to see if that will richen it enough to get rid of the stutter. Keep in mind that all the work to jet the needles and mixture screw settings will change and will need to be redone.

Also, change only one thing at a time and test between each change to note the difference each one makes to the power delivery.
I do have the stock filter, no snorkel though.
Since I'm working on the pilot circuit (proper term or is it idle circuit?), you think I should try the FP pilot jets supplied with the kit prior to moving to a 98 main?
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