ideas for my jetting

[subxero]

Hey all,

Yesterday i removed airbox, kleen air sys, then installed POD filter, emissions block off plate, nojima moto gp full exhaust, I shimmed needles and changed pilot and main jets.

So here is where i am at

3 washers under needle
Initially installed 115 Kelhin mains
#40 pilot
Did not touch floats,
Did not touch idle mixture screws...yet

With this set up i did a quick ride testing throttle at various positions ect...

At idle after a blip the rev needle returns to idle speed with no hang or drop. Seems good
1/4-3/4 throttle all seems smooth and responsive.
WOT i felt flat and lazy from 6k-11k with no hesitation but then came on strong after 11k to limit.

Then i would get a good bit of backfire when decel with no throttle after 3/4-WOT

Wasn't sure which way to go but seems like my main jet is primary issue
I had 118's and richer is safer so i put the 118's in today. Did a quick test ride. idle -3/4 throttle felt good still, maybe better,
WOT felt better 6k-9k but 9k-11.5k ish i get hesitation type symptom,
then 11.5k-limit it pulls really strong.

Still lots of backfire when decel no throttle. IF i put choke on full and decel there is no backfire.

The backfire on decel would seem to be a lean condition because the choke or throttle cures it right? All the circuits less the MAIN seem to be good on the way up the revs so why would one not be good on the way back down?

Is it more possible my MAIN is RICH, or LEAN and the backfire is a by product of the MAIN jet being off? and has nothing to do with other aspects of the carb tuning?

Out of tune main jet leaves excess unburnt full? or is to lean to ignite mixture and then it is ignited by next cycle further down the pipe?

I have 120 mains laying around somewhere, i need to find them. I have 1 112 main and would need to order one more before i could try them.

I also have BRT-TIS, i feel like i could probably play with the ignition timing a little and it might help with the hesitation i am getting with the 118 at 9k-11k

Thoughts?

[DaBlue1]

For your elevation your, mains and pilot jet are too big. 38 pilot and 112 mains jets should work.
Motorcycle Carburetor Theory 101
http://www.motorcyclecarbs.com/carbs101.pdf

A Typical Rich Condition is when

-The engine acceleration is flat and uneven and loses that "crisp" feel.

Here is a Dyno Chart of the maps for the non programmable BRT i-DTIS. Should help give you an idea of where the changes should be. Map 2 is for higher octane.

[subxero]

Originally Posted by DaBlue1

For your elevation your, mains and pilot jet are too big. 38 pilot and 112 mains jets should work.
Motorcycle Carburetor Theory 101
http://www.motorcyclecarbs.com/carbs101.pdf

A Typical Rich Condition is when

-The engine acceleration is flat and uneven and loses that "crisp" feel.

Here is a Dyno Chart of the maps for the non programmable BRT i-DTIS. Should help give you an idea of where the changes should be. Map 2 is for higher octane.

Yeah, thinking i was to rich to begin with but didn't have the 112s and again trying richer first is safer. WIll order another 112 to try out. See what happens, if still backfire will try putting stock pilots back in.

I need to double check all my vac lines ect... to make sure they are all connected good with no leaks.

[subxero]

My 112 main's should get delivered today so with any luck i will instal them after work and see how she runs and go from there.

[subxero]

So USPS never delivered my jets, in tracking says undeliverable as addressed Called them and there is no way i can get it, and their policy is to immediately return to send. Seriously? I called 1hr after failure to delivery was posted one would think i would be able to just pick it up at the USPS center or something.

Either way i reordered maybe they will deliver them this time. Jetting work postponed till most likely next week, don't expect to get new jets till Monday.

[mgentz]

I am starting with 42 pilots and 112 mains and my bike is heavily modded. I think most people run themselves much too rich. Others may disagree but actually running leaner creates more power up top. The trick is not to run too lean and kill the motor.

popping on decel indicates a lean pilot circut. You should be fine with the 40 pilots but you NEED to adjust your mixture screws to 2 - 2.5 turns each. There are tutorials on here and other sites about how to hone in the screw settings.

as for the mains, I would try 105's or so. From there, if you cannot get dyno time, use the method described by Factory pro on their site to hone the jets in.

[subxero]

Finally got my jets in today. Was getting late, slapped in the 112's and took it for a quick cruise and the bike felt much better at WOT and i had no backfire/popping on decel.

But i did remove and reinstal my exhaust trying to fix a potential leak so it is impossible to say if it was the jetting causing the popping or if i had a leak that was fix.

Either way i am just glad that it seems to be running good again.

[subxero]

Road to work today and the bike felt decent but i think there is room for improvement. Probably try messing with a few of the washer shims to see how it affects the mid range and maybe pop the 110 mains in and see how they feel as well.

The pilot should not affect the mid range correct?

edit: Think i'm just having a convo with myself now so did not seem reasonable to add a new post so i will just add by edit

Took bike to work again today and definitely feel like my main jet is still to rich in the mid RPM range the whole way up to 11k after 11k it starts to come to life, With the airbox delete these bikes must run lean past 11k because the 118's i had in originally pulled pretty hard past 11k to redline so the lower and lower i go to bring the 7-11k back to life the leaner the 11-14k range gets but i would rather have more power 7-11k
I will definitely try the 110's and probably the stock 38. i really would like to change them one at a time so i could feel the difference for each change individually but i don't feel like tearing the carb apart twice. The main jet is mainly WOT so i should be able to still tell what each change did. 1/4 throttle doesn't feel bad, pretty good, but 1/4-3/4 feels off still, thinking rich but what is the best way to tune A/F in the mid throttle?


another installment

today was playing with choke at various throttle positions and i think my 1/2 throttle is lean. seemed to run better with choke on

rejetting this weekend, figure i will throw the 110's in, thinking this will lean out the 1/2 throttle position even more so figure i will also add another washer or two under the needle to raise them up to hopefully help with that. Not sure what else to do to richen 1/2 throttle other than buying a completely different needle.
There are the actual needle jets that sit above the Main jet in that circuit. Has anyone ever messed with these? Stock is listed at a #6 but i have never seen alternatives for sale which probably means (don't mess with it) IDK

edit 5/18/13
So i am planning on doing some carb work today and been trying to plan out what i intend to do. So simply crack open the bowl put in the 110's reassemble. Then i will open the top and address the needles. I already have 3 #4 washers on each needle. But i am quite positive my mid throttle is lean. Figure since it is lean now and i will only make it more lean by putting in smaller main i will shim with another 2 washers? 5 total, is this ok? I will measure the complete height of the 5 washer shim to see if it seems reasonable. The factory pro needle with clip allows for 4mm of adjustment from min to max. I figure as long as i am in this range things should be fine. I have not mic'd any of the washers to see individual thickness as my calipers are on vacation somewhere so again i will just measure the total thickness of 3 or 5 washers together for a rough idea.
I was hunting for other needles that would work for the 250r but could not find any for sale just as needles. I don't want to waste money on a jet kit just for the needles, But i might end up buying a kit if the 110 mains are still to rich at WOT as they are the smallest mains i have. So if i can find a kit that has the equivalent of the kelhin 108's and lower in it with the needles i will probably pull the trigger. I was looking at the minkuni needles and found some that would work but the tip diameter seemed to large and therefore would not solve my to lean problem most likely make it worse.
So yeah, 110 mains, potentially 5 #4 washers under the needle, then i need to adjust idle mixture screws and hope i can keep them at a reasonable distance in and or out. If not might have to go back down to the #38 pilot jet to help lean out idle and 1/8 throttle.

update soon to come.....this might be turning more into a blog

5/19/13 edit

Re shimmed the needles today. Went out to look for some more washers, went to a hobby shop and found some #4 and some 3mm washers, bought all they had.....1 bag of each, 8 washers/bag

Fought with stock JIS screws on top of the carb got everything apart. the #4 washers i bought from Lowes were at little bigger both dia. and thickness than the ones i bought form hobby shop. 3 lowes #4 ~ .09" 3 hobby shop ~ .08". the #4 and 3mm from hobby whop were very similar in both dia and thickness. So original idea was to go from 3 washers to 5 of the lowes #4's would be around .14" 5 of the hobby shop washers around .12" I decided to use 5 of the hobby shop washers as it was not quite as drastic as a change and i liked the smaller Dia. Had to take a break... i was baking a ham
Took care of the ham, then decided to go look for some M4 screws to replace JIS screws in top of carb. Lowes blows for metric...enough said. Went to hobby shop and found some M4 hex, they had 1 bag of M4 x 18mm which seemed slightly to long, and 2 bags of M4 x 14 which seemed to short.

Got back to place, used the x14 for the holes that did not have the other mounting stuff on them. they seemed like they grabbed enough thread. Used 3 of the x 18mm on the 3 spots that hold the hose and cable bracket. I only had 4 of those and they were to long for a few of the holes as they would hit something else.

Put gas tank back on, seat and started it up. Started up fine with full choke, let it warm up a bit to choke slightly off and putted around parking lot for 3 minutes just to feel if the idle and 1/8th throttle felt super boggy but it did not. Did not have time to do proper test and need to do mains so i did not have fairings on. Shut it down and covered it up for tomorrow. will put mains in and do a proper road test. Most likely adjust idle screws.

[subxero]

So I put the 110 main jets in today. Threw everything back together and went for a test ride.

The bike feels much, much, MUCH better. And a lot of the previous observations i made make sense. Like when i went from the 115 to the 118 i thought the mid range and mid throttle felt a little better. Which makes sense because it was lean.

So yes, 5 washers, ~ .12" raised from stock height and the mid throttle and mid range feels much improved. With the 110's the WOT is significantly improved and pulls nicely.

Not sure if i should try the 108's or not. I don't have any so would have to order them specifically.

I still need to mess with idle mixture screws and sync the carbs

but all in all the bike is running good again and is fun to ride.

5/20/13 edit/update

So road to work today and the bike still feels good. Definitely rich at 1/8th throttle so i might go back to the #38 pilot and hope that it does not affect my 1/4-1/2 throttle to much as i think it is pretty spot on. As far as the main jet is concerned i am thinking i might be a hair rich at WOT between 9k and 11k rpms. The bike pulls pretty good especially at 10.5-12k but i thought i noticed a slight hesitation today when i cracked the throttle a few times. However i feel like i am starting to split some hairs here as i definitely think the bike runs very lean from 12k-14k not that i run that range very often but leaning out the main jets any more and i am thinking i might have to be careful with sustained throttle in the 12.5-13.5k range so top speed runs might be a bit risky. But i could potentially get more usable power in the 9-12.5k range with the 108 main jet which i think would be great.

I kind of wish there was another circuit to tune for these bikes to get more power out of the high revs. I guess the bike isn't made to be run past redline in all but I know when i had the 118 main jets in the engine would come back to life after 11.5k rpms and pull hard past redline. I can definitely see why using a larger main jet for a top speed build could be beneficial.

I need to order some kehlin 108's, I might buy some random minkuni needles that look like they will fit for fun as well. i might get around to putting the jets in not this coming weekend but the next. And then after i try the 108's like or dislike maybe end up going back to the 110's. i need to get the carbs synced and then get this thing to a dyno see where things are at, adjust if i have to and maybe do some fine tuning of with the ignition timing.

So far so good though.

[subxero]

So my curiosity got the best of me and i wanted to see what the factory pro needles had to offer so i ordered the stage 3 kit.

For $75 you get 2 110 mains, 2 112's, 2 115's, 2 #40 pilots, a handful of shims and clips, 8 hex screws for the top of the carb, and of course the 2 needles. The jets are Keihin.

So to order all the jets from lets say jets r us you are looking at around $45 bucks, if you can find the right size hex screws somewhere they might run you $4... if you can find them. shims and clips maybe $1 So around $50 value of jets and screws not including the needles which in reality is what you are buying. Is it worth it... sure if you are starting from scratch. The hex screws are nice and not having to hunt for them is great. Getting a variety of jets is nice... unless you know exactly what your main jet is going to be from the start or you have some already, in my case i don't need the jets i already have all these sizes i just wanted the needles to play around with.

Ok cut to it,


I posted a pick of the FP needle next to the Stock needle in the new gen jetting data base. The FP is longer, and the taper does not start till ~6mm after the stock needle taper. The FP taper is much sharper and short as well. Theoretically this should richen up the mid range throttle response while keeping the 1/8th throttle where it needs to be if i am thinking correctly. Using my shimmed stock needles as starting point i put the clip on the 4th position of the FP needles and put them in.

Road the bike today, It definitely leaned out my 1/8-1/4 throttle which is great as it was running rich with the stock needles with 5 shims #40 pilot. It has also made my mid throttle mid range slightly rich which makes sense with the new needle taper over the stock taper and the heights at which i set the FP needle to. I will move the clip probably to the 3rd position and see how the bike runs, should slightly lean out my mid throttle.

In the end does it seem like the FP needles were worth it.... hard to say, again if you are starting from scratch sure, you should get what you need to jet the bike, but i don't think the FP needles have much to offer over the stock needles. My bike was running good with the stock needles and the 5 shims, if i would have gone back down to stock pilot i think the jetting would have been near perfect. After i get the needle height correct with the FP needles i will have a better idea and if they are any better.

So no kit it would cost you around $50 to jet and get it good
With the kit $70-$80 but you get new needles and screws that you know work with the carb

you be the judge


Edit 6/6/13

Bike ran decent on way to work. It poured rain on the way home so it was a little cooler as well and the bike ran much worse in the rain. I might be a little lean actually in the mid throttle. I will have to ride it a little more to get a better feel for what it is doing.

Edit 6/8/13

Lowered needle and put clip on 3rd position. Leaned out my mid throttle a little bit, feels better but think there is still room for improvement. Either going to go another 1/2 step or 1 full step. Prob go to 2nd clip position and see how it runs.
With the rain the other day, i am thinking the pod filter must of gotten a little moist or damp and caused changes in air flow to make the bike run poor, IDK

Edit 6/8/13 #2

Went back out and adjusted needles, went to #2 position. As the bike was warming up it felt lean in the 1/8th - 1/2 throttle range. After it warmed up completely it was still slightly lean in that throttle range....BUT, 1/2 - WOT pulled the best it has out of all my setups. So this tells me the big needle taper is spot on and the height of the taper is spot on and the Main jet is really good as well. The problem now is with my needle sits to deep and the first taper (nearest to the clips) is to low and or not big enough. i need to figure out how i am going to correct for that. ill play with idle screws first, if i cant get anywhere with that ill think about adding a shim for a half step on the needle which will also effect my 1/2-3/4 throttle but hopefully not to much as i think it is spot on. i think a 42 pilot would be to big but dunno, changing the pilot is probably the last thing i will try.

Other option is to try the 108 main which i am kind of curious about, thinking it would run well but not sure if i want to risk the engine. Being a little rich at WOT isn't a terrible thing and gives you a little safety buffer. But switching to the 108 would lean out my mid throttle allowing me to go back to the 3rd clip position on the needle potentially solving all the problems as long as WOT wasn't to lean.

Wish i had like 2 free days where i could do nothing but work on my jetting. I could get this wrapped up so quick. Only being able to work on the bike during weekends and adjusting things and not getting to test till next day or having to put bike completely back together to ride to work during the week is making this take quite a long time. Plus i guess i keep trying new things which take time to order in. Will probably order 108's and 42 pilots while i'm at it just to have then if i get curious again

the quest for perfect jetting continues

edit 6/9/13

shimmed the needle with clip in #2 position with one of factory pro shims. It raised the needle ~ 0.025" made big difference. bike runs stellar, thinking it will b tad lean come winter but is perfect for summer.

im done until i dyno it

[maverick9611]

intersting info. i'm in the middle of tuning after pod install. went by factory pro instructions on tuning each circuit. have tried 110,112's, and 115's and cleanly can't make to redline. needles are set 3 from top as per factory pro. pilots are 40's. checking valves(reshimmed some out of spec exhaust)adjusted floats to 15mm. also running el cheapo full system from ali express and stick coils. plugs gapped to.030 due to increase voltage of stick coils. maybe my gap is to large? ghostt runs his stick coil plug gap at .032
switched back to 110's and will try again

[NinjaBraap]

One thing about the 08-12 250 especially is they don't like pod filters, and tend to be really hard to get down by feel alone. Unless you're dynoing and have a fuel/air wideband sensor to really hone it, you're just going to be chasing the carbs around forever. Not saying it isn't possible, but in my experience thats why it's taking so much just to find that perfect tune.

Anyway, sounds like you're on your way pretty well and know where you're going. It was fun just to read through this adventure, having gone down that rabbit hole on mine as well. I'm going back to the OEM airbox myself.

[maverick9611]

Originally Posted by NinjaBraap

One thing about the 08-12 250 especially is they don't like pod filters, and tend to be really hard to get down by feel alone. Unless you're dynoing and have a fuel/air wideband sensor to really hone it, you're just going to be chasing the carbs around forever. Not saying it isn't possible, but in my experience thats why it's taking so much just to find that perfect tune.

Anyway, sounds like you're on your way pretty well and know where you're going. It was fun just to read through this adventure, having gone down that rabbit hole on mine as well. I'm going back to the OEM airbox myself.

i’m gonna keep trying, a wideband setup is only $145.

[NinjaBraap]

Sweet! I keep going back and forth on getting one, I'd love to know how that goes.

[maverick9611]

I’ll do a write up when I get it maybe for Christmas

[clakmurrick]

Originally Posted by maverick9611

I’ll do a write up when I get it maybe for Christmas

Sorry for resurrecting this old thread. Did you happen to get a wideband? I'm sure you could attach it to the bike while riding around? If you got it, is that what you did? Thanks!