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I've got a 22 150sx, followed fgr's suggestion of the 42-75 needle and went for a leaner main and pilot as was recommended for pump fuel, current specs are:
520 Main
35 Pilot
42-75 needle, 3rd clip
s4 needle
#5 slide
AS 1.75
Running 40:1 on 91 pump fuel
Bike felt pretty good when riding Tuesday, I would say the bottom end felt noticeably better then before, but when opening up the bike out of a corner and getting into the midrange the bike would stutter a bit. Not sure exactly how to describe it as it wasn't a bog, but a bit of a pause before clearing up and running fine on the top end, temp was around 80 deg F. Any suggestions on how to clear out that stutter would be great, thanks to everyone for all the great information here.
Go leaner on the needle clip. Try 43-75 on clip 2. If you don't have the 43 needle handy, try 42-75 on clip 2 just to tell if leaner is better, but you don't want to go too lean. 43-75 is a 1/2 clip richer needle, so you can split the difference with it and not do one whole clip jump. You may also be better off with a 32.5 pilot, especially if it is muggy with the heat.
@digger @AJ565 @FGR01
Dear all,
I have the following setup as you mentioned, but I'm experiencing the same issue, although it's not as noticeable. At low throttle (barely pulling it), as soon as the slide moves, the bike leans out. In neutral, the rpms slowly increase to the moon :D. When driving it cold, it bogs with the same barely pulled throttle. It's under 1/8 throttle. The bike runs well on idle and at higher throttle positions. What solution do you recommend?
/100 m elevation, now at 30 °C (86 °F), but it's the same in cold 5 °C weather. Fuel is like the 93 premium in USA with 1:40 Motul 800/
Pilot--35
Needle--42-75 in #3 clip position
Main--500
Needle Jet--S-4
Slide---5.5,
air Screw---between 1 and 1.5
Thank you for your answer in advance!
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This is a recent change? It was running good on these settings before?
I would think jet block gasket, or air leak. Possibly the seal on the carb cap sucking air? Might be a small circuit in the jet block clogged with dirt. Have you verified the float height? May be set too lean.
1. I bought the bike last year with OEM carb internals.
2. It fouls the plug, so I changed the block gasket in the carb to the JD type.
3. I bought the carb internals as you and digger mentioned, but it was really lean in low throttle, needed to close the AS.
Pilot--32.5
Needle--42-75 in #2 clip position
Main--500
Needle Jet--S-4
Slide---5.5,
air Screw---1.5
4. Updated the carb internals as digger update (actual setup), and it's way better, but still bogs when cold and feels lean when hot under really low throttle above idle throttle position. Just turn the throttle like 1 or 2mm, the slide moves a bit, and it leans out. Idle is spot on, higher throttle is good:
Pilot--35
Needle--42-75 in #3 clip position
Main--500
Needle Jet--S-4
Slide---5.5,
air Screw---between 1 and 1.5
It's a recent change to the bike; the issue is constant after the new jets, not changing.
First thing I would do is verify the float height.
The float height was 6.5mm when it fouls the plug originally but I increased it to 8mm.
OK, 8mm should be about perfect. Maybe double check it to be sure.
I will check it, any further tips? Is it possible that I need a bigger pilot jet? Or a sharper jet needle?
I did use 37.5 pilot sometimes when my bike was a 250. Easy to try.
Hello brother
Ive been using the jetting setup for the 150sx succesfully. 53°F sea level
5 slide, 37.5 PJ, 500 main , 42-74 3 clip , 40:1 motul 800, 93 oct pump gas . The problem is im a beginner and im not riding WOT, only in the straight part of the track .
i go down to 35 PJ and 2 clip and the bike runs clean and beautiful . The problem is after 4 hours of riding when i turn it off, then i couldnt start up again . I change the spark plug and starts in the first kick and keep running excellent. I think the problem is my riding and not the jetting , im lugging in 3rd sometimes . Im thinking of changing the premix oil to the Motul 710 that has a lower flash point than the motul 800 .Do you think is a good choice or i should try to run a little more on the pipe . Bike runs beautiful, it doesnt sputter or hesitate , just after a few hours, the spark plug is fouled a bit.
Another solution i was thinking is before turn it off , i do in a straight line a few WOT passes to burn the oil .
Yes, all good thoughts. I've always found Motul 800 to be very clean burning despite the very high flash point. But, yes, give 710 a try. Also, giving it a good blowout before shutting it off is a good idea too. What plug are you running? I run the BR9ECMIX. I think the skinny Iridium tip is supposed to be more foul resistant.
BR9EIX and the last one that fouled is BR8EIX and is new . Thought the hotter plug maybe will help . I think i will try the 710 oil because i like how the bike is running , dont think is the jetting
2022 KTM 250sx with the first setting mentioned.
Is the air screw 1.5-2.0 out from all the way in? And why would fuel leak from the vent hose on the bottom of the bowl?
Also, I have the 32.5 pilot in and did some trail riding this weekend. Maybe sounded a touch lean on the bottom it would ping up a bit, would going to a 35 pilot be a great starting point to adjust?
Thanks!
sea level , 53°F
5 Slide without notch
500 MAIN , 35 PJ, AS 1.5 , needle 43-74 2 clip , PV 2 turns, , float height: 7-8mm , 40:1 motul 710
Im having a hesitation when im reaching 1/4 throttle, its more noticeable when im gentle with the throttle in 1st and 2nd gear. If im more agressive with the throttle , the hesitation goes away specially in 3rd, 4th gear. Today i put the 42-74 needle 2 clip, but i cannot test it until thursday. i didnt feel confortable using that (42-74) needle with this temps but my question is, when the temps reach 75-85°, (the time will tell) but maybe this rich hesitation comes back, is it safe to use the 42-75 needle? i see people using the -74 needle at 80°F with success and im using it at 53°F, that confuse me a little bit. lol
thanks guys
Correct on the air screw. Measured by turns out from full in. Make sure you are counting full turns and not half turns.
The hose in the center of the bowl is the bowl overflow. It leaks from there if the bowl is getting too full from either incorrect float height or the float needle sticking open. Take the carb off, bowl off and inspect the float and measure the float height. Should be 8-9mm. Test that the float needle is closing properly and replace as needed.
Yes, try a 35 pilot.
What are your temp and elevation (I assume hot, humid and sea level in Florida)? What gas, oil, and ratio are you running ?
Yeah you should have none of that hesitation. Put in the 42-74 on clip 2. And I also think you should be getting more towards a 520 or 540 main in those temps. On my 150 I am running a 540 even in crazy hot Arizona and elevation 400M. As a tuning option, yes you can try the -75 needles. I used them in some of the 2022 125's that were prone to a roll on rich hesitation. Don't be afraid to try them.
Pit Row
I actually moved back to Indiana! Okay great I have the air screw correct. I am at average 65-80F currently and 500-1100ft elevation. I am using Sunoco 110 with Amsoil Dominator mixed at 50-1. I know the float needle works freely, but I have not measured float height yet. I bet it is set too high. I will check it. Also, when do you really know when to adjust air screw? Is there a good way to test it back and forth to see where it really wants to be?
I set the air screw by feel and ear. On my 150, I am either at 1.5 or 1.75. If that range is not enough, that is my indication to swap the pilot.
Update: now with 42-74 2 clip , is much better , im pretty happy how the bike is runnig, you can hear it from the video. Today i had a MX class, so i could test it. I notice after i let the engine idle for a few minutes, starts to sputters/ hesitate but after a few full throttle passes it clears and stays running beautiful. i will double check the float height it look like starts to load up on idle. Im with 35 PJ 1.75/2 turns AS and 1.75 PV (i dont know if less turns is more bottom or 2.5 turns from flush is more over rev) and today its more hot. aroung 65°F, here is almost spring . Cold morning 55°F and a few hours later , its like 68°F . Anyway, im pretty happy with the bike, i will check the float height but that needle is spot on !. Thanks @FGR01 , i will order 520 main and 43-75 needle for 85°F+ temps.
Good improvement. It sounds like there’s still a bit of initial hesitation. Try a 32.5 pilot sometime. Especially as it keeps getting warmer temperature.
What elevation are you riding? I've also got a 22' 150SX, just got a #5 slide. Was going to try 42-75 needle and see what happens although i am at 5k'+ elevation so I may need leaner settings. It had a Keihin on it before and ran great but now its up for sale but I need to get it running decent to sell lol.
Also I have a few JD needles laying around from carbs I bought in the past does anyone know if the JD red with 2 or 3 hash marks will work for this 150? Not sure how to tell which JD needles are for which bikes after the paperwork has been lost for years lol.
I'm at sea level so my settings probably aren't very helpful, 42-75 has been good but I may be a bit too lean
I ended up sticking with the settings I had as its been great since that day, but I found when testing the vented airbox cover that the bike ran worse, stuttered and was not running cleanly. But with the non vented cover it runs great, would this mean my settings are a bit too lean? The last I tested the vented cover was probably a bit over a month ago, and the weather has cooled down quite a bit now, typically between 55-65F. Should my settings be ok to run in this cooler weather or should I look at going richer? We only have a couple weeks of riding left here anyways, but the spring temperatures will be quite similar, and a bit colder when riding starts in April.
Better with non-vented suggests the settings are lean, but those settings aren't very lean for a 150. However, when temps start getting down below 55F I would consider a richer pilot and main, depending on what the bike feels like.
Just picked up a 2021 MC125. Bone stock and has a pretty good 1/4 throttle bog. I was ready to pull the trigger on the parts for the setup in the opening thread. JD is back ordered on the slide. I found several favorable reviews on the JD jet kit so I ordered that and a jet block gasket. I mainly want to get the bike somewhat dialed so my son can get some seat time on it in the remaining nice weather. I've seached and cant seem to find if anyone has run both the JD jet kit vs the jetting in this thread. Or if anyone has combined the JD needles with the other components. I guess I'm mainly wondering how the JD needles compare to the needle specified here.
I ran the JD kit when I first got the bike and it didn't help the issues I had, but the bike is a 250. The JD kit is a band aid for the real problem, the slide. No the needles don't work with the jetting in this thread. They are a custom taper to try and get around the rich slide.
If the stock jetting has the 42-71 needle, try putting the clip all the way at the top in slot-1. That usually minimizes that 1/4 throttle stumble fairly well until you can do the full setup from here.
Ill try that for this weekend. Do you find the recommended jetting in the manual to be close when utilizing stock carb components? We are coming off of MC85s and the recommended jetting was always a bit rich. I love the pwk carbs and am really tempted to swap this one over.
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