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When I read the jetting threads and try to go off of the popular settings that work for everyone, my bike is always way rich. I’ve tried Kinger’s setting with 40 power jet (N3EW-3) and had to go quite a bit leaner on the needle. I’m currently tuning with Suzuki needles and the standard NECJ-3 setting is too rich as well. I’m just wondering what could cause my bike to be so much different than most others. I’m pretty sure I don’t have an air leak. It’s my understanding that an air leak causes a lean condition, and that would be the opposite of my problem anyway.

 

I’m able to find decent settings but I don’t understand why I have to go leaner than everyone else at 800’. Thanks for any ideas.

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By 'rich' I'm guessing you mean spooging/fouling?  (as there can be oil rich or fuel rich conditions)

 

Apart from jetting, there are many other possibilities: 

 

-low compression

-high float level, inlet needle and seat worn

-worn needle jet 'nozzle', un-metered fuel drawn in

-worn/damaged clutch side crank seal

-wrong premix ratio for the application

-wrong type of premix for the application (high flash point racing oil in a trail ridden bike)

-wrong spark plug heat range

etc.

 

What year/model bike? and specific application (MX, trail/off-road etc.)

 

Edited by mlatour
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2003 yz250

Less than 10 hours on full motor rebuild and rebuilt carb.

Gnarly/shorty with fresh repack.

Stock reeds

RB squish .045

#8 notched slide

Float height set to 7.0mm

2* retarded timing

BR8EG

40:1 yamalube/91 pump

 

800’, 40-70*F, 50-100% humidity.

Woods only, lots of lugging

 

With N3EJ-2 I was at 175 main, 45 pilot, 40 power jet, 1.75 AS. Ran decent with this jetting. Couldn’t get it to idle at less than 2400 and not just die, but riding in the woods it pulled pretty good everywhere. One thin trail of spooge running all the way down silencer.

 

Just started fiddling with the Suzuki needles. Started with NECJ-3 with 168 main, 45 pilot, 40 power. Just riding on flat ground the pilot was decent but will try a 42. As soon as it hit the needle it just gargled and wouldn’t go anywhere. Idle was much improved with this set-up though.

 

Same deal when hitting needle while trying Kinger’s N3EW-3. I ended up at N3EJ-2 before it would run decent through the needle.

 

 

 

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Something is wrong  IMHO there is a problem with the motor like an air leak  or some type of air flow problem.

 

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How many hours on that carburetor? Carburetors can wear out and cause symptoms like you are describing. New genuine are only like $250 I believe.

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Needle, Needle jet, and slide should take care of most of the worn items in the carb besides the needle and seat,

His jetting should be very close for his elevation so it makes me wonder if something is a miss after the rebuild? 

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Needle jet,

Needle jet? Sounds like that could be the problem to me but how do you replace it?
How did the bike run leading up to the rebuild?

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I agree if the issue is in the carb a needle jet and needle would help,  may want to put a # 8 slide in at the same time :thumbsup:

I am still thinking something else is wrong, can you do a pressure test on the motor?

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Unless you are making systematic changes to the jetting it can be fairly easy to get everything out of wack to the point you are just chasing your tail. 

If you are lost for ideas go back to a solid baseline setting and start from scratch and dial things in slowly, not crazy winging it changes.  It's ok to take suggestions but not everything works the same for each bike for whatever reasons, and that's when you need to slowly try and dial in the different circuits one at a time. i have had it happen to me.  Everyone swears by a particular needle jet combination and it was garbage for me. 

I know you said you tried the popular settings but honestly i feel like the very much accepted starting point/baseline jetting settings for a basically stock yz250 at sea level is 48 pilot, 175 main and the N3EJ needle in the middle with the stock slide.   My 03 yz250 loved this setting with the JD needles, can't remember what clip i ended up on though.  

You mentioned you tried basically this and it was decent except for the idle.   Personally i would go back to this and tune from there.  Tuning out your idle issue should be fairly easy, not a whole lot to try and then fine tuning the rest from there should be fairly straight forward as well.  Maybe your notched #8 slide is causing the idle issues with these settings? 

Even on a yz250 with pipe, silencer, head mods ect... this is not a bad starting point.  It may be off but at least it is a starting point and you can dial each carb circuit in and it isn't typically difficult to figure out which direction you have to go with what.

Just my 2 cents.  You gotta start somewhere and just keep systematically trying logical changes, just throwing in suggestions and hoping one will work is a recipe for annoyance.   

 

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How many hours on that carburetor? Carburetors can wear out and cause symptoms like you are describing. New genuine are only like $250 I believe.


Can’t say how many hours are on the carb. Assuming a lot being an 03. I looked at changing the needle seat and that stuff but to my knowledge it’s not a replaceable part. Might have to bite the bullet and buy a new carb.

So is there any significant damage that will occur from running this worn out carb for a while with the leaner settings? I would just be compensating for the worn out parts, and as long as it runs clean with leaner jetting the spray should be good into the engine correct?

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A thought, is the rubber tip on the power jet solenoid valve still intact? if not it could be leaking it would most likely run  ok at wot but be miserable the rest of the time?

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A thought, is the rubber tip on the power jet solenoid valve still intact? if not it could be leaking it would most likely run  ok at wot but be miserable the rest of the time?

Good thought, if that tip came apart and plugged that spray bar it would run lean from about 1/3 throttle up. Take the solenoid off and clean that circuit. If the tip is gone, don't worry about it, it's only function is to shut that circuit at 8400 rpm's
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A thought, is the rubber tip on the power jet solenoid valve still intact? if not it could be leaking it would most likely run  ok at wot but be miserable the rest of the time?


Good thought, if that tip came apart and plugged that spray bar it would run lean from about 1/3 throttle up. Take the solenoid off and clean that circuit. If the tip is gone, don't worry about it, it's only function is to shut that circuit at 8400 rpm's


I’ll check it out and report back. Thanks guys.

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Don't feel bad. I'm in the exact same boat with my 20011. Engine set up and jetting almost identical except elevation is 1500-2300. What little I can add is the 42p is to lean. Starts to hang as the weather gets colder. 170 main is dead on. Did a long plug chop on the road and cut the plug open to verify. May even do 172-175 for insurance. It's all in the needle / needle jet / straight diameter vs clip position. I'm running NECJ -3 and its way fat in the middle. Runs strong in the woods but plug will be black, and can foul without warning. This problem is not unheard of. Keep a good log, lots of plugs, and a half clip washer for testing. One clip on these needles is a stupid large change. Just need more time for testing

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Replace your jet block gasket.  This little bastard is unique to the Keihin PWK and will make it difficult to impossible to clean up low throttle jetting.

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5 hours ago, subxero said:

Unless you are making systematic changes to the jetting it can be fairly easy to get everything out of wack to the point you are just chasing your tail. 

If you are lost for ideas go back to a solid baseline setting and start from scratch and dial things in slowly, not crazy winging it changes.  It's ok to take suggestions but not everything works the same for each bike for whatever reasons, and that's when you need to slowly try and dial in the different circuits one at a time. i have had it happen to me.  Everyone swears by a particular needle jet combination and it was garbage for me. 

I know you said you tried the popular settings but honestly i feel like the very much accepted starting point/baseline jetting settings for a basically stock yz250 at sea level is 48 pilot, 175 main and the N3EJ needle in the middle with the stock slide.   My 03 yz250 loved this setting with the JD needles, can't remember what clip i ended up on though.  

You mentioned you tried basically this and it was decent except for the idle.   Personally i would go back to this and tune from there.  Tuning out your idle issue should be fairly easy, not a whole lot to try and then fine tuning the rest from there should be fairly straight forward as well.  Maybe your notched #8 slide is causing the idle issues with these settings? 

Even on a yz250 with pipe, silencer, head mods ect... this is not a bad starting point.  It may be off but at least it is a starting point and you can dial each carb circuit in and it isn't typically difficult to figure out which direction you have to go with what.

Just my 2 cents.  You gotta start somewhere and just keep systematically trying logical changes, just throwing in suggestions and hoping one will work is a recipe for annoyance.   

 

Word.

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On 10/23/2018 at 4:16 PM, subxero said:

I know you said you tried the popular settings but honestly i feel like the very much accepted starting point/baseline jetting settings for a basically stock yz250 at sea level is 48 pilot, 175 main and the N3EJ needle in the middle with the stock slide.   My 03 yz250 loved this setting with the JD needles, can't remember what clip i ended up on though. 

Yep,  at 800feet and a cut head, that jetting above should be perfect. 

However, unless you’re running it like the MX racing engine it is, you’re going to get sponge from the exhaust, you’re just not making enough heat to avoid it. 

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I did a leak down test. No leaks. The power jet circuit isn’t clogged and the rubber tip on the solenoid is intact. I guess my bike just likes a leaner needle. Thanks everyone for the suggestions.

 

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