Need advice...Am I going in the right direction?

A reference for the PWK carbs...
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Buck Nasty
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Need advice...Am I going in the right direction?

Post by Buck Nasty » 12:03 pm Nov 02 2017

Hey gang. Doing my best to dial-in the jetting on my '00 200. I live and ride in the high desert (relatively low humidity), ranging from 3,500-5,500ft typically. I love to let 'er rip but, I also have to keep pace with a 6 year old on a 50. When I got the bike 2 months ago, the thing lacked the snap my buddies 200 had. The bike came from a lower elevation so, I figured it was likely jetted fat (didn't foul a plug with that jetting but, the ride was cut short due to a clogged petcock 17 miles). Opened it up and found a 158MJ, 48 pilot and running the 3rd clip on the stock needle. After getting some info from multiple sources, I dropped the main to a 150 and the pilot to a 42 (left the clip alone). What a difference! Felt a little fat in the mid-range but, it seemed to rip pretty good. Runs super clean once you hit that last 1/3 of the throttle. Keep in mind that one trip after the new jetting the temps were in the low 50's @ 4500ft and low 50's and high humidity @4500ft. No problems. Then, it got warm. 20 degrees warmer. Took it for a ride at 70F @ 3,000ft and by 20 miles I had fouled a plug. Lower speed, techy stuff. I never messed with the pilot screw to adjust for the change in conditions. Lastly, went back to 4,500ft at about 65F and fouled a plug at 16 and 21 miles respectively. I adjusted the pilot screw for the conditions and did my best to not lug the bike so much. Sorry for the long winded post but, I wanna give as much background as possible.

Now that we're heading into winter, those 65-70 degree days are gone so, that will play a factor in jetting. I was gonna drop the clip one spot to try and clean up the mid-range. Could my pilot be too rich still? I want to make sure my thought process is correct. What would be your next step? My MAIN goal...Not to foul a plug!

2000 KDX200
Snorkel removed
FMF Gnarly pipe and silencer (Not sure the specifics on models)
150MJ (Was 158)
42PJ (Was 48)
3rd Clip stock needle
3500-5500ft
Low Humidity
Temps 40-55F (Now) 70-90F Summer
Premix: 50:1-48:1 Klotz Full-Syn
Plug: BR8ES

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Julien D
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Re: Need advice...Am I going in the right direction?

Post by Julien D » 02:32 pm Nov 02 2017

Well, throwing jets at it in a trial and error sort of way is certainly one way to go about it, although not the proper way.

http://www.kdxrider.net/forums/viewtopi ... 105&t=1156

The best thing you can do is to follow that guide exactly. I'd also never run 50:1 in mine, but that's just me. Well, just me and a whole lot of other people, lol. The manual calls for 32:1. I am jetted for 40:1 and so that is what I run all the time. Definitely settle on a ratio and stick with it. Changing your oil ratio WILL throw off your jetting. To a large extent, more oil is always better for performance.
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Buck Nasty
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Re: Need advice...Am I going in the right direction?

Post by Buck Nasty » 04:45 pm Nov 02 2017

Julien D wrote:Well, throwing jets at it in a trial and error sort of way is certainly one way to go about it, although not the proper way.

http://www.kdxrider.net/forums/viewtopi ... 105&t=1156

The best thing you can do is to follow that guide exactly. I'd also never run 50:1 in mine, but that's just me. Well, just me and a whole lot of other people, lol. The manual calls for 32:1. I am jetted for 40:1 and so that is what I run all the time. Definitely settle on a ratio and stick with it. Changing your oil ratio WILL throw off your jetting. To a large extent, more oil is always better for performance.
I've also heard from equally as many 2 strokers say to go off what the oil mfgr states to mix at. Also heard that you don't wanna run full-synthetic premix at the same ratio as dino premix. I had a 01 CR250 that I ran at 50:1 full syn with no issues. I understand the rich/lean concept with premix ratios and don't have an issue running more oil. However, running less oil and the engine getting enough lube is good for the wallet too.

Maybe I can compromise and run a 40-42:1? I'll re-start the process there.


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Buck Nasty
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Re: Need advice...Am I going in the right direction?

Post by Buck Nasty » 04:51 pm Nov 02 2017

Funny, according to that post, throwing jets at it is the way to do it. I'm just trying to work in the right direction. Not get specifics necessarily. I understand that there are a lot of variables.

"Are you fouling plugs? Many people will tell you all sorts of band-aid fixes, 

from running less oil, to running a hotter plug. Both are incorrect fixes for plug fouling. It's all in the jetting.


The only way to know what jetting changes you will need is by trial-and-error. No one can give you jetting specs, because every bike is different, 

every rider has a different style, and jetting is totally weather dependent."

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Re: Need advice...Am I going in the right direction?

Post by SS109 » 09:22 pm Nov 02 2017

Buck Nasty wrote:Funny, according to that post, throwing jets at it is the way to do it.
To a degree, yes, but it is a systematic approach so you are "throwing" less jets at it.

Going off the top of my head I would say your pilot jet is still fat. I think I'm running a 38 year round and ride 2000-4500ft most of the time. The pilot jet is really easy to figure out if it it's right or wrong and which way you need to go with it if you follow the jetting guide. From there it gets more involved with doing multiple plug chops. Once you have it figured out (you do log everything, yes?) for your given parameters (altitude, humidity, etc) you can figure out which way to go with it when any of those parameters change significantly.
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Buck Nasty
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Re: Need advice...Am I going in the right direction?

Post by Buck Nasty » 09:49 pm Nov 02 2017

SS109 wrote:
Buck Nasty wrote:Funny, according to that post, throwing jets at it is the way to do it.
To a degree, yes, but it is a systematic approach so you are "throwing" less jets at it.

Going off the top of my head I would say your pilot jet is still fat. I think I'm running a 38 year round and ride 2000-4500ft most of the time. The pilot jet is really easy to figure out if it it's right or wrong and which way you need to go with it if you follow the jetting guide. From there it gets more involved with doing multiple plug chops. Once you have it figured out (you do log everything, yes?) for your given parameters (altitude, humidity, etc) you can figure out which way to go with it when any of those parameters change significantly.
I'm logging it in my head now but, as I get deeper, I will notate. Pilot screw will kill the bike (or close) inside of 3/4 of a turn. I can turn it all the way out with little to no change.

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Re: Need advice...Am I going in the right direction?

Post by bufftester » 10:20 pm Nov 02 2017

IF you're following the jetting guide fully, you aren't throwing jets. Start with your current setup and tune the pilot circuit. There are 3 outcomes - 1 no change, 2 need smaller pilot, 3 need larger pilot. Put in the next larger or smaller side based on those results and redo the pilot circuit tuning. Once that is good move to the next. Quite simple process as long as you change one thing at a time, don't skip around. Jetting is dependent on many variables. Pick an oil, then don't change it. Pick a ratio, then don't change it (doesn't matter if you go 32, 40, 50:1, just pick one and stay with it). Before you do any of that, make sure the intake and exhaust tracts are functional and mechanically sound. Always start with clean filter, fresh fuel, new plug. Yes it takes time, yes it uses up a bunch of plugs, and yes it works every time.

All that said, it sounds as if your PJ is too large. Remember that the air screw is adjusting air upstream of the fuel. Since turning it all the way out doesn't change anything it means your pilot circuit is way rich.

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Re: Need advice...Am I going in the right direction?

Post by John_S » 05:59 am Nov 03 2017

On both my PWK 33 & 35 I had better results with the float height at 18mm rather than 16mm. On my 35 air striker, I went all the way down to a 35 pilot jet and was still too rich when the float was at 16mm.

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Re: Need advice...Am I going in the right direction?

Post by david » 07:36 am Nov 03 2017

John_S wrote:On both my PWK 33 & 35 I had better results with the float height at 18mm rather than 16mm. On my 35 air striker, I went all the way down to a 35 pilot jet and was still too rich when the float was at 16mm.
I found that my float was resting on the carb body at 16mm, so I was not getting an accurate measurement. 18mm was the way to go for me too. One indicator that the float was off was that the idle would increase as soon as I turned off the petcock.
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Buck Nasty
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Re: Need advice...Am I going in the right direction?

Post by Buck Nasty » 09:26 am Nov 03 2017

Thanks for the info guys! It sucks that the weather won't stay consistent. Near 70 last Saturday. 40 tomorrow. Ugh.

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Re: Need advice...Am I going in the right direction?

Post by tman » 11:01 pm Apr 16 2019

Fuel/Oil ratio is determined by what oil your using. Not just factory recommendation. I use Golden Spectro at 52:1. As recommended by Jeff Fredette.

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