Jetting Help

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#1
OK I'm finally gonna get off my lazy butt and do something about my jetting. The bike is running rich so what should I do? I've never owned a bike where the jetting was a problem so I'm kinda in the dark on this, forgive me. I'm thinking drop the size of the main jet one or two sizes? I raised the needle one clip last year and that helped, but the last time I rode I fouled a plug and i'm getting really tired of cleaning up spooge. Thanks for any help. BTW, the bike is a 2000 KTM 250 EXC.

I just checked the extra jets I have and among them are a NOZG needle, a 48 and a 45 idiling jet, and three main jets a 178,182, and 180. I think what is in the bike are a 175, 42, and the H needle. Are the jets I have richer or leaner than what is in the bike?
 
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Strick

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#2
The jets you have at your disposal are probably richer than is in the bike now. The real 'key' to properly jetting that bike is single taper needles. I would get a hold of a couple of needles and give them a try. I am assuming where you are in Idaho is 'at' elevation. Therefore I would recommend -N- as your L1. The needles I would suggest are 1368N, and 1369N (CGJ) (CGK). Start with the middle clip position. You will also need to bump your main to 178 or 180. I think this should really help your issues.
 
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#3
Most of my riding is at fairly low elevation. I live at probably 1000 ft or so and most of my riding is between about 3000 to probably 6000 at the absolute most.
 

biglou

#4
IDK & STRICK-I'm at 1000' or less and here's what I'm currently running with success: 175 main, 42 pilot, NOZI needle @ second clip from the top. I noticed that since it is about ten degrees cooler now than when I bought the bike, that it seems to be running a little smoother, so when it was in the upper 90's I might have dropped both of those jets one more size.
Also-I have the CEK needle on order (back order, actually). I am anxious to see what kind of difference that makes. This is on the 2001 MXC 250.

***Spooge blow-by tip*** I finally put two zip-ties on the boot between the pipe and silencer and the splattering spooge that was blowing all over the shock spring area has stopped!! Should have done this sooner. Also, switching out to a PC2 silencer has all but stopped the spooge coming out the the back end.
 

Jaybird

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#5
Strick, would he want to bump the main up if he's already running rich?

BigLou, I think maybe you have the same amount of spooge comming out, it's just may not be getting past your packing yet. I don't think a silencer can effect what happens in the combustion chamber. Just a matter of time till the spooge starts comming out again.

IDkTm, If I were you, I'd take a good look at Erics website. Try to take in all he says about jetting. You already know that you are probably rich, so this gives you an idea of where to start. I'd work on my main jet first. Put in a new plug and maybe a main two steps lower than you have. Work on it like Eric says and then you will be closer and more in tune with what you are doing. Then move to the other circuits. Once you get a bike really running well, you will be glad you took the time to tune correctly.
 

Tennessee Thumper

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#6
Jaybird,I think strick was talking about bumping the main up if he went with a cgk or cgj single taper needle.
 
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biglou

#7
Jaybird-I don't know the specifics on why it happens, but the first ride on the brand new KTM had spooge drooling down the end of the stock "bazooka" silencer and onto the swingarm and rear disc. Once switched to the PC2, the spooge has all but stopped. There is still a small amount of spooge but nothing like before. It looks to be about average from the 2-strokes I've seen (all makes). When Agent Orange bought his 380 last year, he had the same results with the silencer swap. Not sure why, but it does help. I'm going to go on a "spooge info quest" to see if I can find out exactly why it happens and how to prevent it. I know it's been covered here before, I've just not had a huge problem with it.:)
 

Strick

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#8
Jaybird - Tennessee answered the question. When you switch to a single taper needle. It leans the top out. You must bump the main 2 or 3 sizes to get away from the lean condition on top.
 
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#9
I seem to be pretty good on top as far as jetting, but off the bottom is where it is the worst. Surges a little in first and will load up a bit if I'm poaking along. So that would be the pilot, correct? A smaller number is leaner right? I took a look at Erics website and that did help me understand a bit.

BigLou-I'm still running my stock bazooka as well. After a days ride I've usually got spooge clear to the bolt on the bottom of it. A new silencer or spark arrestor is definitely something I need to get. I'm thinking about maybe with just a silencer and then using the stock arrestor when it is needed or just going with a FMF TC2. Has anyone cut down there stock arrestor like what Mike Lafferty runs?
 

Strick

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#10
Your jetting on top should be fine. Triple taper needles do not seem to hamper performance on top with the right main jet combo. Keep posting your results. I want to see if you can get rid of the low end issues, and eliminate spooge with those triple taper needles. I can't!
 
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#11
Thanks Strick you make it seem like a lost cause, LOL. I'm gonna go up to the dealer tonight after work and pick up some jets and get this project under way. Spooge Be Gone!
 

Jaybird

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#12
Ok, the needle thing makes sense to me.

On the silencer...I changed my silencer from the stock to a PC early in the year. I noticed my stock silencer was completely nasty inside. Of course I had been experimenting and I expected to see alot of spooge, but it was unbelieveable. After I got my jetting worked out and put on the new PC, I saw almost no spooge for awhile. I then noticed a bit was starting again. I repacked the silencer. What I found was the original packing in the PC silencer had a hole blown in it. It was about half the way down the pipe and I could see where the hole was allowing the exhaust to go where I'm sure it was not meant to. Spooge was collecting heavily in one area. The new packing seems to have stopped it again, but I'm thinking that I still have spooge, I'm just not seeing it exit yet. Perhaps fresh/frequent packing is the answer....I plan on repacking often anwho. BTW...I get a 4" x 40 ft. roll of packing from Home Depot in the ductwork section, $1.50 a pop.:D
 

biglou

#13
Kinda freaky!

Jaybird-Believe me, I'm not trying to start an argument here, and I'm not doubting your word. BUT! What puzzles me is how after one ride with the gigantic stock silencer there can be spooge all over the place but with the much smaller PC2, there is virtually none. That is just odd. There has to be some scientific forces at work here. I still haven't done the search to find out, like I said I would :o but I sure wish I knew why! Trust me, if I find out, I'll share!:)
 

Jaybird

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#14
LOL, I have nothing to base an argument from. Like you, I too am a student of bike tuning.
I do know that spooge is unburnt oil that has condensed back to a liquid state. Perhaps the length of the silencer has something to do with why we see more of it from a long torpedo. Maybe it has more of a chance to condense before it exits? :think Hmmm.....

So many factors involved in the making of spooge, it's hard to pinpoint how to get rid of it. I do know that if I'm on the pipe hard for the whole ride, I have LOTS less spooge on the back of my number plate that if I'm poking around in the field with the kids. BUT...I'm premixing 20:1 and I went to a 7 plug. I seem to be jetted/mixed/plugged/timed spot on for full on racing.

ps...I'm fairly convinced that the flash point of the oil used is a big contributing factor.