My opinion of the 84 KX jug versus a ported 85 Tecate jug.

[fabiodriven]

I have no idea who ported my Tecate jug. It was on the machine when I got it about 7 years ago. It ran for 6 of those years in my possesion with the original 25 year old Nikasil and a Wiseco piston that was also in there from the previous owner. Not much could keep up with it in a straight line. It wasn't undefeated, but if I got the jump it was over. Not only was it a killer drag machine, but I could lug the hell out of it. I used to chug up big sand pits and tight woods trails with the thing just above an idle. I could speed up if I wanted to just by rolling the throttle on. It never got loaded up on low RPM trail rides.

This past fall I put on a NOS 84 KX250 jug and a Wiseco piston. I had to fatten up the jetting a bit to get it to run right, which I had kind of anticipated. It has good power, but I'm not impressed. It has that "light switch" power band now which doesn't make the power very useful. If it packed a huge punch I would take the sacrifice of the lower end being gone, but that isn't the case. I'm fairly positive my ported Tecate jug not only had much better low end power, it also packed a better punch on top.

I've always liked the "light switch" effect of two strokes to some degree, but this power delivery is not right for most of my riding. I can see where it would be useful on a bike though. I think the engineers had the right idea with the porting on the Tecate jug. It just needs to be opened up a bit (by a professional).

One thing I have to do is a little more work with the jetting. I ran this thing all winter with my winter (fat) jets and that obviously makes a difference. I also need to dick around with the pilot. I figure I'll update after that.

[ironchop]

sounds like it made for a great trail machine and close-course warrior

A bit off topic but along the same lines.....

So how much do the differences in expansion chamber design affect the powerband?

I`ve been reading up on two smokers and I keep hearing about pipe design changes that change the way the powerband delivers to the rear wheeels (i.e. either "snappy" or "broad")

I`m trying to figure out just how many different modifications can be done to affect the powerband itself and not so much the overall horsepower rating (because I`m looking for a Green one next go-round. I want a T3!) and so far I`ve read that beside porting, the pipe (expansion chamber) can have an effect on how the powerband behaves. (specific to Kawasaki)

Your insight is appreciated

[3Razors]

Fabio, you will need a 38mm carb and open type air filter to let that cylinder make the serious topend power it was designed to. You won't see much of a gain without them. Get the Mikuni 38TM and setup per instruction in Jimmy White manual. To pick up some of the lost lowend have the head milled slightly and run race gas.

The light switch feel will still be there no matter what though..this is why later on in 1986 Kawasaki went with the powervalve design to close off the extra eye-brow ports for more lowrpm grunt.

[hang&rattle]

Great topic fabiodriven. This is something I really wanted to learn, without expensive experimentation and trial. cr480r and 3Razors, thank you. Your're information is a proof-reading in the info guessed in my brain. I always wondered, mostly for simplicity, if the stock cylinder was ported, would the power be likened to my riding style more than the KX? Answered! My terrain is similar to fabiodriven's. Lot's of moiture also, so the airbox is a must. Tight trails, but then quads to drag on the back side of the lake. Also, the low snort powerband of the DG (I know fabiodriven, I know) must be right for my elevation and riding style (fabio don't like the DG, lol), but the DG is an older one, so possibly a little different than the newer performance ones (?IDK). I also am running a stock carb, but been waiting for the right knowledge on the perfect carb. You folks information has added to my research into the 39mm airstryker. It's a mid to high end carb, thank you guys, thanks.

[HuffieVA]

Fabio,
After a year of searching, my NOS cylinder should be on its way to me as we type... I'm very interested in your results with different jetting/carb combinations, and I'll be happy to share my findings as well.
Also does anyone have any recommendations for someone still out there with the ability to properly port the KXT cylinders? Or any info on their cylinders... photos/diagrams/rubbings of the cylinder wall etc, with some more info I would consider giving it a shot on an extra sleeved cylinder, but I would really like some info first rather than full blown trial and error...

[fabiodriven]

sounds like it made for a great trail machine and close-course warrior

A bit off topic but along the same lines.....

So how much do the differences in expansion chamber design affect the powerband?

I`ve been reading up on two smokers and I keep hearing about pipe design changes that change the way the powerband delivers to the rear wheeels (i.e. either "snappy" or "broad")

I`m trying to figure out just how many different modifications can be done to affect the powerband itself and not so much the overall horsepower rating (because I`m looking for a Green one next go-round. I want a T3!) and so far I`ve read that beside porting, the pipe (expansion chamber) can have an effect on how the powerband behaves. (specific to Kawasaki)

Your insight is appreciated

I run a CRF pipe and silencer. The only other pipe I have ever run was a DG and like Hang said, I wasn't a fan of it. It seemed to kill my lower end and not do anything good on top. I never ran the DG with the KX jug though, and I didn't mess with jetting to correct anything. I just needed a spare pipe while I was repairing my CRF pipe at the time.

I have never run a stock pipe or silencer, but you can plainly see how restrictive they are.

[fabiodriven]

I suspect the jetting as the cause for the lack of top-end.. the advanced port timing and un-valved subs are obviously gonna hurt the low-end, but the carb can make things worse than they need to be.. Are you still using a stock carb Fabio?

I am running the stock carb, and that is a good point.

[fabiodriven]

Fabio, you will need a 38mm carb and open type air filter to let that cylinder make the serious topend power it was designed to. You won't see much of a gain without them..

Another good point. Like Hang said though, I have to run an airbox here. Lots and lots of mud and puddles where we roll. I could always drill some holes in an airbox I suppose.

[fabiodriven]

Also does anyone have any recommendations for someone still out there with the ability to properly port the KXT cylinders? Or any info on their cylinders... photos/diagrams/rubbings of the cylinder wall etc, with some more info I would consider giving it a shot on an extra sleeved cylinder, but I would really like some info first rather than full blown trial and error...

I don't know who did my jug, but there are plenty of experienced porting guys out there. I wouldn't try to do it myself. Everything I see says that only a true experienced porting guy is going to be able to make more power and do it right. I could try to get some pics of my Tecate jug up if you wanted to see it.

[hang&rattle]

Another good point. Like Hang said though, I have to run an airbox here. Lots and lots of mud and puddles where we roll. I could always drill some holes in an airbox I suppose.

Fabiodriven- Mark Thurman with that open billet air box cover. I oiled my new UNI filter in the box and (I know this is sorta cheesy) but threw a ziplock baggie over it in wet conditions, heck the baggie is stored right in the air box, lol. This'll give a bigger carb more room breathe. In the winter, however, run the stock or full Mark Thurman cover, to cold, too lean.

[dcreel]

My Klemm Research ported KX cylinder uses a 38mm Mikuni flat slide bored to 41mm that came with the Klemm "national kit". When you were talking about your old ported cylinder it sounded like you were talking about this Klemm ported KX cylinder. I can putt around the house giving the kids rides, and anytime I want to wheelie, slide, etc. just roll the throttle.. It just pulls and pulls.. The 85 I had had a sleeved KX cylinder that was hogged out with my 41mm carb and the Motoplat ignition.. It was a light switch with a +2 goosing the throttle it would try to throw you off.. I consider my Klemm bike fast, this I had 85 ported by Bob Troxell was damn near too fast.. It took too much concentration to keep it from spitting you off.. The powerband just "hit" and if you weren't holding on it was all over.. It was in a flat track Tecate I traded for a done up 110..

[ironchop]

Fabio....any chance you took pics of the insides of both those jugs while they were off?

While I don`t pretend to want to shadetree hack a port job on a jug myself, I would be interested in seeing the differences.

And also a bump for a well-thought technically-involved thread.

I am TOTALLY interested in jug porting technology that tames the switchy power down a notch to increase low-speed controllability

[TecateDan]

I've inherited both of fabios Jugs and was curious how you ever made out with the jetting on your KX

Fabio,
After a year of searching, my NOS cylinder should be on its way to me as we type... I'm very interested in your results with different jetting/carb combinations, and I'll be happy to share my findings as well.
Also does anyone have any recommendations for someone still out there with the ability to properly port the KXT cylinders? Or any info on their cylinders... photos/diagrams/rubbings of the cylinder wall etc, with some more info I would consider giving it a shot on an extra sleeved cylinder, but I would really like some info first rather than full blown trial and error...

[nd4speed]

Not sure my opinion of this will help much but I did a KX250 transplant sleeved with 38mm VM, KX flywheel, DG or Cobra pipe, air box lid off. Never rode such a short "light switch" on or off powerband before. It was a high rev ride, which was fine for me because I was riding it in the winter on snow and ice. Going around 65 MPH on ice with the trike shaking was more like scary fun.

I didnt hardly ride the original motor with KX ignition just before I sold it but I remember it having more low grunt as I was riding on a snowy paved street pulling up the front and thinking I was going to rip the studs out of the tires. The guy (Karl) who bought it was from OH and claimed to won some races down there with it. IDK??

So basically the KX setup was a wide open throttle, wheel spin thrill ride that was best suited for sand or snow.
Compared to other machines I have ridin over the decades, the top end power/pull on that motor was great.

[TecateDan]

So it would be a great ice racing motor but not good for trails in your opinion..