No change in top speed? you didn't change the gearing just the jetting.

 

Those are similar to results I got. More and more in the middle and bottom. Nothing on the top end.

Thanks for sharing the results.

Let us know how the 351 does.

Suggestions? Ride it, leave it alone. Enjoy it.

David

 

Your bike will only go as fast as the motor will rev. If it will get to that point stock, and pull the stock gearing, then more power won't necessarily mean you'll go faster - but you should get to that point quicker. Now if you are overgeared and the bike can't pull itself to max revs, that's different - then adding more power will help it to get there.

 

with a difference of 1 mph on half of the test, i wouldnt say you lost anything. any number of things could cause this. air temp, bike temp, different gas, ect. if you want to get really geeky with it, now do a air filter and test, then 124 main and test. 120 should be good for bone stock, but i would run the next one up cus this bike is starved for gas stock.

 

You say you used a stage 1 jet setup so I have to assume that you bought the 2009+ jet kit. Why did you use a 120 main jet? I recall the stage one instructions calling for a 116 main. Maybe 118 but not a 120. I would say your main is rich and maybe limiting top end? Your first post said you were 100% stock right?

 

Often times, and I think a stock KLX is no different, the bike will not max out rpms in high gear. The torque & hp curves are falling from peak so you have less power at 10,000 rpm than at 8,000 rpm, and the wind and other resistance takes more power than the bike can produce, which is especially noticeable on the falling end of the power curve. If you're looking to go as fast as possible, I don't think you want a condition of max speed at 10,000 rpm, but rather max speed around the peak of the power curve (around 8,500 rpm if that's the peak for a stock machine).

HMF's dyno curves show peak HP in the 8,000 - 9,000 rpm range, then dropping off after 9,000. Bill Blue's charts on the 351 peak around 6,500 to 7,000 rpm, depending on setup.

To go fast, wouldn't you match your gears to reach peak speed around the point of peak HP? Today, my bike has 13 CS and 49 rear sprockets - my fastest speed is at the rev limiter - it's geared really low!

 

I have the 09+ kit #2152. The instructions recommend using the 120 main for level 1 (stock intake and exhost) I am 100% stock. The kit contains a 112. 116, 120, 124, 128, and 132.
I did not measure the 120 before installing it.
but yesterday did check hole diameter in the DJ112, DJ116, and stock jets. My results did not quite match the jet comparison chart. What I came up with was:
DJ 112 = .043"
Stock 118 = .045"
DJ 116 = .045"
I do not have the tools needed to measure to another decimal place, but the stock 118 was just slightly smaller than the DJ 116.
BTW, I am not trying to increase top speed on this bike, I did the WOT preformance tests as a way to quantify any preformance changes the larger main would provide.
After going through a few tank of gas and checking mpg with my present set up, I may put the stock jet back in and just run with the DJ needle, as I am happy I am no longer surging at 1/8 - 1/2 throttle steady state cruising.
Craig

 

You'd better read the directions again,

http://www.dynojet.com/pdf/2152.pdf

You're supposed to use a 116 with a stock exhaust and you keep saying that the bike is 100% stock so.....

 

Thank Highbeam. I did misread the instructions.
Since I replaced the bowl screws with Allen head screws, I my be able to get that 116 jet in without removing the carb.
Craig

 

You know swoggdog with his A/F meter will be all excited since he thinks stock jetting with an open exhaust is spot on. I used the 116 on mine and the engine runs to redline. Might get you more top end. On a chainsaw, 2 stroke, an overrich main will prevent the saw from hitting max rpm.