Dan, you may be a little rich on the needle, causing that mid-range stutter. Check the plug reading with a long WOT pull and throttle-chop shut down. If it's ok, drop the needle one knotch and see if that helps the stutter. I went up and down from the 140 MJ at 1200'asl and ended up back at the 140 for best power on the dyno. Mixture was good there too according to the exhaust gas analyzer.
I think you're right on with enlarging the pilot jet to help with the decel popping. I had to go up on the pilot to help with that on theMikuni too. It sounds like you're close though. Congratulations.
Dyno???


Bill Dragoo
Norman, Oklahoma

 

Mike,

I didn't really see or feel that the #142.5 MJ was too rich. I did find that the #140 was sufficient, and it looked right on the air/fuel meter. Also, based upon Shadetree's advice and experiences - it feels right. I experience the stutter only once and that was after pulling the snorkle out. All other WOT runs pulled hard. I am going to put the snorkle back in though and try to fix the deaccel pop. I'm also a 5000'

Same jetting as me. You're running a Q0 needle jet too?


Bill,

Just to clarify, it the pilot air jet that I'm going to up -- not the pilot jet. My pilot jet is at #40. I did a couple of trials with the needle in lower positions (i.e. clip in the 1st and 2nd notches), and had stuttering in midrange -- the middle clip is working well. I won't go after the one time thing unless it becomes more consistent.

As for a dyno, I've never had one done before on any bike I owned. Don't know where to begin to find one. I guess calling a local bike shop would be a place to start. For me, its more of an issue of time vs. money. Looks like is could be an all day affair if dialing in the optimum jetting setup. Typically, how long and how much does this procedure take?

 

Dan,
There are a couple of approaches to the dyno. One is to simply get things dialed in as well as you can and just do a couple of "pulls" to measure horsepower, torque and mixture...to see where you really are.

The other is to buy some serious time with the shop and plan on pulling the carb a few times, re-jetting for optimum power and mixture. I've done both. It's a matter of dollars and good sense. If your bike runs pretty good through the whole range, it's fun to get a printout of the results of all your effort. That shouldn't cost much to do and a local shop should have a dyno or be able to suggest one that does. Of course, we'd all like to know the results too.

Bill

 

I'm also concerned about the knobby stock tire. I can see that this could skew the results due to less than optimum contact with the rollers? Wouldn't it be better to put on a supermoto type tire for the dyno run? ...what about using an aftermarket dual sport tire such as the Kenda Trackmaster II?

 

If you get a dyno run, definitely swap the tire. I used a Kenda 761 dual sport 50/50 tire. It has has grooves rather than ***** and makes good contact with the dyno. When I did my 2nd dyno run at the same shop same operator using the K761 vs the K760 TM-II the dyno operator said the knobbies was bouncing around all over the place. The K761 is cheap and for me it was worth the effort to swap the rubber even if it was just for a day to do the dyno run. You can bet that if I ever do a dyno run on my new bike that I'll be using that K761 tire and not the knobbie. By my guestimate based on my own before and after results, the dyno will read anywhere from 15% to 20% low with a knobbie than with a better tire.

Different places charge different rates. Each dyno run cost me $75. I think that is a bit on the high side. I've seen other people getting them from anywhere from free (they are friends with the shop owner) to $30 or $50 or so.