Just went out and bought some main jets from the dealer...bought 128, 132, 138, 140 and a 142. Turns out, the beast runs great with a 142! I haven't read of anyone using this large of a jet. Here is my current setup for background: Clipped spring 1", one #4 brass spacer on needle, removed spark arrester, 142 main jet, 3 turns on mixture screw. I'm in the Cincy area (around 500ft elevation or so).

Couple questions:
1. Some of the jets I purchased have a K in front of them (assuming for Keihin jet) and some of them don't...they all look the same...are the ones without a K a different brand? Looking at the jets, they do increase in size as the numbers increase, so I'm assuming they aren't a mixture of Dynojets and Keihin.

2. I typically hear of people running a 135 or so on the main. Is it odd I made it all the way up to a 142?

3. Considering the setup I am running, what else can I do to boost the power? K&N filter? Drilled snorkle for increase airflow? Ideas?

By the way, thanks to all of those who posted in the other Jetting topics...really helped me get to where I am now. Great info...keep up the sharing!

Later

 

I run a 132 and it's a tad on the rich side in the summer, but I generally ride it in the winter. We are at the same elevation, Have you looked at the plug?

 

I checked it after initially putting the 142 in and it looked good (light tan color). I ran it pretty hard this past weekend and took it out today for a ride around the property (was only half throttle at most for most of the time). Just pulled the plug again. Still looks light tan for the majority of the plug, but is pretty black on the prong and the ceramic near/under the prong. I put some anti-seize on the threads of the plug before putting it back in after the first check. Do you think the black is from burning the anti-seize or do you think I'm running on the rich side. Like you, I run it all year round, so being a bit rich in the summer may not be a bad thing. Any ideas on how to get a true read on rich/lean? But I must say, this is the first time that I haven't had to use the choke to start it.

 

If the insulator is a *cardboard* brown, your good. The black on the plug is from being rich. The easiest way to check the main jetting is to put a brand new plug in the engine, run it wide open for as long as you can, close the throttle, shut the machine down, pull the plug. That will verify that you're checking only your main jet, as no other circuits are used under full throttle. If you're going to run it below 20*F I'd leave it, My jetting is spot on for near 10*, but with the minimal run time in the summer, I leave it at the 132 main jet and use it in the fall, so pretty much 75* to -20* with the same jetting. Sure there is a little power on the table, but if you're going to jump on and ride for a short while and let it sit for a week, It wouldn't be worth your while to switch all the time. Not to mention, those plastic clips turn into junk real fast.

 

I went ahead and pulled the 142 out and put in a 132 based on your recommendation. Didn't seem to make too much of a difference on the power...so i guess i'll leave it in. Does it make a difference that I pulled the spark arrestor if I didn't change the air filter (other than the sound). Was thinking that if I kept my current setup (with the spark arrestor removed) and during the winter, reinstalled the spark arrestor, I would run about the same fuel mixture level (since installing the arrestor should slow down the air and increase the richness for the cold weather. Is my thinking correct, or is it a pretty minimal change with the arrestor in or out?

 

I'm sure the arrestor adds a little back pressure, your thoughts are correct.