i looked through the threads for this set up but no one had it, so heres my question. Stage1 hot cam with a ported and polished head, hard style k/n, stock pipe w/ end cut off. 195jets in both carbs, no lid. have no power past 3000 to 4000 rpm. Just spit and sputter.

Would this possibly be necessary to rejet.

This set up minus cam and head ran like a champ. I could pull 95+ mph on 20in tire and 15tooth sprocket. Yamaha dealer rejeted for this set up and i ran like a bat out of hell. power all the way through the throttle.

i would have thought that the jets would have been good for this cam, but i dont know if it would be too much air or too much fuel.

I realize that there a lots of questions about cams and regeting, but i trying to find knowledge for this particular set up.

The cam and head cam from an 02, that out pulled me hard with stock intake, stock muffler, supposedly stock jets, but with a 13:1 piston.
Im really asking if im just stupid or would this setup need a little attention to the jetting

 

Make sure it's not the parking brake or revese rev limiters.

It could be something plugged up in one or both carbs. Mine was doing almost the same thing a few weeks ago and it was a plugged high speed air jet in the right carb.

If those things are good I would check and make sure the cam is timed right and the decompression mechanism is installed right.

It could be jetted to rich but if you was using the same jets before it seems that it should be close enough now to run better then what it is.

 

In general, if jetting is off you will be down on power. Rich jetting causes sputtering & takes a long time to reach max speed or full throttle response if ever. If way too rich, it will almost shut off/lunge when asking for throttle.

Lean jetting causes a slight hesitation that may not be noticeable until you are way too lean in which you may still have decent throttle response but the power will die off considerably with increasing throttle. Lean jetting on the low end will result in back firing out of the tail pipe.

With a stock cam & no head work & no lid & approx 1k elevation, I ran 160/165/170 mains. Currently I have a 102mm 12:1 piston, s1 cam, & major head/valve work & I run 190/195/200/205 mains depending on temp/humidity.

Something that I have learned regarding jetting the cv style carbs is that any temp/humidity change requires a jetting change to make max power. I used to rejet all the time until I discovered oxygenated race gas. Mix a little in with your pump or high octane race gas & it leans out the jetting. Run it straight & it requires increasing the mains by 3-4 sizes & 1-2 clip positions.

Typicaly I jet on the rich side & then mix in some oxygenated race gas until it leans out the mixture. I still have to make jetting changes from winter to summer but in between I just alter the amount of oxygenated race gas that I add. It costs between $10-$15 bucks a gallon but saves a lot of time/patience dealing with jetting problems.

 

I had the problem too for months ago, try to change your spark plug before you do anything complicated.

 

Thanks, ill try cleaning the carbs before i start throwing off the jets. i appreciate the input.