I have noticed a little bog at W.O.T. and would like to know what others are running on their jetting. I am using a 150 main with the stock needle and pilot jet settings but I was thinking of going back to the stock 145 main. I’ve chopped the plug and it looks tan to gray in color but just doesn’t seam to have the kick. I’m going to double check the valve clearence first before doing any carb changes. What do you think?

 

Are you using Mikuni jets or Dynojets?

 

Mikuni.

 

First of all, the elev. you mention would have little or no bearing on carburetion, as it is for all practical purposes, sea level up to about 1200'
Second, NO NO don't run a leaner main jet! The gray plug you mention indicates a moderate to very lean mix. At your sea level location, you need FATTER main jetting..possibly a 155 or even 157. I'd get both and try the 157 first. Install a brand new plug to avoid a contaminated reading and do a proper test ride & plug read. If the insulator & the electrode are black or dark, drop down to the 155. Always best to go fatter to start and drop down if needed.

 

Ok, I checked the valves tonight and they are in spec. I did a few WOT plug chops and the plug was tan on the electrode and the porcelin was still white with a little tan spots. The problem is the quad is cutting out or sputtering at WOT in the upper RPM's. From what I've found this indicates a rich mixture, but I would think the plug would come out a little black if it was rich. The plug was new and the correct heat range.