Just added the FMF Q4 and the Powerbomb. Put a new spark plug in and want to know how long to run it before checking plug color to see if the jetting is ok.

 

I'd say a few hundred miles at the minimum.

 

You're going to have a hard time getting a really reliable plug reading. Unleaded fuels, ethanol additives, and other fuel issues will seldom yield a good reading like the "old days".

 

do a Google search on plug chops, the two stroke guy do it, the same applies to four stroke engines.

 

You need a wideband meter to be 100%. Spark plug colors are too risky and primitive.

 

Here's a reference chart I found before.

https://www.kawasakiforums.com/forum...ur-plug-39758/

 

Very difficult as stated above, and if you read the plug as lean do you go up on the pilot, raise the needle or go big on the main jet as any of these will make it richer or they all will. How by looking at a plug are you going to know where you need to add gas.

 

Jetting in the modern age of cleaner fuels, many mixed with ethanol, is better done by gauging performance with close attention to throttle position. Fuel injection, on models equipped with such, make it even harder to read plugs. Performance assessment from idle all the way to wide-open-throttle is a better measurement of fuel delivery. Unfortunately this usually takes a little more experience with what the engine is doing and how each segment in the carb affects the results. Listening for detonation is important too.

 

So that being said, I just installed a q4 slip on, uni air filter, a bill blue 33-34 pumper carb with a main of 137.5 pilot 40. I went for a ride today at about 6500'. If i was smooth through the throttle to wide open it behaved just about perfectly. If I quickly go to wot, it would stutter at about 8-9. It would also stutter if I just snapped the throttle from idle. I started at about 2.5 turns out on the mixture. It got better at 1.5 turns out but wouldn't idle at 1 turn. I'm a carb newbie so would love to which jet pilot or main is responsible for what. Don't mean to hijack thread! Would love to learn some more. Forgot to mention there was significant backfire until I was at 1.5 turns out. There is still some decel popping but not excessive.

 

HEY!! Who you callin" "primitive!!??"

(Um....that be me.)