440 Jetting...need help please..(yeap..another jetting question)

[SLB400EX]

Before...440EX(11:1 compr), big hole in air box lid, 38 pilot jet, 170 Dyno jet, clip in third groove. Ran great, plug looked good.

Now....slightly larger hole in air box lid. Same pilot, same clip postion BUT bumped up the main to compensate for the bigger hole.
Have in a 195 now. Did a few "throttle chop" runs then just rode it around for a while. At every check, the plug looked really lean now. It's a very light gray. :confused:
W/ both the 190 & 195, there was a slight "burp"(or hesitation) on the way up to WOT.
Rob is running half Torco/half 93 octane pump gas. I know it's sometimes hard to get a true plug reading(especially with race gas) but the plug looked good b4. It was a nice coffee brown.
Honestly, we figured going that high(w/ the 195) would make the bike run like crap, make it too rich. We went that high, planning to work down to a smaller jet.... Hhmm..so much for that plan.
Thought about going back to the 170-175 but afraid that would be too lean seeing the 195 shows it to be lean.
Any suggestions here would be appreciated...b4 we go nuts.


Thanks in advance,
Sher

(jetting sucks...)

[SLB400EX]

bump

Man jetting is a big enough pain, and you go and change so many things at once you must really love the pain :devil

Lets go back to when things "felt" right and start from there.

I am assumeing a few things since you didnt detail them.

Fill up the tank with whatever fuel you were using b4 so you dont get any flawed results or reading form that, plus an honest 11:1 prob wont need much race fuel if any.

Now go back to the original MJ and settings that had worked for you b4.

Take it for a ride (not a 3 hour hard run but a short ride) and see how it responds. I am betting that the larger hole didnt require as much more fuel as you thought. Do look at the plug after a 3rd or 4th gear wot (fully pegged) run and shut it down and look at the plug. Compare the plug to what you had seen b4 the changes and try any larger or smaller jets from there.

You may want to look at the 1/4 to 3/4 (needle position) settings also and see what is happening there.

FYI the stuttering you describe sounds like too much fuel to me.

I dont understand the kehin to dyno sizes or numbers but the 195 in a keihin sounds way much for what your telling us.

And yes jetting is fun, trust me I know LMAO

[SLB400EX]

The 195 is a dyno jet. When we slapped that one in, we really expected the quad to run like crap, expected it to choke out on the fuel and we were just gonna work down from there w/ the jet sizes. Hmmm.
Rob kinda figured the hestitation meant it was getting too much fuel. It's not a huge hesitation, but it is there. Other than that, it ran good.
We're gonna work with it today. Probably tick off the neighbors again too. I got some evil looks yesterday during a throttle chop run.
:eek2:
Wish us luck.
Oohh...and we do like the pain..we re-jetted mine yesterday too, she was a lot easier though.......opened up the air box on her too. :devil NICE!!!
THANKS!! Appreciate the help.

Oh sure I figured you would be using dyno jets ;) I gave up on them and switched back to the keihins becaue of the confusion and the fact that I figured why not stick with the jets from the carb mfg etc.

Just dont forget about the needle and how the needle position circuit bleeds into the main etc. and that when you make adjustmensts to the main size it does slightly effect the needle also since the needle goes down into the main jet.

BTW did the dyno kit come with a new needle?

[SLB400EX]

Yeap..the dyno jet kit came w/ a needle and clip. He's had the dyno jet set up for a while.
I'm just using the keihin jets. ;)

Anyhow, we put the 180 dyno jet in his today, rode for a while(3miles-/+). He said the bike ran good. No bogging, no hesitation..just ran nice and strong from idle to WOT. Decided not to pay much attention to how the plug looks...just adds confusion to the issue. lol. :p
When the shop did his 440 a few years ago, they decked his cylinder so he is running 11:1. :D He's been running race gas ever since. Heard/hoping the race gas helps it run cooler, especially on those hot, hot summer days.
Hey..thanks again for the input.
We're in the process of getting these machine ready for our first trip to the dunes next month!!! Can't wait!!!! Gotta have them dialed in just prefect!! :devil

Later..Sher