Need Help PLEASE-Jetting this 440EX!

[Steven]

I know this has been a beat topic, but please... I just need some general guidance.

I ran with the dynojet 185 main jet in today.

The bike ran ok. It didn't blub or hesitate anywhere in the powerband but it was noticeably slower accelerating at WOT.

My concern is that the bike didn't rev out with the same urgency it did with the 180 main.

Does this mean that I'm finally about where I should be with the main jet or am I too rich?

With the 185 ,the plug electrode is black, the arm is dark brown, and the porcelain is still white but now with a few black sooty flecs.


With the 180, the plug electrode is dark brown, the arm is dark brown, and the porcelain is white... also with some black sooty flecs.

I think this GT2 100 octane race gas is keeping the porcelain clean.

When i got too rich on my other 400EX with 93 pump gas, the entire plug and porcelsin got dark coffee looking. This gas just wont do that.

So where am I with jetting this bike?

HELP!

Steve

[josh]

are you running 100 octane all the time now, you should be if it is a high comp. but anyways, the spark plug is the best indicator, it should be just about were it is in both descriptions from the 185 and 180, does the bike take a long time to warm up, Lean jetting leads to long warmup times, surging, and balky throttle response, after it is nice and warm is it sluggish at all when you step on the gas from idle, if so it is a little rich, or does it almost sound like a small backfire and crackling when you decellerate, if that is the case then too lean, your pilot jet could be off to, what are you using on the pilot, and where is the e-clip on the main??? all these things effect the bike slightly, i would say you should just take it into a local small shop, run the bike for a few min and ask them what they think, the guys there should be able to help alot, cuz it is almost impossible to tell how to jet a bike if it isn't in person, but i hop i was of some help to you

josh

[Steven]

Josh, thank you for your help.

Yes, I am running 100 octane gas in the 440.

The bike warms up with the same speed as a stocker (normal).

There is no hesitation or bogging, but yes the bike is more slugginsh with the 185 than it is with the 180 at WOT. The 180 pulls harder and is crisper sounding.

There is no crackleing or backfireing when I decelerate.

I'm using the stock pilot and the clip is on the groove # 3 with the dynojet kit. Stage 2 calls for groove # 2 for a stock engine, but my plug was very lean looking during part throttle tests and I would get the occasional small backfire upon deceleration. As a result, I felt I needed to fatten the 'part throttle setting' with some more gas, so I richened things up after the build up.

So Josh, where am I?

Thanks, Steve

since ur running a real high octane i dont think u can really go by the plug. Put the 180 in and you should be fine since you said it accelerates better bc the 185 might be a little rich. Also since there is no backfiring its sounds like u r right on

[400ex99]

you said with the 185:

* slower accelerating at wot
* didn't rev out with the same urgency
* more sluggish

you said with the 180:

* rev's out good
* pulls harder & crisper sounding

so, i would put the 180 back in

you also said your clip is stock ( 3rd setting), sometimes
small backfire upon deceleration, thats why you richen
it up some? ( by 185 main jet)

try lowering the clip to 4th notch, this will raise the
needle, making it richer, this will help out with the
backfiring when decelerating ( you are lean in this area of
trottle) raising the main jet to 185 is richening it up, but
thats at wot perforamance.

hopes this help if i understood right. let us know how it
turns out.:p

[Steven]

Well, I figured it out.

First off... thanks, you guys have been very helpfull.

I went for a trail ride with the 185 main today and the bike ran like crap.

The engine didn't stumble or sputter anywhere but it was very slow to accelerate under WOT. If I pined the throttle at low RPM, the engine sort of had to clear its throat before it made its less than urgent climb to redline.

I think I finally hit the overly rich end of the jetting range for this bike. Funny thing is... I couldn't use the plug to tune as much as I had been lead to believe due to what I think was the race gas.

"400ex99" I made a mistake in my prior post. I did lower the clip on the needle from grove # 3 to grove # 4. Mid-throttle response stayed nice and crisp but the back fire's went away and the plug color improved.

The bike ran well with the 170 and 175 as well, so I'm not sure which to run. Guess I wasn't as lean as I had been lead to believe if the 185 was too rich.

With the 175 and a 16 tooth front sprocket, the bike accelerates at the same rate in gears 1-2-3 as my friends piped/stage 2 DS650.

With the 175 main in place the plug tip was dark brown, the arm was coffee color, and of course the porcelain was ash white. All the 180 added to the plug was a little more color and some black soot to the porcelain and the plug base. The 180 made the exhaust note a little fatter as well.

I guess I'll leave the 180 now that the weather is cooling (denser air) here in Florida and maybe run the 175 when it gets hot (thiner air).

What do you think?

Steve

[josh]

i think you are right on with the 180, and you should use whatever gives you the peak performance, and you said 180 revs out great and is responsive when you punch it, so i say you are dead on with the 180 and 4th notch, if there is very little crackling on decelleration i wouldn't worry about that too much, that just means you need to move the clip down a notch, but the way you described it sounds like the 180 is dead on, take it for a ride and tell us how it is

[Steven]

Thanks Josh. I'm rideing this weekend so, I report again after on performance and mileage.

Also, I just installed a Renthal 14 tooth front sprocket for fun.
I want to be able to rip 4th and 5th the way I do 1-2-3. I hope this does it. I'll report a top speed GPS reading as well, for I know many want to know how much top speed is sacrafised for better acceleration with the 14 tooth.

I'll report this weekend.

Thanks again fellas, Steve.

[josh]

i'm guessing about 3-4 mph, i put a 12 on my 250x, stock is 13 and it goes 50 on a flat when it was all stock, don't have a gps to tell exactly but up in the mountains without jetting it with it all stock and a 12 up front a motorcycle road next to me for about 2 min on a straight and said a steady 50, it won't sacrifice much but you will notice a diff when you hit those higher gears

josh

[josh]

ps

also alot funner cuz pics those front wheels up easier