Still Need Some Carburetion/Jet Kit Help

[JustSomeDude]

So, after getting some over the phone advice from Jason and Nick at FasterMotorsports, I moved the e-clip on my jets (DynoJet Kit) to the 4th notch. Things were drastically improved this past weekend, but after riding up at altitude, some hesitation returned.

I've got a 2000 YZF 600R (little brother to the R6). My initial install was with the #144 jet as per the DynoJet instructions, and the eclip at the 3rd notch on the needle. This resulted in MAJOR low-end hesitation. The Faster guys recommended I try the 4th notch. This helped a ton, but as noted, hesitation returned at altitude, which still indicates a rich mixture (to me at least).

I've tweaked my A/F screws, but within the normal range I still can't get the hesitation to totally disappear. I'm hearing from other folks on another forum to try the #140 jet, but I guess I'm just wondering if anyone here in the region can attest to this before I rip the carbs out again.

There's a six pack in it for anyone willing to give up the info. I know a lot of the techs and people at shops don't like giving out the info for free - but I'm getting desperate here! :crazy:

[Knuckle Dragger]

Sorry to say but alot of rejetting the carbs is having to go in and replace jets untill you find the one that works with your particular bike or machine. When I tune up snowmobiles (they have the same carbs and set up as a bike) I end up taking up a variety of jets and keep trying untill I get the right one. The good news is once you get it figured out you can basicly just leave it alone and enjoy riding with good throttle response. I know this is not what you want to hear but might just be what you need to do. Sometimes machines can be picky as well I have had two identical sleds (same make/year/model/engine/etc) take different jet sizes. So in reality it is really hard to sit on a post board like this and say "oh yea that will do you up fine". Try the trail and error method it may suck at first but the result will be much better. Also with carbs you may have to settle for some hesitation in higher or lower altitude, it is just the way carbs work so tune the bike to where you ride the most. I have known guys that run one set of jets in town and if going to the high country rejet their bikes before the ride. Sorry so long but hope it helps

[JustSomeDude]

Thanks for the post Knuckle. I guess I'll have to start tinkering around this weekend. Hopefully I can find a setting that does the trick.

:crazy:

But does my line of thought make sense? If it is stumbling at altitude, it implies a rich mixture, right? So is going to the smaller jet going in the right direction?

[konichd]

Did you by chance gas up at the Conoco in Morrison on Sunday before we took off?

My Kawi was having a hard time starting and I found out is was bad gas from the 91 octane pump. If you did buy gas, burn it out and refill it again and see what happens.

[TT5.0]

Thanks for the post Knuckle. I guess I'll have to start tinkering around this weekend. Hopefully I can find a setting that does the trick.

:crazy:

But does my line of thought make sense? If it is stumbling at altitude, it implies a rich mixture, right? So is going to the smaller jet going in the right direction?

Your line of thinking is correct. I used to change to leaner jets in my old SRAD to go ride over trail ridge road in the summer. I'd try one step leaner, and maybe go back to the 3rd notch on the needle.

[JustSomeDude]

Your line of thinking is correct. I used to change to leaner jets in my old SRAD to go ride over trail ridge road in the summer. I'd try one step leaner, and maybe go back to the 3rd notch on the needle.

And another indicator of the rich lean... just filled up and did my first MPG calc since the jet kit install. 170 miles, 3.705 gallons on the pump. That's just below 46 mile per gallon. I was averaging close to 55 MPG all last summer, even with my higher elevation rides.

Looks like the #140 jets are my next move. What a pain in my butt.

[Bueller]

Main Jet is 1/2 to WOT, pilot circuit is idle through 1/4, Jet needle is 1/8 through 3/4. There is some overlap between the circuits. Sounds like your pilot jet is rich

[JustSomeDude]

Main Jet is 1/2 to WOT, pilot circuit is idle through 1/4, Jet needle is 1/8 through 3/4.

Pardon my ignorance... but I'm relatively new to motorcycles, and I don't understand a single word of what you just wrote.

:shock:

[MattTLS]

He's just saying that the main jet primarily affects high rpm, the pilot affects low rpm, and the jet needle affects midrange rpm. So in other words, if your problem is hesitation in the lower rpm range, either change the pilots and/or the position of the jet needles or the jet needles themselves. The a/f screw primarily affects the idle and the fuel level (float level) can affect everything.


Pardon my ignorance... but I'm relatively new to motorcycles, and I don't understand a single word of what you just wrote.

:shock: