Look at my jetting please-Popping on decel and on gear change

7 replies to this topic
  • Mrmonk7663

Posted June 10, 2010 - 03:57 PM


Started with a 165 main and a 72 starter jet. Bike would start but wanted to die if choke off...lots of popping when revving. So I put in a 168 about an hour ago. I switched it out for a 170 and stock starter jet. Starts easier and will idle fine with choke off now. I just took the bike for a spin for the first time in almost a year. Here are the specs as it sits

Main 170
Pilot 45
Fuel Screw-2 full Turns
Needle 4th from top JD Red
Starter jet-stock
RD Float bowl with acc pump cover and adj Pilot Screw
Pipe-FMF Titanium
Header-Stock (but will be putting on power bomb later tonight which will lean it out a bit right?)
Airbox-Snorkel removed, high flow filter

Ride-I took it up and down the street. I could only go about half throttle because of the area. The bike is insanely fast even at half throttle. The bike was revving smooth and not hiccuping as I increased throttle, but every time I shift gears it would crack and pop, and when I RELEASED the throttle it would crack and pop. So this is where I am at currently. 170 may seem large but its working 10x better than the 165 did. Now how do I fine tune to get this popping and cracking to go away. Oh, TPS disconnected too. So what do I need to do for this decel and gear shift popping/cracking?

Thanks yall.

One more thing...I have a YZ cam to install but I dont know if that will totally jack up my current jetting or not. It will not be installed for a few weeks though so that I can get used to the power the bike currently offers.

  • Mrmonk7663

Posted June 10, 2010 - 04:27 PM


Ok. I turned the fuel screw to 2 1/2 turns out....the popping on upshifting is gone now. I still have a popping on decel big time and also on downshifting.

  • Mrmonk7663

Posted June 10, 2010 - 11:00 PM


Anyone have advice? Do I need to up the pilot jet to 48 since im at 2 1/2 turns on the fuel screw and still have this popping? Or does the main need to go up further than 170?

  • Mutu

Posted June 10, 2010 - 11:28 PM


Anyone have advice? Do I need to up the pilot jet to 48 since im at 2 1/2 turns on the fuel screw and still have this popping? Or does the main need to go up further than 170?

Yep, go up on the pilot to 48. To get the right pilot jet and fuel screw setting, warm your bike up first. Then raise the idle a bit. You just want a high idle. Adjust the fuel screw all the way in, then move it out till you find the max rpm point. Youll know when you find it.

Needle position looks alright, if it pulled alright at 1/2 throttle, leave it where it is.

With your main jet, you have to test it at WOT. If it bogs, it is lean. If it studders, it is rich.

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  • Mrmonk7663

Posted June 10, 2010 - 11:39 PM


Ok, I'll get a 48 pilot tomorrow. By studdering and bogging....this sounds retarded but can you explain the difference. I kind of thought they were the same thing. Usually I associate bog with the bike falling on its face suddenly, and studdering to me is like a hiccupy hesitation where you feel power then lose power feel power lose power etc. Is this what you mean?

Anyway, I put on the powerbomb header tonight and will do some airbox mods...so I might end up having to go up on the main. We shall see. OH and one more thing...After im done setting the fuel screw do i lower the idle back down?


  • Mutu

Posted June 10, 2010 - 11:44 PM


Yep, you got it right. bog = lag. stutter = jerking, like cutting in and out.
reconnect TPS too, by the way.....

  • Mrmonk7663

Posted June 11, 2010 - 12:11 AM


I'll reconnect it as soon as I figure out how to set it. That's on the to do list. With the fuel screw adj. We were talking about...after I set it do I lower the idle? Thanks alot

  • Mutu

Posted June 11, 2010 - 03:57 AM


with the idle knob, the black one on the side of the carby. Turn it in to raise the idle and then set the fuel screw, then wind the knob back out to set the idle again.


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