Pilot/AF screw???

[GIXXER1KR]

I am jetting my quad after the winter rebuild and am at a 42 pilot but it seems like it wants me to go lower???? When starting it with the 42 if the a/f screw is more than 1/2 way out it back fires.It seems like i should go lower!!! I still have the off idle bog too/ Im running the hrc carb settings with a 175 main!!!And a ton of mods!!!

[beany]

I'm running at 180 main in my 06. Seems big I know. Stock pilot to.

[chad502ex]

sounds lean the way your describing with back firing.... Try increasing the pilot or close the airbox to determine if choking off the intake airflow improves the situation. you could also choke it to see the effects of the choke has on performance.

NOTE: the choke is an air-enrichening circuit so pulling it will cause a leaner condition...

I prefer to go rich then lean.....

Good luck in your tuning.... also, if you find its still lean running there are smaller air leak jets you can install on the front of the carb that will reduce the amount of airflow to the pilot circuit....

Its a kinda shame to me seeing your jetting diminish your potential to completely enjoy your new build. I hope your able to work it out. Monsterous builds like yours always have a difficult time with idling when using huge overlap cams, heavily ported for mid-to-top and oversized carbs.... Don't give up.... It just takes finding the right adjustment to get it dialed in.... Admittingly, I use the dyno for tuning cause I cant tune like I can build.. hehe.

Let me know if I can help and feel free to give me a call if you need.

-chad

[d3ktrix]

When is it back firing? On acceleration or deceleration?

If ur getting a bog off idle that means ur pilot is lean.

You have Chads 43mm 07 CRF carb right?

Edit: Chad beat me to it :P

[GIXXER1KR]

It pulls really strong thru the rev range.But when i start it when it warms up it pops with a backfire and a flame.If adjust the airflow screw to almost closed its ok.i almost want to go to a 40 but after all the mods a 40 seems too small.I never heard of anyone running a 40 pilot with a nicely built engine!!!! I will get it ironed out and wont give up.Once i get it dialed in to near perfection i will have a better idea for future builds!!!!;)

[d3ktrix]

When does it pop and back fire? When its just idling? I'm guessing its when ur revving it.
But we need to know if its when ur giving it gas, or if it pops after u let off the gas.

You say the popping goes away when u turn the A/F screw to 1/2 turn out. Does the bog off idle also go away?

I'm running 178MJ / CRF Needle / 45 pilot / 50 leak. 600ft elevation.
And my carbs not bored and no port work. So you should need larger jets then me.

My friend with a full DRG build like you runs 180MJ and a 50 pilot in his CRF carb.

[GIXXER1KR]

I am running a DRG 14:1 piston,Web 943 Cam,+1 MM Ferrea exvalves,Kibblewhite intake,Drg port work and a DRG fcr taper bored carb on my 06.Right now i am at a 175 MJ,42PJ,55LJ,HRC needle and an adjustable a/f screw on 112...It runs good but it has that bad almost stalling bog when i rev it.I gotta let off and it clears up and if i get on it a little and then whack it its fine.I starts best with the a/f screw at 0 to 1/2 turns from closed.Any more it backfires when starting...!!!!:confused: The ****ty thing is the closest dyno is a 2 hour drive away and they want me to leave my bike there a couple days.Thats an 8 hour ride total!!!

[d3ktrix]

It only back fires when starting?
Not when ur accelerating or when u left off the gas?

When u have the A/F screw is 0-.5 turns out does the bog go away? Or just the popping?

You really didn't answer any of my questions the first time :P

[chad502ex]

Originally posted by GIXXER1KR
I am running a DRG 14:1 piston,Web 943 Cam,+1 MM Ferrea exvalves,Kibblewhite intake,Drg port work and a DRG fcr taper bored carb on my 06.Right now i am at a 175 MJ,42PJ,55LJ,HRC needle and an adjustable a/f screw on 112...It runs good but it has that bad almost stalling bog when i rev it.I gotta let off and it clears up and if i get on it a little and then whack it its fine.I starts best with the a/f screw at 0 to 1/2 turns from closed.Any more it backfires when starting...!!!!:confused: The ****ty thing is the closest dyno is a 2 hour drive away and they want me to leave my bike there a couple days.Thats an 8 hour ride total!!!

two things...

first:

by you closing off the improved air flow by turning in the air screw to 0.5 turn is indication that your flowing air big time being that you have ported, bored a carb, and installed a cam. Try reduce the size of the #100 slow air jet on the front of the carb to #45. These slow air jets is what governs low speed airflow through the idle pilot circuits. Sudco sells an adjustable slow air jet kit pn:021-230 and pn:021-235. This should allow you to adjust the slow air passage from #45 to #155 just by turning the screw.

second:

the WOT stab bog is from the accelerator pump not being able to supply enough fuel to reduce the immediate lean condition when the slide is popped open. The engine gulps a huge volume of air and the accel pump squirt is not enough to reduce the A/Fr. To fix the problem, you can either find the correct accel pump leak jet that satisfies all your dynamic engine condition or you can go the adjustable route. Again, Sudo offers an adjustable accelerator pump leak jet kit made by R&D that will solve your problem.


I think these two small adjustments will solve your jetting condition. Unfortunately, every engine could require an infinite combination of jetting,... Usually, I can get you close,... the remaining may take a bit of tuning from the owners since most of the time the quad is hundreds of miles away....


Hope this helps.

[GIXXER1KR]

Anywhere to get these jet kits faster than Sudco in Cali????

[chad502ex]

i'm sure other sell them, but when it comes to carb parts, sudco has it all for me.