bike running the same with JD jets

alright so ive got a 09 sm with rs4 pipes i bought used. PO had not jetted the bike but did the 3x3 mod. when i got the bike it backfired like crazy (shotgun backfiring) on decel, reving, all that. it also started up without the choke when cold. i played with the a/f screw before jetting and turned it in just a bit and it stoped backfiring on decel, but then it started backfiring whenever i left off throttle from 1/2-3/4, so basicly when i upshifted or just roll off the gas.

 

now i have a jd jet kit installed and its still doing the same exact thing. i feel like the powerband is a little more smoother overall but it still cranks over cold with no choke easily, and pops when rolling off the throttle.

 

specs are 300 ft elevation

160 main

blue jd needle 3rd clip

25 pilot

2.75 extended fuel screw

3x3 mod

rs4 yoshi pipes
 

carb was completely stock before jd kit

 

anyone with rs4s tune their bike? seems like its running rich on pilot and maybe a tad lean up top. inputs?

alright so ive got a 09 sm with rs4 pipes i bought used. PO had not jetted the bike but did the 3x3 mod. when i got the bike it backfired like crazy (shotgun backfiring) on decel, reving, all that. it also started up without the choke when cold. i played with the a/f screw before jetting and turned it in just a bit and it stoped backfiring on decel, but then it started backfiring whenever i left off throttle from 1/2-3/4, so basicly when i upshifted or just roll off the gas.

now i have a jd jet kit installed and its still doing the same exact thing. i feel like the powerband is a little more smoother overall but it still cranks over cold with no choke easily, and pops when rolling off the throttle.

specs are 300 ft elevation

160 main

blue jd needle 3rd clip

25 pilot

2.75 extended fuel screw

3x3 mod

rs4 yoshi pipes

carb was completely stock before jd kit

anyone with rs4s tune their bike? seems like its running rich on pilot and maybe a tad lean up top. inputs?

backfiring like a machine gun. Timing is out on the cams.. Mine did it and it qas set one pin to close and its sound like a new war going off in england haha now its fine :D

you have the main jet in the wrong spot

backfiring like a machine gun. Timing is out on the cams.. Mine did it and it qas set one pin to close and its sound like a new war going off in england haha now its fine :D

yeah it was but it stoped when i turned the fuel screw...i will check it tonight as i still have an auto tensioner

you have the main jet in the wrong spot

no its in the right spot

yeah it was but it stoped when i turned the fuel screw...i will check it tonight as i still have an auto tensioner

no its in the right spot

lmfao have the main jet in the wrong spot this guy has no clue. Dude

you have the main jet in the wrong spot

 

Yes, don't put the main jet on your forehead.....

lmfao have the main jet in the wrong spot this guy has no clue. Dude

Yes, don't put the main jet on your forehead.....

I cant tell if you guys are talking to me or dub lol

back firing can be from an air leak at either exhaust or inlet

 

check exhaust joint (both at head and front pipe/silencer) and also the carb to head  rubber boot

back firing can be from an air leak at either exhaust or inlet

check exhaust joint (both at head and front pipe/silencer) and also the carb to head rubber boot

not as bad as what he is saying. An out set cam makes these syptoms

Whats the condition of your ACV diaphram rubber? F/S should be closer to 2-2 1/4 turns out. Try the 155 main. Is the little tiny o-ring still there and in place? Don't change the cams...yet! Did you clean the carb and its journals really really good??? Is the float set to 9mm? Just lots of stuff to be sure of.

Pay no attention to the naysayers and their negative input. Do you know if the cams have been changed out or messed with? If not leave them be for now. Be sure you have the front of the carb rubber boot on and clamped correctly. Also the back of the carb air box boot. What kind of air filter do you have in it? Is it a proper 3 x 3 air box cut out mod? Do check to make sure the exhaust header is well seated and tight. Are all the vacuum lines correctly attached to the carb? All of these things are to make sure all is right with the carb and mounting. A process of elimanation...till you are happy with the way it runs.

not as bad as what he is saying. An out set cam makes these syptoms

 

i believe the carb boots and exhaust seal are good....i will check the cams first thing when i get home from work just to make sure its timed right and take it out of the equation and ill be able to check plug gap and burn.

 

 

Whats the condition of your ACV diaphram rubber? F/S should be closer to 2-2 1/4 turns out. Try the 155 main. Is the little tiny o-ring still there and in place? Don't change the cams...yet! Did you clean the carb and its journals really really good??? Is the float set to 9mm? Just lots of stuff to be sure of.

 

diaphrams mint... i could try 155 main but if what everyones saying is true and it only kicks on at WOT then im not using it when im rolling off the gas. O rings are all there for sure. i didnt clean the carb at all as it looked nice and clean already but maybe a cleaning in the future. float i didnt check but in theroy it should be in the right place. when i bought the bike the carb was untouched and the only thing i didnt was drill out the fuel screw and change jets/needle.

 

the thing that gets me is that it seems to run rich at idle, but the jet kit didnt change anything execpt for smoother powerband.

Did you drill your slide? Have you set the idle and air fuel screw up for max vacuum? Bike is new to you and I can see you have a good idea of what you are doing. You will eventually find and fix the problem. The JD jet kit has some good instructions. But setting the a/f screw and idle is somewhat tricky. A little decel pop and gurggle is okay. Really loud pops or machine gunning is bad.

 

As for what everyones else is saying take it with a grain of salt.  Including me. Tune in to what the experts are saying. Peeps like Eric Marquez and Noble.

Check the header pipe to engine joint and the mid pipe joint. Air leaking in there will cause backfiring. Confirm your pilot circuit( check the FAQ's)

Pay no attention to the naysayers and their negative input. Do you know if the cams have been changed out or messed with? If not leave them be for now. Be sure you have the front of the carb rubber boot on and clamped correctly. Also the back of the carb air box boot. What kind of air filter do you have in it? Is it a proper 3 x 3 air box cut out mod? Do check to make sure the exhaust header is well seated and tight. Are all the vacuum lines correctly attached to the carb? All of these things are to make sure all is right with the carb and mounting. A process of elimanation...till you are happy with the way it runs.

okay just leave then alone and wreck the engine. Most important part of the engine. Its worth a look if anything. All his jetting is correct. i basically run the same jetting. Accept im 600 ft. Mine runs fine. Its was down to the exhaust cam

Better he leave the cams alone if he does not know how to adjust them. Better to find out if they have been messed with first. If he can do all that needs be done correctly to adjust the timing of the cams he is most certainly welcome to do so at his risk. He was asking for help with the carb jetting and was given some suggestions. Not the cams. Back firing is not always the cams or timing. Sort out the carb and if still bad then look further into the timing if it wasn't messed with. If the cams and timing were tweeked then by all means check out clearences and timing.

Wait, is it correct to use the extended fuel screw with the 25 pilot?

 

I think the theory goes that the extended fuel screw is a little differently shaped, so you use the stock 22.5 pilot jet with it.

 

Source that supports it: http://www.thumpertalk.com/topic/827197-09-drz400s-yosh-rs2full-3x3-jd-jet-kit-ext-fuel-screw/

 

(Then the 4th clip is often used in circumstances such as you are in, OP - I'm not sure when to and when not to. I tried 4th in mine and it was pretty good - a little more noticeable snap/thrust. Edit - 4th vs 3rd clip is not going to make a difference to the faulty runnig you have now! It's just sugar on top when it's right.)

 

And by all means do spend time in fine-tuning the fuel screw when everything else is about OK! It makes a difference!

Edited by Anthon Berg

it could happen, just saying, the main jet and starter jet are side by side, same size, same thread, if you a person wasn't paying attention it could happen....just a thought, didn't mean to rustle jimmies.

Edited by dubweiser
25 pilot

2.75 extended fuel screw

2.75 turns are for the stock screw. with the extended screw try 1.5 turns and report back

Anthon the 25 paj is fine because of the rs4 and a/b mods.  It comes with the JD kit and is all part of the JD engineered jetting for the bike/carb. The extended fuel screw (Keintech) is what JD sells and is a match to their jetting. The lenght of it has no effect on its use. Just easier to access and adjust. Yes the f/s is diff than stock but better. Changing the clip position on the needle may help. But to many adjustments at once can throw you for a loop trying to figure which change was in the right direction or the wrong one.

 

Dubwieser. Your input is valid. Just not well explained to the noob working the problem out in that post. Perhaps said as a request to check it for that reason would have sat better. Those posts just appear as ridicule rather than help.

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