jetting question

E

extreman1

New member
Joined
Feb 3, 2004
Messages
45
I have changed my main jet from 165 to 170, richer, my question is if i lower my needle's, making it a little leaner. at full throttle will the leaner needle position have any affect? or will it be no different.i know it will it be leaner in the mid-lower range.I have a 02 viper, bender pipes, since i jetted up mains I have fouled plugs after warm up almost as soon as i hit the throttle.
 

Well the fouling plugs issure shouldn't be caused by the mains...Main jets control 3/4 to WOT.
The pilot jet controls 0-1/4 throttle.
The pilot jet along with the fuel screws control the idle circuit portion of your carbs.
The needle setting controls 1/3-3/4 throttle.
Pilot is said to contribute to maybe 5% at WOT
Did you go up with the pilot jet from stock at all when you piped it??
Did you adjust fuel screws at all???
 
JohnnyQuest said:
Well the fouling plugs issure shouldn't be caused by the mains...Main jets control 3/4 to WOT.
The pilot jet controls 0-1/4 throttle.
The pilot jet along with the fuel screws control the idle circuit portion of your carbs.
The needle setting controls 1/3-3/4 throttle.
Pilot is said to contribute to maybe 5% at WOT
Did you go up with the pilot jet from stock at all when you piped it??
Did you adjust fuel screws at all???
Click to expand...

Yes pilots 55 fuel screws 17l8 turn
 
i had 165 main before and i burnt center piston at full throttle, i went up mains tp 170 to fix the lean condition at full throttle. now i am fouling plugs.
 
Your mains are fine.
Your stock pilot size is 45, and if your running 55's now that seems like a pretty big jump for a pilot.
Pipe makers' jetting is notoriously rich, to cover their *** in case of a burn down... What did Bender recommend for jetting specs, mains, pilots, needles and fuel screws??
I have Hauck (CPR) pipes on my SX-R 700 and this is what Hauck said to jet it at.....
150 mains
47.5 pilots
needle up 1 notch
and screws 1.75 out

Over time (and careful plug watching @ ALL TEMPS) I've been able to get best performance all around with this set up.....
148.8 mains
45pilots
needles stock
and screws out 2
 
JohnnyQuest said:
Your mains are fine.
Your stock pilot size is 45, and if your running 55's now that seems like a pretty big jump for a pilot.
Pipe makers' jetting is notoriously rich, to cover their *** in case of a burn down... What did Bender recommend for jetting specs, mains, pilots, needles and fuel screws??
I have Hauck (CPR) pipes on my SX-R 700 and this is what Hauck said to jet it at.....
150 mains
47.5 pilots
needle up 1 notch
and screws 1.75 out

Over time (and careful plug watching @ ALL TEMPS) I've been able to get best performance all around with this set up.....
148.8 mains
45pilots
needles stock
and screws out 2
Click to expand...


I think benders spec are: 165 mains, stock needle setting, stock needle jets, 55 pilots 17/8 fuel screws
 
you should have no problems with trying a smaller pilot in my opinion!
Maybe a 52.5 or even a 50.
Where do you ride? What temps? altitude?
 
JohnnyQuest said:
you should have no problems with trying a smaller pilot in my opinion!
Maybe a 52.5 or even a 50.
Where do you ride? What temps? altitude?
Click to expand...

ride @ 0-1500ft 0-35 degrees, also I had carbs off put back on and now when I started sled it iT RUNS REAL ROUGH back fires real high idle mostly on 2 clyinders. any ideas? I checked the floats and there ok not stuck. any chance i screwed up somthing electrical??
 
Check the throttle cable. You may have a tors problem if its to tight. Also leave the 55 pilots in there. Bender Pipes need fuel in the mid range. I would put the needles stock and 2 turns out on the fuel screws, idle set at 1800. Thats where mine is and it works perfect. 900 miles on the same plugs with 170 mains. Make sure the carbs are vented to the air box.
 
justaviper said:
Check the throttle cable. You may have a tors problem if its to tight. Also leave the 55 pilots in there. Bender Pipes need fuel in the mid range. I would put the needles stock and 2 turns out on the fuel screws, idle set at 1800. Thats where mine is and it works perfect. 900 miles on the same plugs with 170 mains. Make sure the carbs are vented to the air box.
Click to expand...

how do i check the tors? would that cause the miss firing and back fire?
 
I am just curious. I am not a seasoned tuner. What head to you have? What kind of compression? I would think you must have some pretty hefty compression or ride in really cold weather to need the 170 jets?

I have an 04 with DCS. I have the Benders, peak head with 22cc domes and stock Viper gaskets. I am 136 with a MM rear cooler. I ride sea level to about 1500ft or so. I have 165s/55s and 1 3/4 on the screws. As I recall without looking it up my clips are at 3. That was down 1 clip from where they were. I did not do benders air box mod.

When I first set mine up I did some plug chops with 170 MJs @ 20*F (-6*C). The plugs were wet. Even the 167.5s were very rich. I have a set of 162.5s and think I could run those without a problem as long as it didn't get colder. I have ridden mine at -10*F (-23*C) and not seen a flicker of the DCS light. I do not typically do very long WOT runs, no more than a mile or so. It is just way too fast for me.

Benders specs;

Jetting should be determined by the quality of fuel available in your area. For those running blended, oxygenated, or unknown fuel, 167.5 mj and 55 pj are required. Using premium pump gas of known good quality allows for 165 mj and 52.5 pilots.

A good pic of my plugs is HERE
 
Last edited:
extreman1 said:
how do i check the tors? would that cause the miss firing and back fire?
Click to expand...

Make sure the throttle cable is properly in the joint. It can slip out and catch on the cable joint. Its beside the air box on the rt side. The joint is under a rubber boot. If thats ok adjust the cable at the carbs so you have about 1/8" gap at the throttle lever. A bit looser is ok. If the tors is activated it will sound like a rev limiter, kinda what your describing.
 
JeepTherapy said:
I am just curious. I am not a seasoned tuner. What head to you have? What kind of compression? I would think you must have some pretty hefty compression or ride in really cold weather to need the 170 jets?

I have an 04 with DCS. I have the Benders, peak head with 22cc domes and stock Viper gaskets. I am 136 with a MM rear cooler. I ride sea level to about 1500ft or so. I have 165s/55s and 1 3/4 on the screws. As I recall without looking it up my clips are at 3. That was down 1 clip from where they were. I did not do benders air box mod.

When I first set mine up I did some plug chops with 170 MJs @ 20*F (6*C). The plugs were wet. Even the 167.5s were very rich. I have a set of 162.5s and think I could run those without a problem as long as it didn't get colder. I have ridden mine at -10*F (-23*C) and not seen a flicker of the DCS light. I do not typically do very long WOT runs, no more than a mile or so. It is just way too fast for me.

Benders specs;

Jetting should be determined by the quality of fuel available in your area. For those running blended, oxygenated, or unknown fuel, 167.5 mj and 55 pj are required. Using premium pump gas of known good quality allows for 165 mj and 52.5 pilots.

A good pic of my plugs is HERE
Click to expand...

I have the viper head with benders mod. The air quality is really good here at sea level. Its usually around -15 to -20c. If i go out in 0 to -10c its a bit rich. I'm running on the edge at -20 according to the plug readings. I don't think there is mutch of a gain if any going leaner so i play it safe. If your running in 6* its going to be way off with 55's and 170's especially without the air box mod. My air box is modded slightly with 3 1.5" holes in the top under the filter. I tried it with the reccomended 55 and 167.5's and the dcs would light up. I havn't seen it with the bigger jets.
 
typical ride at -15 to -20c I would move :D now that you mention it again I think I recall you saying that before. I am just getting ready to head out, and it is a typical day. About 17*F (-8*c) I see I missed the - sign on the -6*c before.

I really wish my DCS would light up one time. I would like to know that it works.

I want to get a set of TPI valves in my airbox so I can open them on the really warm days.
 
JeepTherapy said:
typical ride at -15 to -20c I would move :D now that you mention it again I think I recall you saying that before. I am just getting ready to head out, and it is a typical day. About 17*F (-8*c) I see I missed the - sign on the -6*c before.

I really wish my DCS would light up one time. I would like to know that it works.

I want to get a set of TPI valves in my airbox so I can open them on the really warm days.
Click to expand...

i ride at 0-1500ft I found my problem the tors switch under the idle adjust screw had backed
right of the screw. Can the switch be bypassed? I tryed screwing it back on but when i try to adjust the idle it just backs out again? any ideas
 
justaviper said:
I have the viper head with benders mod. The air quality is really good here at sea level. Its usually around -15 to -20c. If i go out in 0 to -10c its a bit rich. I'm running on the edge at -20 according to the plug readings. I don't think there is mutch of a gain if any going leaner so i play it safe. If your running in 6* its going to be way off with 55's and 170's especially without the air box mod. My air box is modded slightly with 3 1.5" holes in the top under the filter. I tried it with the reccomended 55 and 167.5's and the dcs would light up. I havn't seen it with the bigger jets.
Click to expand...

mine is stock except for the bender pipes, do you know if i can bypass the tors switch?
 
You must log in or register to reply here.


Back
Top