pop off questions

[DAG]

When your testing pop-off, you do manually open & close the needle to wet both the top and bottom sides correct? And when doing consecutive test, you do release the excess pressure behind the needle after the "pop". fill her back up and repeat.

Also is it normal to have readings a few psi off from the manual? I'm running 2.0 with black 80g spring and getting 18.5 psi in both setups. and the manual said it should read 21psi. Also n/s not leaking pre-pop and using a new gauge. :dunno:

Finely when she is lean down low just off idle i need to drop the pop psi, to allow more fuel?


thankyeah thankya

 

[Kennay]

I could be wrong, but it wouldn't be more fuel, it would be fuel sooner.

 

[Kennay]

And I stress the could be wrong part, as usual

 

[Kennay]

Aaaaaand, all your questions are answered in the SBN manual on pages 14-16 I'd revise my original answer to my interp. of what I just read, but then you wouldn't read it.:bananapowerslide:

 

[#ZERO]

With the diaphragm cover removed push the needle arm open and squirt some WD-40 between the N&S on each test.

If you see any bubbles or hear pressure leaking before the N&S pops, they worn out and should be replaced.

 

[Ericfox]

When your testing pop-off, you do manually open & close the needle to wet both the top and bottom sides correct? And when doing consecutive test, you do release the excess pressure behind the needle after the "pop". fill her back up and repeat.

Also is it normal to have readings a few psi off from the manual? I'm running 2.0 with black 95g spring and getting 18.5 psi in both setups. and the manual said it should read 21psi. Also n/s not leaking pre-pop and using a new gauge. :dunno:

Finely when she is lean down low just off idle i need to drop the pop psi, to allow more fuel?


thankyeah thankya

yeah... I spray some wd40 onto the needle to kinda submerge it... then I open and close it once or twice to seat it nicely with the wd40 helping.... then I set the carb cover plate back on top the carb and start pumping with the popoff tester... then when it pops it wont spray wd40 everywhere.... then release the excess pressure using the relief button on the tester

After it pops I spray a little more wd40 on if it needs it, but if its still pretty wet I just work the needle up and down to reseat it and then repeat the test again until I get a few numbers that are close enough to call it a good reading...


The reading being a little off the manual is perfectly normal... the manual is just a guideline... I had 95gram springs giving me a reading of like 48 or something and should have been 43 or something... if you are getting too high a number like that you can cut the spring down a little at a time to get a lower popoff, but in your case you're stuck with what you got unless you bump up to the next spring size... nothing to worry about being different from the manual anyways...

I would up the low jet to get more fuel down low... that is what I understand to be the right way to do it...

if you are getting the right amount of fuel, but just not soon enough then maybe lowering popoff might help? dont quote me on that one....

your popoff is pretty low... what setup are you running? I know some guys use a popoff that low... lets here what you are running?

 

[Ericfox]

95g spring should be dull silver... black is like 65g? I think... manual says I think...

 

[keefer]

yeah... I spray some wd40 onto the needle to kinda submerge it... then I open and close it once or twice to seat it nicely with the wd40 helping.... then I set the carb cover plate back on top the carb and start pumping with the popoff tester... then when it pops it wont spray wd40 everywhere.... then release the excess pressure using the relief button on the tester

After it pops I spray a little more wd40 on if it needs it, but if its still pretty wet I just work the needle up and down to reseat it and then repeat the test again until I get a few numbers that are close enough to call it a good reading...


The reading being a little off the manual is perfectly normal... the manual is just a guideline... I had 95gram springs giving me a reading of like 48 or something and should have been 43 or something... if you are getting too high a number like that you can cut the spring down a little at a time to get a lower popoff, but in your case you're stuck with what you got unless you bump up to the next spring size... nothing to worry about being different from the manual anyways...

I would up the low jet to get more fuel down low... that is what I understand to be the right way to do it...

if you are getting the right amount of fuel, but just not soon enough then maybe lowering popoff might help? dont quote me on that one....

your popoff is pretty low... what setup are you running? I know some guys use a popoff that low... lets here what you are running?

I would bend the arm a little before cutting the spring to adjust the pressure. Don't bend them much just tweak them to get the pressures even on both carbs. Cut the spring if you need a pressure that is in between springs. I agree, up the pilot jet to get the low end a little fatter. Adjust the low end screws to get the best idle. The pop off is for the transition from the pilot to main jet. If the pop is too high you will have a lean spot between 1/4 throttle and 1/2.

 

[Ericfox]

oh yeah.... forgot about bending the arm... thats another way.... I had to lower mine like 6 psi or something so I decided to cut the spring.... if anyone reads this and does end up cutting the spring just make sure you do it a little at a time and I think you put the cut end down into the hole.... it wont work as well putting the cut end up if I remember.... for some reason

 

[DAG]

i'm dumb, i was reading the notes i was taking from the past few days and it is indeed the black spring,, but black is 80g not 95 like i had in my 1st post..

but the same holds true black spring at 80g should read 21psi, and i'm getting 18.5psi solid in each. which seems to be in the acceptable range.

So eather way i'm very lean down low, my plugs were turning a maroon/red with the center still mostly white o_0.
so pop off does not affect lean/rich at all? its only an on/off fuel flow switch. got it.
then i guess the only way to get rid of low end lean is to bump up the pilot jet. i'll be giving that a try come morning...

thanks for the clarification's

 

[DAG]

The pop off is for the transition from the pilot to main jet. If the pop is too high you will have a lean spot between 1/4 throttle and 1/2.

you sure about that???

 

[DAG]

BTW: if you were wondering my setup

• LPW port on the 760 62t cylinder and 62t case
• duel mukunie AM 44s with 46 mani and cross over is epoxied
• running Prok filters with outwears.
• Moto Tassinari reeds think stock cages w/riva spacer
• running 33cc domes and dead on 180psi in each hole.
• and wamiltons modded b-mod pipe with port matching
• enhancer and lighten wheel

reasons for the change was i am coming from a set of OEM duels and now onto AM duels. both were 44's.


I was close before on my OEM's at:

Mains 100 H adj 1 turn out
Pilot 115 L adj 7/8 turn out
2.3 N/S with 80 gram spring​

currently with my AM's I'm lean on the bottom and i think I'm close "as of now" on my top.

Mains 115 H adj 1 turn out
Pilot 117.5 L adj 2 turns out and lean
2.0 n/s black 80g @ 18.5 psi​

 

[Ericfox]

have you checked out the thread on carb setups? I know its floating around here somewhere... I remember a couple dual 44 setups that might be somewhat close to yours on there...might give you some ideas.... good luck

 

[DAG]

yuppers,, even posted my setup in their

 

[cycojon]

if your running AM 44's then they have the return line restictor drilled out. are you running a restrictor somewhere in the return line? i it made a difference on mine.

i used a small piece of alum, and drilled and tapped it to accept a low speed jet and installed it in the return line before the tank. i think i used a 70 low speed jet.

just a thought for ya!

 

[Big Kahuna]

all you have to do is screw a Main Jet into the tank fitting where the return line plugs into the tank.

 

[DAG]

any main jet?
50/100/200

 

[Big Kahuna]

honestly, not sure if size really matters, thinking it more to just back up the flow so it does not pull the fuel out of the carb, keeping it fed. someone can probably explain better.

 

[Scraggly]

honestly, not sure if size really matters, thinking it more to just back up the flow so it does not pull the fuel out of the carb, keeping it fed. someone can probably explain better.

the carbs i got from bross are setup this way and i run a 70 main. he told me he used different jets to get different fuel pressure. for what thats worth. i dont know enough about them to go messing with it or understand the benefits yet.

 

[Big Kahuna]

I stuck one in years ago just playing around, never changed anything, but I had oem 38's. Heck, it may still be there!!!!!!!!!!