Help with intermediate jetting info

[bdmridgeback]

All I was saying is if a guy is a little lean on the jetting and has adjusted the accel pump out quite a bit, he won't get that indication of it falling on it's face to tell him he is too lean. It falsely fixes it. If he needs 4 1/2 turns out on the accel pump to fix a stumble them he isn't getting enough fuel to begin with.

So if you shut off the accel pump, ride and get it running good with very little stumble under initial acceleration, and then adjust the accel pump out to cure that, you'll be right on every time.

The air/fuel always needs adjusted with any changes to the carb or outside air temp. I knew that. WRM66 never even mentioned the air/fuel adjustment, he was just asking about the tie between the accel pump and jetting.:2thumbs:

 

[T.Byrd]

Im with you bdmridgeback I think he is still a little lean.

 

[WRM66]

ok, guys, went and got me .032 & .033 intermediate jets today at lunch. i also picked up an .080 main jet as well. read up a little from the manual link Ray gave me, but I still have a question.....Should i go up on the main jet as well since I'm running straight exhaust (unbaffled) ,and, according to the post by lee above I am probably running lean. It seems to pull hard on the big end now, but I guess I will have to go run it out and check the plugs to see how they look B4 I mess with the main jet.

 

[Coolbreeze]

EVERYBODIES A BIG DOG MECHANIC!!!!!!!!!!!!!!!!!!!!!!
Go to the S&S web site and download the instuctions

 

[WRM66]

And that's going to do what, coolbreeze???? If it was a stock motor with no alterations, the jetting the manual calls for would work just fine, but it ain't a stock motor.....that's why i'm asking the guys on here some advise. Just about everybody on here has done performance upgrades so i'm just trying to feed off of their experience.

 

[Raywood]

And that's going to do what, coolbreeze???? If it was a stock motor with no alterations, the jetting the manual calls for would work just fine, but it ain't a stock motor.....that's why i'm asking the guys on here some advise. Just about everybody on here has done performance upgrades so i'm just trying to feed off of their experience.

WRM, do your jets one at a time. You will spend most of your time in the Intermediate zone so get that done then you can start working on your main.

Have fun

 

[Coolbreeze]

The tuning instuctions are the same no matter what the engine. The results of your tuning will tell you if you need to go up or down. Your either going to run a 31 or a 32 inter.

I'm talking about tuning proceedure not jet size recomendation.

 

[MARV]

dont forget the simple shit.

the first thing to do when adjusting a carb, especially after a build, is to check for intake leaks.


my built motor with the XXX G ran best with 29.5 / 70 jetting

 

[bdmridgeback]

The tuning instuctions are the same no matter what the engine. The results of your tuning will tell you if you need to go up or down. Your either going to run a 31 or a 32 inter.

Why only a 31 or 32?

I have a stock compression 117, .600 cam, XXX carb, Mean Mothers and K&N.

I run a .033/.076 and it runs hard and plugs are perfect.

I may be still a touch lean on the main jet because if I do higher rpm highway running, hard, the exhaust tips are brown and that is when my plugs are a lighter tan. I may bump up one size on the main jet just to see if I get anymore out of it or not. Summertime it will richen up a bit that is why I have been waiting.

Every engine is different.

 

[Coolbreeze]

My Bad, Your in Florida. Elevation diffrents. I see WRM66 is in Texas, he may need bigger inter too.
The tuning proceedure is still the same.

 

[bdmridgeback]

I am at about the same elevation as texas, just a bit wetter over here!!!

 

[WRM66]

OK, I got into the carb yesterday afternoon. What was in there was a .032 intermediate jet and a .076 main jet. As I stated in my opening post, the guy I got it from told me it was jetted 31/78.....nevertheless, after i put in the .033 intermediate, All the adjustments fell into place according to the S&S manual. I'mm about 1 3/4 out on the air/fuel mixture and about 2 1/4 out on the accel pump screw. I went for a ride and the banging out at 2000 rpm is basically gone. It goes like a bat outta hell when you stab it, so i guess it's all good. Still bangs out a little, I guess where it comes off the int. to the main, but NOTHING like it was. I'm satisfied with this for now, but what about the main jet being .076? As i said, it runs great and pulls hards as is, but should i go up to at least an .078 main? I know I need to check my plugs, but it seems to me, I should be running extremely lean on the big end with the .076......Any thoughts or comments on this ?????

 

[barhopper]

You may be on the lean side. Check plugs. If you really want to dial it in, dyno it and do some jetting changes and redyno it. I would probably say the 78 is needed. The bigger the spread between the 2 jets will make that sputter.

 

[WRM66]

so barhopper, if i put in a .078 will I get that sputtering back again bacause of the further spread between the 33/78 instead of the 33/76 like it is now???

 

[Raywood]

OK, I got into the carb yesterday afternoon. What was in there was a .032 intermediate jet and a .076 main jet. As I stated in my opening post, the guy I got it from told me it was jetted 31/78.....nevertheless, after i put in the .033 intermediate, All the adjustments fell into place according to the S&S manual. I'mm about 1 3/4 out on the air/fuel mixture and about 2 1/4 out on the accel pump screw. I went for a ride and the banging out at 2000 rpm is basically gone. It goes like a bat outta hell when you stab it, so i guess it's all good. Still bangs out a little, I guess where it comes off the int. to the main, but NOTHING like it was. I'm satisfied with this for now, but what about the main jet being .076? As i said, it runs great and pulls hards as is, but should i go up to at least an .078 main? I know I need to check my plugs, but it seems to me, I should be running extremely lean on the big end with the .076......Any thoughts or comments on this ?????

WRM, you really need to go have it tested on a dyno. A good tech will put a gas analyser tube up the exhaust pipes and run it and provide you with a printout of the air/fuel ratio through the RPM range. Otherwise you are just guessing and going by seat of the pants. Way to many variables with pipes, air cleaners, top end work and carb adjustments.

I though I had a print out of my last dyno showing the air/fuel line with in the 13-14/1 ratio we use. Someone else has posted them here before so if you search "Dyno" you may see one. Till them you are guessing or pulling your hair out.



Added:

Here are a couple I found on here by searching "dyno"; We are looking at the lower part of the graph that shows air/fuel mixture.
This one is Neils showing he's ok in the upper range but very lean on the lower:

Here is ChopperDaves and you can see the dyno guy has a red line where the curve should follow. This one is close;

Here is Goofytexan and the best one I've seen. See the magic dotted red line?

And Hoats bike showing a bit lean till the very hi rpm: