TheSamba.com :: View topic - I need help on Weber IDA jetting tuning any info guys?

Sun Nov 18, 2007 11:27 pm

hi guys just looking for some help on tuning jetting my IDA's? this is the specs of motor:
2275cc
mini D port heads 42x37 with matched manifolds had 65cc marked on each head
cam is a 120
1.25 rockers
compression is at 8.5.1
the IDA jetting now is:
40 venturis
F-11 emulsion tube
idle air 120
idle fuel 65
main 170
air 200
motor pulls hard and no problems when opened up mid to high RPM
low RPM it sputter like not getting gas or something? no popping or backfires just sputters on low RPM timing is good. no leaks or nothing it idles fine. motor is brand new just trying to work out the small tuning bugs in carbs. what you guys think up down on jetting? am I pretty close or way off on setup? If I had a magic wand I'd use it by now but don't have one right now all I got is this keyboard! lol. this motor is a daily driver. let me know thanks! [-o<

Tue Nov 20, 2007 8:27 am

Carbs 102: Basic Jetting Theory and Procedure - http://www.aircooled.net/gnrlsite/resource/articles/jetting.htm

Sat Dec 01, 2007 9:12 pm

I read that from aircooled.net any other info or tricks? thanks!

Sat Dec 01, 2007 10:14 pm

Do you have the 3rd progression hole? Also, with 40mm vents you should have F2 e-tubes. For a daily driver with those heads and cam I'd use 37mm vents, F7 e-tubes and start over with your jetting.

Sat Dec 01, 2007 10:39 pm

Your too rich on the idle and main jet. It sputters down low because you are over loading it with fuel and it cant burn it all up. Higher rpms clean up because all the fuel is finally getting used. I would try 55 idle and 160 main jets and see what you think. Just to compare somthing for you.... I had a 2387cc drag engine that was 14:1 comp and I was running 55 idle 170 or 175 main depending on weather conditions, and 195-200 air Hope this helps some ..

Sat Dec 01, 2007 10:57 pm

thanks speedyshift74 I'll try the 55 idle and 160 main. should I stay with F-11 E-tubes? or F-2 E-tube? as per clearsurf2001 suggest? no 3rd progression hole. thanks guys!

Sun Dec 02, 2007 9:30 am

The F-11 tubes should work out ok for now to at least get the fuel right. Just don't go too big of a jet change all at once . You are close to what you want already. I have friends that think just because the engine misses a little its out of fuel... Thats not always the case. I bet you find things to improve with a smaller jet

Sun Dec 02, 2007 11:38 am

speedyshift74 thanks for the advice! yeah my first thought was not enough fuel at low RPM because of the slight sputter? but when I open it up the sputter went away? and I figure my jets was big already 65 idle 170 main and thought if I went down it would sputter more because it might be to lean? but actually it was getting to much fuel "you say" at low RPM? that caused the slight sputter? I'll go down and see if it clears up thanks!

Sun Dec 02, 2007 11:56 pm

clearsurf2001 I PM'd you. let me know thanks!

Mon Dec 03, 2007 3:39 pm

If you have only 2 progression holes I wouldn't go down on the idles. I found I always needed to go up on the idles when I was sputtering at low rpms. I agree with speedy and think you're too rich on the mains. Go down to a 160 or 165.

Also make sure that your sync is dead on and that your linkage is set up correctly with the geometry.

I know how you feel, just finished mine (I think).

good luck

Mon Dec 03, 2007 6:31 pm

57 rag thanks! you live in hawaii? I see the hawaii safety check on your pics.

Mon Dec 03, 2007 10:37 pm

Yeah, I'm out here. If you live out here or a climate close too it, even more so the 55's aint gonna work. Our air here is thicker than shit. I have yet so meet anyone out here using 55 idles, I'm sure there are but I don't know of any. I got the third progression and can't even get slose with them. Come to think of it I'm the only guy I know (like I said...I know) that is even running F-11s. All the shops here tell me only the Harley guys run F-11s in the IDAs. Who knows.

Mon Dec 03, 2007 11:55 pm

57 rag yup me to running f-11's my friend running F-16's thats what he running in his 48's. the air is thick especially with the volcano vog!

Thu Dec 06, 2007 12:07 pm

speedyshift74 I tried the set up you suggested 55 idle 160 mains it ran more worse popping carbs stumble backfires. I sync the carbs and A/F mixture when I changed jets then I tried 60 idle 165 mains got better but stumbles still? then went 60 idle 170 main got better. then I went 65 idle 165 main still same thing? then went back original what I had 65 idle 170 main way better than all other I tried but still has that slight sputter? I notice if I went bigger and bigger it cleared up? go bigger? to rich?

Thu Dec 06, 2007 1:55 pm

you can't quote an idle fuel you are using without also the idle air. On most weber carbs, the idle air is FIXED, but it's changable on the IDA.

I can give you a jetting combo where the 55 idle fuel is too rich, and another where a 70 idle fuel is too lean, DEPENDING ON THE IDLE AIR JET.

Without knowing your idle air you (and others) are wasting their time. Start with a 120 idle air and 60 idle fuel. I'd also try a 100 or 110 idle air and smaller idle fuel.

If you have 3 progression holes you'll need a smaller idle fuel than if you only have 2 progression holes.

and without a wideband to guide you it will be "not easy". In fact you'll NEVER get a perfect tune by "seat of the pants" tuning, you need a wideband for it. If you just want it to drive smooth, just jet it fat and enjoy the 15-20mpg. A perfect tune will get you 30+ MPG, but you need a wideband and a few hours of tuning.

Hopefully you'll have learned more in the past 45 seconds of reading this than the last several hours of "carb tuning".

John
Aircooled.Net Inc.

Fri Dec 07, 2007 12:49 am

john I tried the 120 idle air and 60 idle fuel ran like crap then went 65 idle cleaned up more.I used the breakdown on your website.
CARBS 102: 'basic jetting theory and procedure" it got me close and I THANK YOU FOR THAT! so I'm in the ball park right now where I'm at as far as my set up goes I'm at third base trying to get home and remove that slight sputter! I know now days is technology wideband this wideband that perfect this perfect that. not everybody can dish out $400-$500 to get the tuning perfect. back in the days never had wideband you just had to try this try that adjust this adjust that trial and error thats what. sorry I can't afford technology.

Fri Dec 07, 2007 12:55 am

gumby wrote: ... not everybody can dish out $400-$500 to get the tuning perfect. back in the days never had wideband you just had to try this try that adjust this adjust that trial and error thats what. sorry I can't afford technology.

AC.net rents them for $75, check in the pricing options when you're in his site. If you're really keeping it the $ is nothing compared to the outcome.

Fri Dec 07, 2007 1:13 am

nope never knew! $75.00 what is that a day? or like renting a DVD pay one time and return when you want? If it's 75 clams a day no way. I'll just stick with trial and error and learn the hard way. not going be perfect but close.

Fri Dec 07, 2007 1:23 am

thanks!

Fri Dec 07, 2007 2:06 am

Speedy wrote: AC.net rents them for $75, check in the pricing options when you're in his site.

$75 21 days from date of shipment, Tool Core Charge is $500. thats $575 on credit card not include S/H and insurance both ways. what if it breaks or something. I'll just stick with trial and error not going be perfect but close. thanks speedy.