Weber 44IDF Jetting

[SpyderMike]

I have a 2165 with 44s and I am working through the process of jetting and setting them up right. I am currently at 57 Idles, 160 Mains and 200 Aircorrections with F11 tubes.

Starts and idles fine
Run up throught he idle jets seems fine
Decelerate below 2500 rpm and it is fine
2500 rpm I get surging
Run through 2500 and it smooths out and feels strong
Decelerate on the mains and I get a slight popping
Seems to run out orf steam at higher than 4000 rpm.

I am almost there I think...

Suggestions?

Thanks in advance,

Mike

[yetibone]

Try 1.65mm mains, and 1.80mm air correctors. Sounds like your engine is lean. What size venturis are your 44's equipped with?
...also, how far out are the mixture screws? If they are out more than two or three complete turns, you could go up to say,..60mm idle jets and get some enrichment there.


Yetibone

[SpyderMike]

Thanks for the reply. I worked on it this weekend and it seems that it is a surge when just cracking the throttle on the idles or mains.

Block progression holes in one barrel?

It accelerates fine and idles fine. It is just that when I barely open the throttle under load it surges. It won't do it in my garage...just while driving. Seems lean on one cylinder under laod at cracked throttle.

I have been trying to read up on this, but I find much conflicting information.

The air volume screws are 3 out about 1/4 turn and one closed. The mixture screws are 1/4 to 1/2 turn. The vents are 36mm.

Any clues out there?

MIke

[yetibone]

It's a real trial-and-error prosess when setting up carbs to suit an application. We are running Dellorto DHLA 40s on Hummbug. I got 'em off Ebay for a smokin' deal though. It took me about two weeks to get the mixture right thru adjusting float levels, reaming the mains, and getting smaller idle jets, and smaller emulsion tubes.

I've got a Triumph TR6 that I installed 3 Dellorto DHLA 40s on
(got them from the same fellow on Ebay) I went up in size on the idle jets in .05mm incriments to fix the same situation that you are experiencing. Once I got to .65mm, I found stoichioimetric.

Try to find a tool seller who can provide you with a good set of jet reamers, and guages to measure them with. I got mine from CB Performance. They are far cheaper than buying jets in the long run.

If you have one cylinder that is leaner than the rest, get the engine to operating temp, remove the air cleaners, start the engine, and set three fingers together on one of the velocity stacks. Does the idle go up, or down? If the idle speed drops, then that cylinder's mixture is OK. Try another one. If you find one
cylinder that will make the idle speed rise by blocking the air going into the velocity stack, then that cylinder is lean.

Like you said, possibly a blocked progerssion port.

Yetibone

[SpyderMike]

Yetibone,

you can call me the "grim reamer". got the set from CB and that is what I have been doing all this time. still not there yet. haven't got a clue on which way to go now for fear of f-ing up what got me here. I read all kind of conflicting advise.

gotta try somehting though...i'm too young for dentures and the surging is loosening my teeth.

[yetibone]

Hey Mike,
I know you are running Webers, but if you can find a copy of the Dellorto Superformance Handbook it may be helpful to troubleshoot your drivability problem. I think it was written by Bob Tomlinson, at CB Performance, and has a number of pages devoted to carburetor diagnostics on larger two barrels like DRLA, and DHLA. Since DRLA's and Weber IDF's are alike in function, although not in design, it may have some ideas that help.

Yetibone

[Dougy Dee]

Depending on your cam and compression, you may be running RICH.

Assuming 36 venturisand 200 airs, drop down to a 145 or 150 main and 55 idle. Adjust the pump jet so you get equal shots out of both carbs.
If you are running an A/F gauge ignore it at cruising speed. It should show wicked lean and come back to stoich when feathering the throttle.

My 2110 is running a 140 main and balance of jetting as above.

Good Luck

[factman]

one problem that i ran into is that if the carbs aren't exactly sinqed then the throttle plates pass over the progression ports are different times and that was why my engine was surging just under load and not any other time. just a suggestion.