Author Topic: Weber carb set-up (Read 151773 times)

mwasson · « **Reply #725 on:** December 16, 2015, 07:17:44 AM »

Tintop-

Exactly. When you get into the nitty gritty on these Webers for that "perfect tune" that they are capable of, the
I am trying to wrap my head around this last part of the puzzle. This Weber tuning is a real science!

I have zeroed in on the idle jet, main jet, A/C jet, emulsion tube and aux. venturi and choke size from Scottly's great research on the dyno, as well as the tuning DVDs and manuals I bought from Pierce Manifolds.

The most difficult thing I see now is the size of the Accel. pump jet, the duration of the shot of fuel, and the bleed back into the bowl to get the perfect tune.

BPellerine · « **Reply #726 on:** December 16, 2015, 11:59:29 AM »

if you read back,scott is talking about his pilot or idle jets,from what I understand you are still on the idles when just cruising at 60mph,he had the same symptom before and cured it by upping the idles from 40 to 45,and now with the revised settings he is going to 50 idles.bill

scottly · « **Reply #727 on:** December 16, 2015, 06:19:31 PM »

Yes, Bill got it right, I was talking about upping the idle jets to 50s. The other clue is the setting of the idle screws, which are backed out slightly past the upper limit for the old carbs I have, a bit over 1 turn out. I'm using the original 35 pump jets and 55 spill jets. If the choke size is matched to the motor size: 28mm for 736cc, 30mm for 836cc, and 32mm for 950-1000cc, you shouldn't have to do much, if any, change in the accelerator pump system.

mwasson · « **Reply #728 on:** December 17, 2015, 01:54:16 AM »

Ok. I got it. Got confused with the terminology.

So, are we looking at a set of F8 or F9s at .50?

Thanks guys,

Mark

scottly · « **Reply #729 on:** December 18, 2015, 06:59:12 PM »

I'm thinking of going to 50F8, as the 45F9 were only slightly lean. Unlike the emulsion tubes, there is a code for the idle F#s, and an F8 is one step leaner that an F9. It's more like the relationship between the air jet and the main jet.

mwasson · « **Reply #730 on:** December 19, 2015, 12:56:51 AM »

Sounds good. I will get a set of 50F8s and try those as well.
Scottley,

On another note, I am thinking of putting air filters on my bike.

I have came down to two choices that would fit between the frame and the carbs.

The Lynx Ram-Flo and a KN 56-1270 assembly with the E3321 filter. It is only 1 3/4" thick so it should fit in place of the velocity stacks.

Now, with either of these filters, the velocity stacks won't work, even the short 16mm stacks.

I am wondering how the performance will be affected if you take off the stacks entirely and run just the Ram Flo or K&N. I have searched for some stubby stacks to try to fit inside but cannot find any.

I understand the shorter stacks produce power at a higher RPM and the longer in mid and low range, depending on the overall distance from the stack opening to the intake valve.

Since these are the only two filters that could possibly fit in the space, which would you recommend, or should I just run screens (like I have on now) and stay out of dusty areas.

I have a set of Ram Flo filters now, but looking at them, there is hardly any room for a stack unless it was super short. I hate to sacrifice mid range power, but also do not want to wear the motor out prematurely.

I guess a guy could dyno both setups and see what happens. Do you have any research/information on this subject?

RAZZ · « **Reply #731 on:** December 19, 2015, 02:33:40 AM »

What about thiese:http://ramair-filters.co.uk/cs-carb-socks

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scottly · « **Reply #732 on:** December 19, 2015, 07:14:01 PM »

Mark, the stacks do more than provide a rounded entry to the carbs; they also lock the throat assembly firmly in place, when properly installed with the tabs under the nuts on the studs. I believe your carbs are missing those locking tabs?
I did do back-to-back baseline runs at the beginning with open stacks and UNI foam filters over the stacks, and found no major difference, but I didn't do a test with the filters after the final jetting runs.
The filters I'm currently using are 2" ID x 6" long, with about 2" cut off the length.

mwasson · « **Reply #733 on:** December 20, 2015, 08:18:09 AM »

Quote from: scottly on December 19, 2015, 07:14:01 PM

Mark, the stacks do more than provide a rounded entry to the carbs; they also lock the throat assembly firmly in place, when properly installed with the tabs under the nuts on the studs. I believe your carbs are missing those locking tabs?
I did do back-to-back baseline runs at the beginning with open stacks and UNI foam filters over the stacks, and found no major difference, but I didn't do a test with the filters after the final jetting runs.
The filters I'm currently using are 2" ID x 6" long, with about 2" cut off the length.

Scottly,

The Lynx Ramflo filters do have a tab that bends in for that purpose.

There is no way to fit in the stacks with those filters.

They show that they are installed without the stacks in the instructions.

I just wonder how it wil adversely affect performance if I use the ramflo system.

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Tintop · « **Reply #734 on:** December 20, 2015, 10:02:11 AM »

You can use stacks with the Ram-flow type filters, and you can use either style of stack (bolt-on with flange, or slip in with tab keepers), with the appropriate choke. Biggest problem with the Ram-flows is their size, as they are designed for use on cars with more space.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #735 on:** December 20, 2015, 05:25:52 PM »

OK guys, nitty gritty time. Need to mount some carbs SOON. Both sets of intake manifolds are hard as a rock. Can't use them with this build. Early head/spigots. Early intakes too, to fit the Webers?

Best deal going is....... ??

Probably use stockers at least for break in. The Webers need to have a little welding/brazing work due to shipping damage to the thingy that the cable attaches too.

scottly · « **Reply #736 on:** December 20, 2015, 05:58:34 PM »

Quote from: Tintop on December 20, 2015, 10:02:11 AM

you can use either style of stack (bolt-on with flange, or slip in with tab keepers), with the appropriate choke.

With the appropriate Auxiliary choke.

scottly · « **Reply #737 on:** December 20, 2015, 06:01:53 PM »

Quote from: Jerry Rxman Griffin aka MuthaF'er on December 20, 2015, 05:25:52 PM

OK guys, nitty gritty time. Need to mount some carbs SOON. Both sets of intake manifolds are hard as a rock. Can't use them with this build. Early head/spigots. Early intakes too, to fit the Webers?

Best deal going is....... ??

Probably use stockers at least for break in. The Webers need to have a little welding/brazing work due to shipping damage to the thingy that the cable attaches too.

Jerry, you might try the wintergreen oil trick to soften the boots?
Post a pic of the broken "thingy".

754 · « **Reply #738 on:** December 20, 2015, 06:59:36 PM »

Have you been playing with the air correction jets, or am I using the wrong name perhaps?
One thing I am curious about, and would like to clear up. Back in the day they often wrote that the float jet was modded for gravity feed applications ..ie motorcycles. Does anyone know if they were just drilled out or came in several sizes. ?

Tintop · « **Reply #739 on:** December 20, 2015, 07:58:46 PM »

Quote from: 754 on December 20, 2015, 06:59:36 PM

Have you been playing with the air correction jets, or am I using the wrong name perhaps?
One thing I am curious about, and would like to clear up. Back in the day they often wrote that the float jet was modded for gravity feed applications ..ie motorcycles. Does anyone know if they were just drilled out or came in several sizes. ?

The float needle is/were available in different sizes (and tip composition). Not sure how it would have been modified though.

scottly · « **Reply #740 on:** December 20, 2015, 08:11:48 PM »

I played with a LOT with air jets!

The float jets come in sizes from 1.5 up to 3.0, but a single 1.5 is capable of supplying 60 HP, with a pump pressure of only 2 PSI. I think mine are 1.75? No starvation issues with gravity feed detected.

754 · « **Reply #741 on:** January 16, 2016, 11:17:57 AM »

This is what everyone needs..

RAZZ · « **Reply #742 on:** January 16, 2016, 11:34:02 AM »

Look what the mailman came with today, looking forward to open Them up ane see what i Got

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Jerry Rxman Griffin aka MuthaF'er · « **Reply #743 on:** January 16, 2016, 11:57:09 AM »

Quote from: 754 on January 16, 2016, 11:17:57 AM

This is what everyone needs..

Doesn't look like you need them sitting there all packaged up like that

Need my address?

Medyo Bastos · « **Reply #744 on:** January 16, 2016, 01:17:38 PM »

Quote from: Jerry Rxman Griffin aka MuthaF'er on January 16, 2016, 11:57:09 AM

Quote from: 754 on January 16, 2016, 11:17:57 AM
This is what everyone needs..

Doesn't look like you need them sitting there all packaged up like that Need my address?

i think my address would be more suitable!

...Save a tree, eat a beaver...

scottly · « **Reply #745 on:** January 16, 2016, 08:11:46 PM »

Quote from: 754 on January 16, 2016, 11:17:57 AM

This is what everyone needs..

I guess now I need to post a pic of my collection of Weber bits? Hmm, going to have to clean off some workbench space first.

Greggo · « **Reply #746 on:** February 13, 2016, 08:52:37 AM »

Question regarding fitment with the RC manifold: Do the stock air box mounting tabs need to be shaved to fit these? Mounting to a K4.

BPellerine · « **Reply #747 on:** February 13, 2016, 02:33:51 PM »

I am not using rc manifold,but I had to bend my tabs upward to fit mine,do that before cutting them off if needed.billp

Tintop · « **Reply #748 on:** February 19, 2016, 04:18:17 AM »

You do nee to have some kind of support for the carbs. Either from above, or below. Otherwise the weight will cause them to sag on the rubber boots and throw your float adjustment out of wack.

It should ideally be a vibration free mount so the inherent engine vibration does not churn up the gas in the float blow. my .02

Greggo · « **Reply #749 on:** February 26, 2016, 04:23:06 PM »

Quote from: Tintop on February 19, 2016, 04:18:17 AM

You do nee to have some kind of support for the carbs. Either from above, or below. Otherwise the weight will cause them to sag on the rubber boots and throw your float adjustment out of wack. It should ideally be a vibration free mount so the inherent engine vibration does not churn up the gas in the float blow. my .02

The RC manifold I have has a threaded hole for a support bracket. I'll rig something to the frame from that center mount to a spare coil-to-frame mount I've got.

Do you guys run stock petcocks?

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Author Topic: Weber carb set-up (Read 151773 times)