Topic: Weber carb set-up

[jonnycakes]

I'm so close...put in the 28mm 110 main 150 air (smallest I got) and 40f9.  Starts right up and idles when warm. Will pull if I roll slowly the throttle (no squirter) and when whacked hard(squirters). Still feel like it's going rich when at speed I close and then reopen the throttle. It takes a sec to clear its throat.

[BPellerine]

did you try a plug chop?when it does clear how is the response?

[jonnycakes]

YUP...looks good in the idles, looked good top end. Went to the 28mm chokes to make sure I was bring in the mains early.

[scottly]

Where are your idle mix screws set with the 40s?

[jonnycakes]

1 full turn

[scottly]

Everything about your set-up is lean, except for the 150 airs, which only kick in at higher RPMs. When cruising at a steady 65 MPH, I'm still mostly on the pilot jets. The early carbs like ours with the wider angle mixture screws should be 1/2 +/- turns out with the proper jets. Without changing anything else, go back to the 45s and report back.

[jonnycakes]

Great idea, I'll do it and report back. Thanks for all the help

[jonnycakes]

I went with the 30mm 120 main 170 air and 40f9 idle.  Starts right up and idles when warm. Run great but a little stumble off idle when cold and warm, Maybe back to the 45s idles?

[BPellerine]

must be diff with the auto,only tried two sets of webers and both had quick throttle response on the lower end,my own better than the other set cause they had diff jetting.bill

[Tintop]

I went with the 30mm 120 main 170 air and 40f9 idle.  Starts right up and idles when warm. Run great but a little stumble off idle when cold and warm, Maybe back to the 45s idles?

Could be your accel pump jet size, or the bleed back size. 

[BPellerine]

one thing I did notice when I was getting mine ready,I had the top off the carb and was pumping cleaner through it,this showed bubbles coming out of the pump jet orings and the screw that holds the stuffing ball,I was losing pressure in these places to the pump,doing this showed me a little about how the fuel flows as well.bill,it cured a small hesitation I had

[scottly]

Maybe back to the 45s idles?

The 45s worked best for me.

[jonnycakes]

After much trial and error:

30mm chokes (32mm chokes too big, 28mm chokes too small)
4.5 Aux Venturi
F16  Emulsion Tube
120 main (125 main way too big)
45F8 Idle jet (40F9 Idle jet just a bit small)
35 pump jet
Pump Spill  55 (what is stamped)
.200 needle valve
170 AIR CORRECTOR JET

running 120mph on the highway, and a touch of wheel spin when i wack the throttle at low speed.

DONE

[scottly]

I had my bike on the dyno on Monday, and found it to be way too rich above 4500rpm with 125 mains. Before I could change anything, the drum bearings on the dyno started making ugly noises. New bearings are on the way. I was going to try 32mm chokes first, because I think I can change them without removing the carbs, unlike the mains with the Seeley frame. I do have a set of 120 mains, so your news is encouraging.

[johno]

Johnny gogo,
Your finished carb specs are almost identical to what I used to run on a few of my 750 honda's with cam, ports and rc exhaust and 30choked webbers.....32 was to big and 28 too small , jets stuff all the same as you ended up with, run nice.
 

[BPellerine]

great news ,I have 29mm chokes 115 mains and 200 airs,so I am not that far from you,everything else the same,maybe need small change with bigger motor when that happens.billp

[jonnycakes]

Now to ride.....

[Greggo]

great news ,I have 29mm chokes 115 mains and 200 airs,so I am not that far from you,everything else the same,maybe need small change with bigger motor when that happens.billp

Bill,

Thanks for the previous info.  I'm going to set the ones up from Bill Benton on my stock (for now) K4 motor.  Bill pulled them from a drag bike..so I guess my question is: which pieces will I likely need to swap to get it to run on a smaller motor for the street?  I have master rebuild kits coming in next week, then I'll disassemble one at a time and dip in some magic sauce at the shop.

[scottly]

The chokes are the main thing you made need to change, depending on the size of the motor. What parts are included in the rebuild kits? Don't soak the accelerator pump spill jets in the magic sauce, as they have a plastic ball inside, and the magic stuff may damage them.

[BPellerine]

great news ,I have 29mm chokes 115 mains and 200 airs,so I am not that far from you,everything else the same,maybe need small change with bigger motor when that happens.billp

Bill,
geggo,when you get your carbs record all the diff jet values,and your choke and aux venturis,then compare to what you see on here ,you will get a ballpark setting and then you may have to tune some.the stock motor is about as small as these carbs run on ,just my opinion,so you have to be fairly close,ie not too big.I have only been running mine for a couple of years,scottly much longer.bill

Thanks for the previous info.  I'm going to set the ones up from Bill Benton on my stock (for now) K4 motor.  Bill pulled them from a drag bike..so I guess my question is: which pieces will I likely need to swap to get it to run on a smaller motor for the street?  I have master rebuild kits coming in next week, then I'll disassemble one at a time and dip in some magic sauce at the shop.

[BPellerine]

I do not use strong cleaners,wd40,brake cleaner,small brushes,and air.these carbs are made out of a metal called mazac very crappy metal that will crack easy.there is finish on them that chips and you end up with a dark spot that you can clean but come back quick,I just live with it.I have seen these carbs painted,and even chromed but I could not imagine what it would take to do that.they have some detailed parts and passages that I would not blast.you can buy a lot of stainless for them.bill

[Bill/BentON Racing]

Gregg, I found that stock ignition wouldn't be enough at slow speeds, idle etc. Went to a RC distributor setup, and no more problems.  Stock 736cc 750 model, 30mm chokes, Bill

[BPellerine]

Gregg, I found that stock ignition wouldn't be enough at slow speeds, idle etc. Went to a RC distributor setup, and no more problems.  Stock 736cc 750 model, 30mm chokes, Bill

been holdin back bill?haha when I got mine I searched for someone that had run them on 736,most 836 and up.billp

[Greggo]

The chokes are the main thing you made need to change, depending on the size of the motor. What parts are included in the rebuild kits? Don't soak the accelerator pump spill jets in the magic sauce, as they have a plastic ball inside, and the magic stuff may damage them.

I'm glad I asked...I'll just clean them carefully by hand.  Some rusty spots I spritzed with Kroil.  Haven't seen the rebuild kits yet..next week. 

Gregg, I found that stock ignition wouldn't be enough at slow speeds, idle etc. Went to a RC distributor setup, and no more problems.  Stock 736cc 750 model, 30mm chokes, Bill

Was going to use a Dyna III on this bike...good 'nuff?

[Retro Rocket]

The chokes are the main thing you made need to change, depending on the size of the motor. What parts are included in the rebuild kits? Don't soak the accelerator pump spill jets in the magic sauce, as they have a plastic ball inside, and the magic stuff may damage them.

Was going to use a Dyna III on this bike...good 'nuff?

Yes...