Topic: Weber carb set-up

[BPellerine]

Okay one more question. I read on here about a ball to be careful with....I have found none but there are a couple of 1/2 inch metal pieces, rounded at the ends, that may be doing the same thing? Is that common?
you may have to turn the carb upside down to get the balls out,they are very small so be careful ,in the books they are called the stuffing balls.bill

There are small steel balls under those brass pieces; the brass parts act as weights to prevent the accelerator pump from squirting with small or slow throttle movements. There is also a small plastic ball inside the spill valve, but it is locked in place.
Some aux have a 1,2,3,or 4, but that isn't the size. Look at Greggo's thread; I posted pics of the location of the size.
I run foam Uni filters over air horns. The air horns are required to hold the whole throat assembly in place.

[BPellerine]

scott I have 3.5 chokes as well,checked as I thought they were 4.5,29mm chokes.bill

[Swoop]

There are small steel balls under those brass pieces; the brass parts act as weights to prevent the accelerator pump from squirting with small or slow throttle movements. There is also a small plastic ball inside the spill valve, but it is locked in place.
Some aux have a 1,2,3,or 4, but that isn't the size. Look at Greggo's thread; I posted pics of the location of the size.
I run foam Uni filters over air horns. The air horns are required to hold the whole throat assembly in place.

Okay...sorry I don't understand about the steel balls...under what brass pieces?
I have what looks like logs that are free to move in one of the channels under a brass screw.

Steve

[Swoop]

Okay....so I found the steel balls in my ultrasonic.
The auxiliaries he was running were 4.5
The spare set are 3.5

For reference you can find the aux numbers adjacent to the holding spring.

Steve

[scottly]

Glad you found them.

[Swoop]

A couple of questions regarding air horns.
1- Anybody have a spare set?
2- How do I know if I need slide in or bolt on type?
3- The Czech guy on eBay sells some bolt on that are over 2"in length, will that fit our bike? What length do you run?
4- Has anybody bought his rebuild kits or other parts? What is the quality like?

Thanks

Steve

[scottly]

2. The aux determine if you need slide in or bolt on horns. If your aux have a step in the OD, you need the slide in style. If you insert the aux into the carb, there will be a small gap between the OD of the aux and the ID of the carb. This gap is filled by the air-horn. Pierce has 1 1/2" slide in horns for $36.85 each. I think mine are 1"? I'll snap a pic later today.

[scottly]

My horns only stick out from the face of the carb body about 3/4". The second pic shows how the horn slides over the aux. There were also sleeves with no bell, used with air-boxes.

[Swoop]

Thanks Scottly,
My aux's are like yours....and it looks like, from your frame pic, a slightly longer horn would not be a problem.

Steve

[scottly]

Steve, Carbs Unlimited has aluminum stacks (air-horns) in 16mm and 26mm lengths for $27.95:
http://www.carburetion.com/sitesearch.aspx?category=DCOEstack&Title=Stacks%20for%20Weber%20DCOE%20Carburetors

[scottly]

I made the cardinal mistake of changing two things at the same time today: I went from 120 mains to 110 mains due to the over-rich A/F in the 5200-6600 RPM range, and from 185 airs to 175 to due to the lean A/F at higher RPMs. Seems the air jet has more effect in the mid-range than the high end as the literature suggests? I'll retest with the 110 mains and the old 185 airs.
 

[BPellerine]

you are getting down in the main jet size,maybe the smaller sizes are better,I have always thought that my carbs were jetted for the smaller bore engines,ie 736,836,but everyone seemed to be at 125,for 836.bill

[scottly]

I swapped the 175 airs back to 185s and found that it leaned the A/F across the 5200-7500 RPM range. With Frank's soft boots I found I could loosen the spigot clamps and tilt the carbs down enough to remove the main jet/emulsion tube assembly with the carbs mounted in the Seeley frame, with the boots still mostly on the spigots. Much easier than completely removing and remounting them. The whole job took less than 30 minutes. I've also noted some irregularities in the A/F, such as in this latest run from 4250-4750 RPM, which should be reflected in the HP/torque curve, but isn't. Decided it was time to inspect/clean the sensor again... 

[754]

I think when I cut the boots, I wanted 1/4 between the spigots and manifold.. Plenty of wiggle room.
 They look like they may stay soft a long time ...
 The RC manifolds look like you may have to lower the carbs, to change the jets.
 On the splayed manifolds they seem to clear frame a bit better.

[Jerry Rxman Griffin aka MuthaF'er]

#$%* Scott, you got some good numbers! What are you hiding besides the Webers in plain sight?

[BPellerine]

ok if I get this right the larger air corr is leaning out the mixture on the top end,I have 200 airs and 115 so on the ballpark?bill

[scottly]

 They look like they may stay soft a long time ...
 

I think they will stay soft forever.

ok if I get this right the larger air corr is leaning out the mixture on the top end,I have 200 airs and 115 so on the ballpark?bill

The air jet is effective throughout the main jet range, at least from what I've gathered. Two sizes down on the air had more enriching than two sizes down on the main leaned the mixture. 4.5 aux are richer than 3.5. Larger chokes are leaner, Especially above 7000 RPM, as there is insufficient vacuum to lift the stuffing weight and allow the accelerator jets to perform high speed enrichment. In the case of the last dyno test, this starts to happen at 7500, but the motor was dangerously lean at 7250, and the spark plugs showed it. I'm going back to 30mm chokes; I now know how to make the 32's work with 836cc's, but I doubt it's worth the effort.

#$%* Scott, you got some good numbers! What are you hiding besides the Webers in plain sight?

Jerry, it's a TRW piston 836, with a mystery reground cam; near as I can measure, the valve lift is .310" ex, .315" in. The head is a stock, un-ported K1, and the last time the top end was apart was in June of 1979.

[mwasson]

Here is what I ordered to put in my Webers and then will take it to a dyno in Germany and fine tune it as necessary-

Engine- 836cc, ported head, Webcam 63a.

Choke Weber 40 DCOE: 30mm   (current 28mm)
Weber auxillary venturi 4.5 40 DCOE   
Emulsion tube: Weber DCOE/IDF F16   and F11
Main jet: Weber DCOE/IDF 120   
Idle jet Weber DCOE: 45F8   
Pump jet: Weber DCOE 35   
Pump spill 55 Weber DCOE   
Needle valve: Weber DCOE 200   
Air jet Weber DCOE/IDF/IDA: 170   

Hopefully this takes out the sputtering from 4000-5200ish.

[scottly]

MW, what jets are you currently running? Chances are you are already running either f11 or f16 emulsion tubes. A pair of 150 needle valves can support up to 120 HP.
People, please don't spend money on tuning parts until I can finish my dyno testing. 

[BPellerine]

we should thank you for what you are doing!thanks billp

[mwasson]

I currently have F11s, will try the F16s on the Dyno in Germany. If it is too lean, will go back to the F11s.

What is a good starting point with the needle valves, 150?

Also, what effect do you think it will have going from 28mm venturi to 30mm?

Thanks.

[scottly]

The needle valve size is a non-issue; whatever your carbs came with is fine.
I have only F11s on hand, so I can't compare them to F16s. The main jet and air jet are of far greater importance than the emulsion tubes. Increasing the choke size with no other changes will lean the mixture, as shown by the chart in reply #607. I suspect your issues from 4000-5200 RPM are due to an extremely rich condition. How big are your main jets and your air jets?

[mwasson]

I will check with my Dad and see. He has the dyno print outs as well. I will get all the information from my Dad. I am currently in Afghanistan, the bike is on a ship to Germany and he is in Oregon...

I have found a tuning shop in Germany with a dyno and will take it there next year when I get some vacation time. In the meantime, I am ordering new Webers so I can get them set up as close to possible here in Afghanistan, and then slap them on the day I get home and get it to the dyno. Time is money for me, as I only get five weeks a year at home and getting a set of carbs set up close here is the best option for me.

[scottly]

Time is money for me

I've got the time, but not the money. Send me some money and I'll not only save you some time, but also some money on parts that will never get used.

I went back to 30mm chokes, with the same 3.5 aux and 110 main as the last test, but with a 200 air, as I knew the smaller chokes would be richer. After a couple of warm-up runs to make sure the pistons weren't going to go China Syndrome at 7250 RPM, I let it rev a bit more than before.
I also figured out how to use the vertical cursor option to show the readings at a particular RPM. The A/F readings were still a bit wonky, but after cleaning the sensor again (by carefully heating it with a propane torch to drive off the fuel residue), it seemed to operate properly for the next test. As most folks seem to have 4.5 aux, I ran another test with them installed in place of the 3.5s.
The last graph compares the tuning I've run for 36 years, that my "butt dyno" thought was good, compared with the 110 mains and 200 airs.

[mwasson]

#$%* Scott, you got some good numbers! What are you hiding besides the Webers in plain sight?

Mine put out 68 RWHP which I was thinking was not that great, but looks like it is not bad. Will see how she does once I get the sputtering sorted out from 4000-5200, as the power dropped significantly and then shot right back up to 68 at about 8500ish. I will get the dyno sheet scanned and emailed to me and post it.