Author Topic: Weber carb set-up (Read 151805 times)

Swoop · « **Reply #650 on:** October 20, 2015, 03:12:54 AM »

Quote from: scottly on October 17, 2015, 08:36:02 PM

Quote from: mwasson on October 16, 2015, 09:56:34 PM
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.

Hey Scottly....so does this complete your journey? Looks pretty good.
I, for one, appreciate the legwork that you have been doing. It will be helpful to many on the forum...now and in the future.

Thanks

Steve

scottly · « **Reply #651 on:** October 20, 2015, 07:31:46 PM »

Hey Steve, no, I'm not done yet.

It's still rich from about 4300 to 6300 RPM, depending on the aux, and lean above about 6900 RPM, regardless of the aux. It appears that the combination of the main jet and the pump jet supplies the fuel at higher RPMs, and if the main jet is reduced to lean the mixture in the mid-range, the pump jet needs to be increased to make up the difference at the high end. I've got a set of pump jets that have already been drilled to about .458 to compare to the original .35; I expect to see the A/F go rich near the same point where it went lean before.

Bill/BentON Racing · « **Reply #652 on:** October 21, 2015, 12:08:37 PM »

My 836cc tired it was, only put out 65rwhp. The 915cc a different story! I

, Bill
You should take Scottly up on his offer if possible, he knows dem Weber's !!

Tintop · « **Reply #653 on:** October 21, 2015, 02:36:25 PM »

Quote from: scottly on October 20, 2015, 07:31:46 PM

Hey Steve, no, I'm not done yet. It's still rich from about 4300 to 6300 RPM, depending on the aux, and lean above about 6900 RPM, regardless of the aux. It appears that the combination of the main jet and the pump jet supplies the fuel at higher RPMs, and if the main jet is reduced to lean the mixture in the mid-range, the pump jet needs to be increased to make up the difference at the high end. I've got a set of pump jets that have already been drilled to about .458 to compare to the original .35; I expect to see the A/F go rich near the same point where it went lean before.

That's been my experience. You may find that with the larger pump jet you have to change the bleed valve so you don't go rich off the accel pump action.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #654 on:** October 21, 2015, 04:45:41 PM »

You guys are scaring the #$%* outta me! It will be carb time soon. Maybe go with my original carbs to get the engine squared away then fly Scott in from Mesa @ $85 RT to install and tune Webers!!

BPellerine · « **Reply #655 on:** October 21, 2015, 05:28:13 PM »

hell jerry don't let fear stop you!I agree with stock carbs for startup,but you will find that the webers are not as intimidating as you think.haha bill

Bill/BentON Racing · « **Reply #656 on:** October 21, 2015, 05:49:23 PM »

Jerry ,they'll give you a headache! Send to me for these CR31's.

754 · « **Reply #657 on:** October 21, 2015, 06:40:41 PM »

If they have baseline jetting, it should start up and be rideable.
If you start of with different brass than recommended, then it can be more work.
They are not that mysterious, and there is plenty of help here...

scottly · « **Reply #658 on:** October 21, 2015, 06:50:11 PM »

Don't be skeered, Jerry, by the time you're ready I'll have any headaches sorted out.

If you want me to tune your Webers to a gnat's ass for your motor, you'll have to bring it to Scumboldt (and pay me).

Jerry Rxman Griffin aka MuthaF'er · « **Reply #659 on:** October 21, 2015, 07:38:36 PM »

Scott, I've already burned a month away plus 3 more upcoming weeks. Will that give you enough time?

scottly · « **Reply #660 on:** October 21, 2015, 07:49:00 PM »

I was hoping to have an update today with the larger pump jets, but Mother nature reared her ugly head and sent thunder and lightning, hail, and heavy rain for a short period of time, like almost 1/2" in 15-20 minutes.

scottly · « **Reply #661 on:** October 22, 2015, 08:16:34 PM »

The larger pump jets were only effective above 7300 RPM. The overall increase in both torque and HP in the last test might be attributed to fresh gas vs 2-3 month old gas? I'm going to go to 100 mains and 175 or 185 airs to see if I can get the A/F in the 4500-7300 range more even.

scottly · « **Reply #662 on:** October 24, 2015, 08:08:44 PM »

Did a couple of tests today with 100 mains and 175 and 185 airs. Once again, I'm surprised by how great the influence of the air jet is on the mid range.

BPellerine · « **Reply #663 on:** October 25, 2015, 04:27:13 PM »

had a set here that were supposed to be set up for 836,170 air,105 main,dont know how it was arrived at,but not that far off your findings.bill

scottly · « **Reply #664 on:** October 25, 2015, 07:04:15 PM »

Bill, what size were the chokes and aux on those carbs?
I did a test today with 200 airs, and they had little overall effect compared with 185s??

BPellerine · « **Reply #665 on:** October 26, 2015, 11:13:48 AM »

scott they had 30mm chokes and if I remember 4.5 aux,they belong to bill Benton so you might want to check with him,I had them running on my bike but only to see if they were working ok.billp

scottly · « **Reply #666 on:** October 26, 2015, 06:12:53 PM »

Tested 89 mains today (closest I could get to 90 with available drill bit of .035"). Also went back to the 35 pump jet, as it didn't help much at the top end, and as Brian said, created issues at the bottom end. HP and torque were both up in the mid range; despite being lean, the A/F was still closer to ideal than with 100 mains and the same 185 airs. I'm going to try 175 airs next, and depending on the results, may try smaller airs.

scottly · « **Reply #667 on:** October 29, 2015, 07:28:32 PM »

*Disclaimer* The "100" main jets are actually soldered and drilled with a .040" bit, which measures 1.016mm, and as I've said before, drilled jets are like a box of chocolates; you never know exactly what you're going to get.

scottly · « **Reply #668 on:** October 30, 2015, 07:21:16 PM »

The latest round of tests has been with "105" mains, and "210" airs. (the 175, 185, and 200 airs were Weber sizes, while the "210" was drilled) The large jump in the HP/torque readings for the last two runs are more due to less tire slippage than jetting, as I adjusted the tire pressure just before run 297.
* If you have 30mm chokes, 4.5 auxiliaries, and F11 emulsion tubes, I recommend 105 mains with 210 air correction jets.*

Tintop · « **Reply #669 on:** October 31, 2015, 06:45:17 AM »

What was the filter &/or stack (or non?) set-up scottly?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #670 on:** October 31, 2015, 09:00:18 AM »

71 and climbing. Maybe no more peak but higher mid-range curve available. Keep at it.

scottly · « **Reply #671 on:** October 31, 2015, 11:11:17 AM »

Brian, all tests have been with open 16mm stacks. I would rather err on the rich side, as I'm at 4500' elevation, and the motor is tired and burning some oil, which may be affecting the A/F readings.
Jerry, smaller mains improve the mid-range slightly, but at the expense of the high end; this is as good as it's going to get with 4.5 aux and F11 emulsion tubes. Anyone have a spare set of F16s or be willing to lend me a set to test with?

Tintop · « **Reply #672 on:** October 31, 2015, 01:58:15 PM »

scottly, I've got x2 F16's, and if you wanted to try the other side of the F11's...a pair of F9's. Glad to lone them for continued testing, to add to the set-up data.

On another note, while looking for the e tubes I found an accel spring (#47600.055). It came from Pierce (3+yrs ago?), so they are available in US. Someone was looking for them, can't remember who though.

scottly · « **Reply #673 on:** October 31, 2015, 07:42:40 PM »

Thanks for the offer Brian, but with the high postage cost to ship to/from Canada, and the fact that I need four tubes, I'll have to pass. Worst case I'll buy some from Pierce, but I had hoped to order mains and other jets at the same time after testing F16s.
I did a couple of tests with 3.5 aux; they tend to make the main jet work as if it is smaller than with 4.5s. The one thing that has been constant throughout the testing is the tendency to be rich in the mid-range, and lean at the top-end, with F11s. Any of the most recent jetting combinations are far better than what I started with, gaining 9-10 HP in the mid-range.

754 · « **Reply #674 on:** October 31, 2015, 07:48:31 PM »

Stuff thinner than 20 mm , goes letter post up to around 100g or maybe more..like 4.00 or so
If i can get to my stuff i will look, pretty sure i have F16,s in both..but in my jet box i have. At least two other nu.ber emulsions...
Which do you think is preferred one to use? Not so bad using the others, if you can start off in the ball park.

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Author Topic: Weber carb set-up (Read 151805 times)

Swoop