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Old 04-15-2013, 05:43 AM
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It does the same thing cowl on or off
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Old 04-15-2013, 06:03 AM
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Best fix to most induction pressure/air flow .... has to be the 3W snorkel .
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Old 04-15-2013, 01:11 PM
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Personally, I do not think it is diaphragm pressure related, so no amount of snorkels or similar stuff will improve it. The static ports you have now should do.
Question;??
What is your pop-off pressure? If below 20lbs/in^2 that would explain a lot, together with maybe a high fulcrum lever setting. Beware, lever height can be extremely critical.
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Old 04-15-2013, 02:03 PM
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I will check it when I get the carb off again. Will likely do that later in the week.
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Old 04-16-2013, 04:24 AM
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tim, Pe's point about pop off pressure is very valid
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Old 04-16-2013, 04:45 AM
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I was checking out my 116 today, and had the carb off. (WB27)
Pop-off pressure @ 15lbs, re-seat a mere 10 lbs. That is on the verge of constant leaking.
I stretched the lever spring from 12.5mm to 14.5mm. After that, pop-off was 26lbs, stable re-seat at 16 lbs.
Blowing into the vent hole gave stable carb operation every time.
Keeping the carb at 20lbs pressure, I thumped the carb on the pump cover with clenched fist, My estimate applying about 10G acceleration. (I know from past acceleration experiments, not exactly, so give or take a little). With each thump, carb pressure dropped about 2 lbs, until it stopped doing that at 15 lbs.
Conclusion:
Carb acceleration can take away as much as ~10lbs of pop-off pressure. So if the carb is at 15lbs pop-off, it will very probably start to inject fuel into the engine. The amount injected IMHO is in relation to pop-off values. Dump just a little, or dump the whole plenum chamber content at low pop-off.
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Old 04-16-2013, 07:46 AM
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Thanks, I will certainly check that ASAP.

Danke u wel
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Old 04-16-2013, 08:49 AM
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Very good info PE.
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Old 04-16-2013, 09:15 AM
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Quote:
Originally Posted by JoeAirPort View Post
Very good info PE.
+1 thanks Pe!
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Old 04-16-2013, 10:36 AM
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Quote:
Originally Posted by pe reivers View Post
I was checking out my 116 today, and had the carb off. (WB27)
Pop-off pressure @ 15lbs, re-seat a mere 10 lbs. That is on the verge of constant leaking.
I stretched the lever spring from 12.5mm to 14.5mm. After that, pop-off was 26lbs, stable re-seat at 16 lbs.
Blowing into the vent hole gave stable carb operation every time.
Keeping the carb at 20lbs pressure, I thumped the carb on the pump cover with clenched fist, My estimate applying about 10G acceleration. (I know from past acceleration experiments, not exactly, so give or take a little). With each thump, carb pressure dropped about 2 lbs, until it stopped doing that at 15 lbs.
Conclusion:
Carb acceleration can take away as much as ~10lbs of pop-off pressure. So if the carb is at 15lbs pop-off, it will very probably start to inject fuel into the engine. The amount injected IMHO is in relation to pop-off values. Dump just a little, or dump the whole plenum chamber content at low pop-off.
This could be it because after the flame out into blender, I obviously dead stick it back to the runway and try to fire it up again. The engine then struggles to start again as if it is flooded. (which it likely is)

I've asked a pal of mine (my karting mechanic from back then) if can borrow his cooling system pressure test gear to test out the carb. Unfortunately my mtb Shock pumps scale does not read low enough to get anywhere near 12-14psi. first notch is 20! Will report back once I have conducted the tests. I'm thinking this gear will be a worthwhile investment going forward
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Old 04-16-2013, 01:09 PM
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Quote:
Originally Posted by pe reivers View Post
Personally, I do not think it is diaphragm pressure related, so no amount of snorkels or similar stuff will improve it. The static ports you have now should do.
Question;??
What is your pop-off pressure? If below 20lbs/in^2 that would explain a lot, together with maybe a high fulcrum lever setting. Beware, lever height can be extremely critical.
+1

Low pop-off pressure is probably it. It would be easy to verify. Extend the metering needle spring a couple of mm and fly. I can almost bet my months salary it wont die in the blender.
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Old 04-16-2013, 02:30 PM
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Pe,

What would be be an acceptable pop of pressure for a WAlbro WT carb?

>20 <30?

or a narrower range? I'm thinking >15 <25. Wat segt u?
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Old 04-17-2013, 04:45 AM
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IMHO, there hardly are limits. I would use at least 20lbs, probably more. There is not much reliable information on pop-off pressure, but since you are picking my brains, here goes:
1) MVVS reported stretching the spring 2mm would help some tuning problems in the WB carb. This carb has a standard pop-off of about 15 lbs. After the stretch, it's at 22 - 25 lbs.
2) Mikuni reports PO values for their pumper could be from 20 - 50 lbs (most WA carbs have ~30+ lbs)
3) Mikuni reports, PO is effective from idle to 1/4 throttle, especially in throttle response from low idle and loading up at low throttle settings. High PO values make for lean acceleration, too low PO values for leaking carbs and blubbering acceleration.
http://www.mikuni.com/pdf/sbn_manual.pdf

In carting, low PO prevents piston seizure when accelerating out of corners! That is why the WB carb has these low 15lbs values. It is a carting carb.

I hope this helps.
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Old 04-17-2013, 05:35 AM
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Excellent, thanks very much!
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Old 04-18-2013, 02:14 AM
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I've learned so much. Thank you guys. Still feel I'm a complete newbie when it comes to carbs.

Are there any instructions on how to set these leavers and springs?
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