Bad carb? (44 IDF)

Not sure whats up with my carb. My left(drivers side) carb is giving me fits. My motor started to backfire out the muffler and the idle is really rough. I was told by a mech. to blow out the idle circuit. The motor ran great. This worked for about a week. Tried blowing it out again. Now the midrange has a huge stumble/hesitation. The carb and motor only have about 400 miles on them. I have a clear in line filter and nothing in the way of dirt or water are visible. And the other side of the motor seems to be ok. so that might rule out a dirty tank as it should clog both carbs. Any ideas from the group? My elevation is 4000 FT. 44 IDF/36mm venturi/ 50 idle jet/165 main/175 air correction. This is on a 171 HP. 2387

Thanks

Jerry, not sure how you blew out the idle circuit. If you blew air down through the idle air opening on top, it may have lodged crap in the idle fuel jet. If it's idling rough too try pulling plug wires till you find the affected cylinder. The idle jet lives behind a screw near the top of the carb and near the top. The jet lives in the back end of the screw (there is an 'O' ring on the screw and it will not come out easily). Jet has a very small hole and plugs easily. Went nuts on mine it was picking up dirt from the top of the carb through the idle air and plugging the works up.
HTH

Jerry,
I had a bad experience with Webers that was ultimately traced back to some water in my gas tank. I first experienced ever worsening performance issues. Finally one carb actually started to leak past the needle and seat with the engine OFF. Short story - water from gas tank (I had earlier run our of gas and sucked god knows what into the carbs). Apparantly Webers (some? all?) have a lot of brass parts inside. Our hard water took awhile to really get the corossion going, but over time it did a real number on the internals. The internals looked like a corroded water faucet from an old house. Hand polished everything, replaced all the replaceable parts and back on the road after flushing the gas tank and adding some denatured alcohol to remove any remaining water. OK since than.

Weber gurus are hard to find. Check any expert's references for satisfied customers before giving them money.

Not sure why! But after much carb fiddling, cleaning and cursing. I started to pull plug wires. And i'll be darned if my #1 cylinder was not firing. Pulled the plug and it looked clean. Bought a new ngk dp8ea-9. Now it's back to normal. That is the first time i have ever had a bad ngk plug. Outwardly nothing looks wrong. Something internal must have broke.

Wow; nice ending! I replaced the NGK plugs in my VS with Bosch (one of them had cracked ceramic insulation); I'll never go back.

165 main? Must be nice to be able to afford getting 8mpg. Sounds like a mosquito fogging machine instead of a speedster.

Try changing the main jet to 140 and the air jet to 200 and you should be good for jetting. Your current 165 mains are fouling plugs like crazy, which is why the plug change made it run so much better. However, the problem is not the plugs it's that pig rich main and air jets.

John
Aircooled.Net Inc.

hi john: to be honest my plugs do not even come close to looking like fouling is taking place. in fact they looked more lean than anything. i could barely tell they had been run. the motor was built and dynoed by chico at CPR. I did buy a bosch O2 sensor and an in car A/F ratio meter. so that should give me a for sure answer on the rich-lean question. it's been really cold. (-36f ) on friday night. So rooting around under the hood and welding in the O2 fitting has not been a high priority project.
But please keep the suggestions coming.

Could it be the intake manifold gasket? That was my problem. Spray some carb cleaner down around the intake manifold. If it balances the idle for a moment it probably means the gasket is torn.

JohnConnolly,
Glad to see you're still monitoring us Speedster guys.
I like your Analogies. I especially like the technical info you and aircool.net make available.
Do you still offer SOC a break on parts? I'm considering the complete hyd clutch kit as seen on aircooled.net. That's gotta be the way to go on any Shortened pan or any VW with heafty Clutch plate. Do you have any user feedback on them?

Regards,
Greg B

if you are lean with a 165 main your floats are WAY WAY off. Which doesn't surprise me since IDFs come with the floats at around 14-15mm. Certain companies clearly just ream jets out, or install huge jets, since this is easier to do then taking the carb tops off and setting the floats. It's critical to know that Weber ASSEMBLES the carbs, THEY ARE NOT SETUP OR ADJUSTED AS SUPPLIED BY WEBER!!!!!

I guarantee you something is wrong, I would check the floats first since this is the most common error. It may seem like a waste of time and $ to set the floats to spec only to put smaller mains in "to end up with the same thing you have now", but the drivability difference is huge. Usually the shops that don't set the floats and just put huge mains in, also have to put huge idles in to cover up the transition hole at 2500-3k that is there with the wrong floats/big mains, the huge idles just cover it up, and kill your MPG. Most guys think that 14mpg is normal since it drives fine, but if you put a wideband on it you'd see that 10:1 A/F is not normal, nor is it good for your plugs and piston rings. It's also worth mentioning that you got the engine setup and dynoed in California, which

1) is at sea level
2) has oxygenated fuel.

So they have bigger jets then in SD just on these 2 facts alone. IOW, by bringing the engine to SD you need to lean it out for the elevation, and maybe the gas too (I would not run gasohol if at all possible).

It's also required to understand that the jets may NOT be what they are stamped. Just because the idle jets say 50, doesn't mean they are 50. One big name vendor (who's name shall be left out to protect them) simply drills the 50 idles to 60s. Customers do not bitch about being too rich, they always complain if they are too lean. This is why the carbs are setup pig-rich when they ship them (less customer service issue). So you must check what you have. At 4k' and 44 IDFs with 36mm venturis, you NEED 52.5-55 idles, 140 mains, and 200-220 airs. If you are using something else, then you have something else wrong that you have not figured out yet.

Last tip: what O2 sensor are you using? If it's a $50-100 narrowband you just wasted your $. You NEED a $350 wideband to really see where your jetting is. We also rent widebands if that's too much coin for you.

I do check in on SOC from time to time, don't post unless I have something worth posting LOL.

I'll give 10% off to SOC members from now to the end of March, if you put "Speedsterowners.com Member" in the special instructions field during checkout. This includes all weber and Mallory stuff. Remember, we setup and jet every weber that leaves our warehouse so you don't have to. Nobody else does this (it's a pain LOL). Out of the box Webers are almost unrunable, but people assume they are "OK because they are new". Nothing could be further from the truth.

PS: that hydraulic clutch kit is awesome!

John
Aircooled.Net Inc.

Thanks again john: The sensor is a bosch 13913 i obtained it from a weber dealer in calif. I beleive it's called race tech. i have a few alt. idle and main jets i bought from a supplier in italy. i have a set of 45-50-55 idles. cpr had 50's in it. I'll go to aircooled and order some more jets per your recommendations.

Thanks again

If the A/F meter was under $300 it's a narrowband and a waste of time AFAIAC. Remember, just because a jet is stamped X doesn't mean it's an X jet, because drilling/reaming is rampant. I cannot overemphasize the importance of fuel pressure (3-3.5psi) and float levels. You are wasting your time "jetting" if you have not set the floats YOURSELF.

John
Aircooled.Net Inc.

Thanks john: I checked the floats and they were at 15MM top and 25MM drop. I adjusted the floats to 10MM and 30MM. took out the 165 main jets put in 150's. removed the 170 air jets and put in 185"s. and left the 50 idles. I still need to tweak it with the jets i ordered from air cooled. But the diff. was profound. the stummble is gone. it started up much easier. and idles smoothly at about 1000 rpm. i will try the 145 mains/55 idles/200 air jets when i get them and let the group know how that works. and adjusting the floats was very easy. the hard part was removing them from the car. I would say to the group. adjusting your floats is a very easy but important first step in tunning your weber carbureted motor.

Jerry,John,
Thanks for the follow up.
I'm chasing a problem on my 44 idfs.I don't know the history of these carbs as I got them used. They're the older ones that have the cam driven accelerator pump. They had been setting around for an undetermined length of time. (years)
My problem is that the pump jets dump fuel on acceleration or when you rev. the motor. You can see them dribble on anything off idle.
I've replaced the exhaust jets for the accelerator pump with "O" jets (plugs) to eliminate fuel being drawn from that source. Made sure that the accelerator pump linkage has the correct clearance. set the float levels and checked all the jets to verify that they're at least "in the ball park"
I think my problem is check valves for the pumps. An exploded view of the carbs lists the screw that holds the pump jets in as Pump Demand Valve. I think that's where the check valve is.

Any experience with these? I'll follow up when I determine what the problem is/was. But in the mean time, has anyone had this problem? And what was the resolution?

My other motors have dellortos. This is my initiation to the world of Weber.

Thanks,
Greg B

Jerry, at your elevation you'll probably need 50-52.5 idles. I'd go with 50-52, 135-140, 200-210, F11. Did I call the floats being off or what? I even told you what they were set at, LOL. BTW, weber spec is 10mm, but you'll find the carbs work better if you set them to 11-11.5mm.

It astounds me how ignorant some "experts" are on these things, absolutely blows me away. You had these "tuned" on a dyno, right? 165 mains? Like I said, mosquito fogger.......

Also, we have a more detailed carb tuning article coming up soon in our tech section, explaining why float level is so darned important. Carbs are not complicated. 98% of the reason people get fed up with Webers is stupid; it's Float Levels being wrong, Fuel Pressure being wrong (usually too high), and dirty carbs (using cheap fuel filters, or dirty air bypassing the air filters and clogging up the idle circuits (which DO have air in them BTW, that's how the dirt gets in there). BTW, the chrome fuel pressure "regulators" with the dial on them should be thrown in the trash, unless you like chasing mysterious carb issues. A good regulator is $35.

I can't explain it any more clearly then to say if you have webers you must be sure the floats and fuel pressure are set. And when I do this, over half the people I tell do not do it and continue to chase around making jet changes, and wonder why the carbs won't tune. It is very very frustrating that most people (not you Jerry) will simply not listen. "Just bolt em on and run em" is what most places say, and while they do "run", they run like shite AFAIAC. Most guys have no clue how they are supposed to run/drive because most guys have been driving around on carbs that are totally jacked up, and don't even know it.

Greg,

give acevw@aol.com (Art Thraen) (801) 943-1234 a call on that problem. I'm not familiar with the older IDFs, but he sure is and will be able to help you out.

John
Aircooled.Net Inc.

I received the jets i ordered from aircooled. after installation the car is running even smoother. much more responsive. runs through the rev range quicker. all in all the motor seems to like NOT being on the verge of flooding all the time. i imagine i'll be getting better fuel mileage to boot. final specs are 44 idf's 36 venturies. on a 171 hp 2387 at 4000 FT. elevation. 50 idle jets / f-11 emultion tubes/ 200 air jets/ 145 main jets/ floats set at 10-11MM top/ 30MM drop.
Mr. Connolly was right. It is absolutely critical to FIRST set your floats. then the carbs will respond properly to jetting changes.
Many thanks to the group and ESP. Mr. Connolly at aircooled.net for all the help.

you are still too rich; remember 135-140 main. 140-145 main is for sea level, not 4k'. The engine will run even better the closer you get to "right", and you are one step away IMO.

Vac advance is another significant improvement, but we'll leave that for another thread LOL.

John
Aircooled.Net Inc.

I agree john. As soon as i get out of SOC i will jump over to aircooled.net and order 135 & 140 mains, and 210 or 220 air jets or both. my dizzy is the non vac advance uni-lite. i may change that in the future. but i have been spending to much money on fuel and weber jets as of late. so vac. uni-lite will have to wait

Thanks again

John,
Need yourjetting recommendations.. gas mileage is 14 MPG in town. Engine loads up at lower RPM. What jets would you suggest? Altitude in Austin TX is approx 500 ft. Engine is 2110 cc, with 44 MM webbers.Idle jets are 55, main 155, airjets are 200. Appreciate your help and comments!
Thanks,
Bob Miller

Bob,

need venturi size and emulsion tube.
Also, remember you MUST MUST MUST get the fuel pressure to 3-3.5psi, and set the floats before you jet. Also a 009 or cent only distributor will cost you 3-5mpg.

John
Aircooled.Net Inc.

John,

Here are carb specs:
Dual 44 IDF webbers, Idle jet 55, Main jet 155, Air jet 200, Emulsion tubes F-11.

Distributor is Bosh 009 mechanical advance. Ignition MDS-6A with 8 mm HP wire set. Timing set at 12 deg. BTDC at idle. 34 deg. BTDC maximum.

Hopefully this will enable you to make jetting recommendations.

Thanks

change your main to 140, back the ignition timing down to 30 total.

The rest is fine, but you must check floats and fuel pressure, we can't do that for you.

John
Aircooled.Net Inc.

John,
Thanks for the advise. Will set up carbs as recommended.
Bob Miller