well I been trying to do some searching without turning up much useful info but know lots of people on here are very knowledgeable with weber IDF's, so maybe someone can help! On a cold motor I've gotta pump the gas SEVERAL times for it to fire up. And when it does fire up it is VERY cold collared and doesn't like "take" throttle very well until it gets warm. It wants to pop and cough when cold, isn't this a sign of being lean? When it gets warmed up it takes throttle pretty good other than a small "blip" when you throttle it hard. About everywhere I looked I found pretty similar suggestions as far as jetting a single 40IDF for 1600 DP. I'm running a 55 idle, 130 main, 200 Air correctors, 50 pump exhaust valve, 28mm venturi. correct me if wrong,but if your mixture screws are out further than 1 turn you need to go bigger on your idle jets right? how it acts on a cold motor compared to when it warms up is daylight/dark. Given, the timing is prob set about 2-4 degrees higher at 3000rpm than it should be from what I've read (its at about 34 degrees). Also the temp has been in 50's outside when I've been running/tuning it and currently do NOT have preheat going to it although i keep reading it's pretty much a MUST. I'm up for any suggestions or opinions to steer me in the right direction! Thanks guys

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--WHEN IN DOUBT, THROTTLE OUT!!!--

ive seen people run the airscrews up to 2 1/2 rounds out but I prefer to keep them between 1 - 2 rounds out

and as for timing each motor has its own sweet spot but most end up around 30 or 32 at 3500

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Just Stand On It!!!!

Chris

snail rail yours sounds like mine. I'm running a 40idf to and I'm haveing the same problems to but I have changed some of my jets but I can't remember to what now I will have to get it out and check them. There are some kits out t here that they say will help cure the idf tunning issues but theyare around 120 If I remember right

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If its on the internet its got to be true they can't put any lie's on the internet

sounds just like mine.i tried all kinds of jets not much change.i just learned to live with it after it warms up it runs fine.

Air Cooled engines are cold natured and need to warm up. Also a 40 IDF has no choke and that affects the performance until it warms up. You really want to tune an engine at operating temperature.

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Water Cooled Consortium, Chairman of the Build (Former AC purist)

well tried taking it out last night and try it out and needless to say it's not right. It's a lot better when it warms up but still it coughs and pops when you throttle it. Tried dropping the 130 mains to 115's but was significantly worse. So put the 130's back in and swapped the 200 air correctors for 190's and it also got worse. so got fed up and stopped for the night.... pulled #1 plug and it definetly doesn't look too rich at all. The right mixture screw is pretty much unresponsive. You can run it all the way in and the motor rpm will barely drop. But the left side mixture screw seems right (will try to die when running it in). Would this point to a vacuum leak? I sprayed starter fluid all around the intake boots and carb gaskets and everywhere else without any change... when it warms up you can grab the throttle and it still stumbles a lil but when you try to drive it, if just giving it a little throttle its ok but any further it stumbles and falls on its face. Help???

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--WHEN IN DOUBT, THROTTLE OUT!!!--

a single carb needs a small hole ( 1.5mm if I remember correctly ) drilled in each of the butterfly's and they tend to run bigger idle jets than dual carbs. as long as there are no issues other than jetting, the stumbling problem is most likely the idle circuit, so you need to get that right before even fooling with the main and air jets

also on occasion a single carb may need a " 0 " pump jet and sometimes even the "squirters" need to be bigger and other times a simple "pump rod" adjustment can smooth things out

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Just Stand On It!!!!

Chris

I love fuel injection more every time I read a thread like this! Try not make to many changes at one time getting a single to run with out a small hesitation is difficult I know some of the Alabama gang are running singles with great success. Perhaps one of the Alabama gang will chime in. Best luck with it dude just don't get discouraged you will get it to work it takes time.

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Water Cooled Consortium, Chairman of the Build (Former AC purist)

drilling the small hole in mine helped more than anything.its a 44 weber on a 1835

cb performance says 2mm hole
http://www.cbperformance.com/SearchResults.asp?Cat=152

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Just Stand On It!!!!

Chris

the right side being unreponsive is the question what kind of ignition you useing points or electronic?

Drilling the hole allows you to close your throttle blades far enough to get back into the idle circuit. If your blades are open to far to let it idle your idle mixture screws will be useless. If your blades are open past the transition circuits you will have a bad stumble. Sounds to me like that's what you have going on.

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If it ain't broke ill fix that

I second drill the throttle plates i did that to mine and it made a big differance

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If its on the internet its got to be true they can't put any lie's on the internet

yes on a single carb you need to drill the holes. and i do noy have a heat riser on my carb either. i think mine runs a little on the richer side, but also think it makes it run better

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ANTI- antifreeze!!!!!!

Where exactly do the 2mm holes need to be drilled? In the throttle blade itself? I'm running electronic ignition btw. I can back idle speed adjuster all the way out and it still idles, that's how I have it adjusted as it sits. I adjusted the carb according to the instructions from weber's website. I'm going to order some idle jets and try to go a little bit richer on them. Since I'm running 55's, I was thinking some 60's & 65's? one of the 2 sets should get me closer I think. Or should I try drilling the 2mm holes first? It idles good and has pretty good throttle response if I grab throttle. but when driving it and putting it under a load its got a spot around mid throttle where it'll cough and spit for a sec but will eventually clear out if I push it on down full throttle. I adjusted acc. pump and it's running better than it has since putting carb on but still not acceptable due to that hiccup at mid-range

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--WHEN IN DOUBT, THROTTLE OUT!!!--

it should die out with the idle screw not touching, sounds like you may have throttle cable to tight, air leak, a twisted throttle shaft, or the butterflies are not properly centered in the hole

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Just Stand On It!!!!

Chris

it idles real low if backed all the way out but will still idle. I've yet to find any vacuum leak as I've sprayed starting fluid around intake boots and all around carb. I ordered some idle jets & from what all I've read the idle circuit is what you drive around on 90% of the time and it'll never be right until you get it right. I appreciate all of the help so far guys and I'm still trying to be patient with it!! I read quite a bit bout these carbs before buying a new one and knew that there was going to be quite a bit of tuning/jetting required before getting it right but I can already tell a big difference in overall driveability in the woods big time compared to the weber progressive I was running. After running it for a little while I stopped and pulled a plug real quick and it's not rich by any means. And from what everyone has said you have to run idle jets bigger when running a single IDF. Maybe 60's or 65's will get me closer. Is it true that the air corrector jets don't come into play until 4000rpms and up? Thought that I read that on aircooled.net

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--WHEN IN DOUBT, THROTTLE OUT!!!--

http://www.myvwsite.com/webers2.html look at this as well, might help! the hole goes in the butterfly plate down in the carbs, really need to drill from the bottom with the carb off. im trying to find the page for you that shows it. i would go out and look on mine but its under a tarp. tied to the trailer with an inch of snow on it and a big muuddy ass swamp all around it........... oh and you MUST buy a set of jet doctors to run on it or youll be cleaning idle jets all the time

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ANTI- antifreeze!!!!!!

http://www.cbperformance.com/ProductDet ... tCode=3122 i also bought this setup so the throttle cable does not run thru the shroud it comes up over the top and attaches to the carb base plate. i hated that linkage that comes with the carb, might want to consider this aswell this with the jet doctors, along with an outerwear and an appropiate family dollar garbage can or i think i used a rubbermaid tub of some sort and painted it. i never ,well very rarely have to clean my idle jets. jsut trying to save you the head aches i went thru. oh and i did not find the picture, but the 2 - 2 mm holes that you drill in the throttle plates go facing the rear of the engine NOT toward the shroud side. between the center and 6 o'clock.

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ANTI- antifreeze!!!!!!

http://www.cbperformance.com/ProductDet ... tCode=7557 link for the jet doctor kit... oh and you might as well buy velocity stacks while your at it good luck man hope some of this helps you !

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ANTI- antifreeze!!!!!!

so the (2) 2mm holes drilled are actually in the throttle blades? I been trying to find a picture of doing it but no luck. I managed to come up with a drill here at work 2nite and was going to do it when I got home (here in about an hour). or is the 2 holes that are drilled described in the instructions for the jet doctor a totally different procedure? Thanks big time diamonddave! for the help man! I'll go ahead and get that ordered tomorrow hopefully. When I read here saying to drill throttle plate and when I read on cbperformance website I'm taking it that you're suppose to drill the actual throttle butterflies. Correct me if wrong?!

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--WHEN IN DOUBT, THROTTLE OUT!!!--

yes the brass throttle plate is what gets the 2mm hole

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Just Stand On It!!!!

Chris

have you read the tech art.on aircooled.net they have a very good one on jetting.

yes holeman I did read it (a few times actually...) and it is a great writeup. I'm getting a better understanding of how it all works finally. I'm starting to see where a lot of people (including myself) make mistakes on these carbs by not starting with the idle circuit and getting it right before ANYTHING else. From what I've read from aircooled.net and weber tuning guide mine acts to be lean on idle circuit but seems like my current jetting would be more than enough. How often do the air bleed screws get adjusted on just a single carb setup? All the tuning guides and tech articles I've read pretty much say to leave these alone?

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--WHEN IN DOUBT, THROTTLE OUT!!!--

from all i have read they all say to leave those to experts.