Those aren't idle adjustment screws, they are air bypass screws. Carefully remove the needle screw and make sure you have the green rubber "O" ring for the needle screw. Blow some compressed air into the passage and clear it out.
You're supposed to screw the bypass screws in gently until the engine stumbles and or makes popping sounds then slowly screw them out until the engine runs smooth.
Your idle adjustment screws are located on the narrow end of the carburetor usually where the linkage attaches
Felix.....I can't swear to it, but if the butterflies are not dead even over the transition ports, you can get weird readings and action.......If you have Bob Tomlinsons Weber Manual, there is a brief paragraph that gives some ideas of what to expect.......Some of my most recent problem was most likely related to this area........
The C.B.Perf. rebuild kits warn you to back off the idle speed screws them run them in no more than 1/2 turn after they make contact with the throttle shaft lever......This is a base line that should have the butterflies in the correct position +/- a minute fraction......
I have idle mixture screws that don't respond immediately, but will function....I just have to listen closely and pay attention to the tach...... ( easy for me, I drive a Spyder.)
Hopefully Danny P. will drop in and give you some additional help...If not, send him an e-mail.
The C.B.Perf. rebuild kits warn you to back off the idle speed screws them run them in no more than 1/2 turn after they make contact with the throttle shaft lever......This is a base line that should have the butterflies in the correct position +/- a minute fraction......
I have idle mixture screws that don't respond immediately, but will function....I just have to listen closely and pay attention to the tach...... ( easy for me, I drive a Spyder.)
Hopefully Danny P. will drop in and give you some additional help...If not, send him an e-mail.
Larry and Leon - Thanks for the feedback. By "idle screw" I meant idle mixture screw, not the air bypass screws. These are the spring loaded screws with knurled heads for adjusting by finger. I just read the adjustment procedure in the IM owner's manual, and it says the idle jets may be clogged if there is no change in idle speed when the idle mixture screw is fully closed. I'll try pulling them out and clearing. I haven't touched the carbs in two years of driving the car, so it wouldn't be too surprising if the jets need some cleaning.
Felix, pulling those needle screws out and cleaning them is a good idea, but in my experience the idle jets must be removed, cleaned and also I use some compressed air to blow through the passages between the jets and the needle screws. I use a can of air like used to blow computers clean. The little straw will fit into the idle jet opening in the carb and into the needle screw hole. Give it a nice burst from both ends. Be care full with the little o-ring on the jet and the screw and the small metal ring. Good luck! I highly recommend getting Tomlinson's Weber book from CB Performance. It will make all the issues clear, at least it did for me.
And if you can't find a can of compressed air for computer cleaning, just use a can of carb cleaner with on of those little red tubes on it. Stick the tube into the mixture screw hole and give it a really good blast and then down the jet hole (with the jet out). Blast the hell out of the jets while they're out, too.
You know, I was just thinking - I ran autolight/holly 2500's on my Mustang for almost a decade and never had to clean a jet.
I'm jus' sayin......
You know, I was just thinking - I ran autolight/holly 2500's on my Mustang for almost a decade and never had to clean a jet.
I'm jus' sayin......
Will - I'll get Tomlinson's book - thanks for the suggestion.
Will & Gordon - Just to be sure I'm clear on what you guys are describing, are you saying I need to blow out the passages in the carburetor body itself, in addition to blowing out the jets themselves? Is so, do I need to remove the carbs to blow out these internal passageways? Should I order a rebuild kit at the same time I get the book? Down here in Louisiana, there are not many vendors selling anything for aircooled engines and/or carburetor applications. It seems that every time I get into a small maintenance job, I order the parts I think I need, wait a week or more for them to come in from the West Coast, and then as soon as I resume the job, quickly discover I need one more little part to finish (wait another week, etc......). A simple little job can lead to a few weeks of downtime. Oh well, I guess that's all part of the fun.
Will & Gordon - Just to be sure I'm clear on what you guys are describing, are you saying I need to blow out the passages in the carburetor body itself, in addition to blowing out the jets themselves? Is so, do I need to remove the carbs to blow out these internal passageways? Should I order a rebuild kit at the same time I get the book? Down here in Louisiana, there are not many vendors selling anything for aircooled engines and/or carburetor applications. It seems that every time I get into a small maintenance job, I order the parts I think I need, wait a week or more for them to come in from the West Coast, and then as soon as I resume the job, quickly discover I need one more little part to finish (wait another week, etc......). A simple little job can lead to a few weeks of downtime. Oh well, I guess that's all part of the fun.
Felix, you can clear the passages with the carbs installed. Remove the needle screws, remove the idle jets. Then using the little red straw on air or carb cleaner insert into hole where jet was removed from. It is a "find the hole by feel" situation or use a small mirror to get it in hole. Send a nice blast into the hole and it will exit out the needle screw hole . As long as you are ordering from CB Performance, a set of Jet Doctors might be a good idea. I have not used them yet, but I will be putting them in soon. The dirt that gets into the idle passages comes from the small air intake for these passages. These Jet Doctors http://www.cbperformance.com/weberjetdoctor.html are a possible solution to this annoying problem. I have no personal experience with them, but am installing a set in the near future.
When you order the book, order a couple of carb rebuild kits for your respective carbs, too. They're relatively cheap and will probably come in handy somewhere down the road and, while you don't need them now, you'll probably need them eventually and then you'll already have them "in stock".
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Before even thinking about carbs, people sometimes need a reminder. This assumes a mechanically healthy engine: good compression, broken in, and no leaking valve seals and/or rings. First and foremost, adjust the valves!!!!! This cannot be stressed enough. Next the ignition system must be 100% and timing adjusted properly. Third, make sure you have plenty of clean fuel at 3-3.5 pounds. Fourth, linkage needs to have NO SLOP and downlinks need to be at EXACTLY the same angle.
Then we can finally start talking about carbs....so many times things are wrong and it isn't the carbs fault at all, it is fuel, pump, ignition, linkage, and on and on.
On the carbs, if you're sure of all the above, first sync idle air(linkage disconnected) using idle speed screws, idle bypass screws closed. I only open an idle bypass to compensate for one cylinder a little low. Then cruise air(raise speed to 2500-3000 and recheck air sync readings). The first part verifies even air through all the throats, the second indicates if your linkage is good off the idle stops, which it always is when you're driving.
Mixture screws are the last thing to be touched, but once mixture is set the idle stop screws usually need to be re-adjusted. It is a sort of a dance, that while frustrating at first, becomes second-nature and a pleasure with practice. This reminds me of my first bra-unhooking(didn't think I would ever get that thing off), now I can do it with one hand easily!
RE idle jets: haven't had to blow one out for quite some time, nor touch a screw. I think last year after Carlisle I had some crap in a float bowl, but that was it, about a year ago. Clean fuel and clean air is the key. And drive it as often as you can, sitting gas in carbs is the enemy, keep it flowing.
Felix, email me your number if you want to chat about this, my email is in my profile.
Then we can finally start talking about carbs....so many times things are wrong and it isn't the carbs fault at all, it is fuel, pump, ignition, linkage, and on and on.
On the carbs, if you're sure of all the above, first sync idle air(linkage disconnected) using idle speed screws, idle bypass screws closed. I only open an idle bypass to compensate for one cylinder a little low. Then cruise air(raise speed to 2500-3000 and recheck air sync readings). The first part verifies even air through all the throats, the second indicates if your linkage is good off the idle stops, which it always is when you're driving.
Mixture screws are the last thing to be touched, but once mixture is set the idle stop screws usually need to be re-adjusted. It is a sort of a dance, that while frustrating at first, becomes second-nature and a pleasure with practice. This reminds me of my first bra-unhooking(didn't think I would ever get that thing off), now I can do it with one hand easily!
RE idle jets: haven't had to blow one out for quite some time, nor touch a screw. I think last year after Carlisle I had some crap in a float bowl, but that was it, about a year ago. Clean fuel and clean air is the key. And drive it as often as you can, sitting gas in carbs is the enemy, keep it flowing.
Felix, email me your number if you want to chat about this, my email is in my profile.
Thanks, again for all the good info. I ordered a couple of Weber rebuild kits just to be sure I'll have any orings or other bits I might end up needing, and also ordered Tomlinson's book.
Danny - I remember watching your expert tuning handiwork on Jack's car and committing the procedure to memory. It mostly followed what's been posted on this site and in a couple of other manuals I've read, but you threw in a few extra wrinkles that are quite nice (e.g. blipping the throttle after an adjustment seems to have been dialed into the sweet spot, and verfiying things are still dialed in after the engine settles back down, etc.). I'm pretty sure I've got a couple of clogged idle jets, because the two corresponding mixture screws have absolutely no impact on engine idle, even with gross adjustments. The troubleshooting guide in my IM owner's manual says that such behavior usually results from a clogged jet.
Danny - I remember watching your expert tuning handiwork on Jack's car and committing the procedure to memory. It mostly followed what's been posted on this site and in a couple of other manuals I've read, but you threw in a few extra wrinkles that are quite nice (e.g. blipping the throttle after an adjustment seems to have been dialed into the sweet spot, and verfiying things are still dialed in after the engine settles back down, etc.). I'm pretty sure I've got a couple of clogged idle jets, because the two corresponding mixture screws have absolutely no impact on engine idle, even with gross adjustments. The troubleshooting guide in my IM owner's manual says that such behavior usually results from a clogged jet.
Megasquirt it and your troubles will go away
I have neen emailing back and forth with Art Thraen---he would be willing to run a Weber seminar in early Sept for folks who want to learn how to manage their Webers. I am up for this to the max!!
Art is the recognized expert in Webers----period. Who better to handle such a seminar?
I am going to sign up because there is absolutely no one within 500 miles of me who knows Webers. I do my service, oil ,valves and a lot of other stuff----but I am a big "newbie" when it comes to Webers.
I want to know how to set the floats, how to sync, how to adjust the Mixtrue controls and also those mysterious air jets to have carbs that w-o-r-k without all the mystrey that Leon is going through.
The seminar would be 1/2 day----maybe a bit more more and after that, someone should understand what the hell is going on with their carbs. Art is in Salt Lake City, Utah--I would fly over. I don't know the cost but the more participation, the less per person the cost will be.
Any interest??
---Back to Leon's thread!
It would be great if this could be live, online, for us distant folks.
Distant? You are closer than I am. I plan to do this myself but if others want to get educated on maintaining their carbs this would be the ticket.
I envy Leon who can handle all these avenues for getting his carbs back to perfection but I just don't have the 20 years available to learn it piece by piece.
Anyone else interested in heading over to Art's place in SLC?
I envy Leon who can handle all these avenues for getting his carbs back to perfection but I just don't have the 20 years available to learn it piece by piece.
Anyone else interested in heading over to Art's place in SLC?
Maybe we could convince him to join us in Asheville in October.
Regarding Webers, I can summarize my experience with by listing the key things I've learned about keeping them happy.
1. A clean, smooth, properly adjusted linkage. I REALLY like the new CSP bellcrank setup, but the crossbar with the heim joint fix works well, too.
2. Properly adjusted floats. It's really pretty easy to do - even I can do it.
3. Two clean fuel filters.
4. Clean gas. This is obvious, but you can get crap from some gas stations, or you can have crap in your tank. Either will cause problems, but can be avoided. Maybe put in some fuel system cleaner once in a while. If you can find gas without ethanol, so much the better. The ethanol will degrade the diaphrams in the accelerator pumps over time.
5. Rain hats. Ask me how I know.
6. Jet Doctors. Simple, cheap, and effective.
7. A really good, proper tuning and synchronization. This is not as big a deal as many think. I watched Danny Pip do mine in about 20 minutes. The difference is amazing. Once tuned, keep the crap out of 'em and you're good to go for a long time. I now own a synchronizer and feel confident enough to use it.
Since Carlisle I have removed the carbs and replaced the crossbar linkage with the bellcrank without messing up to the tune Danny put on the carbs. Once dialed in, they are actually less fragile than many think.
Regarding Webers, I can summarize my experience with by listing the key things I've learned about keeping them happy.
1. A clean, smooth, properly adjusted linkage. I REALLY like the new CSP bellcrank setup, but the crossbar with the heim joint fix works well, too.
2. Properly adjusted floats. It's really pretty easy to do - even I can do it.
3. Two clean fuel filters.
4. Clean gas. This is obvious, but you can get crap from some gas stations, or you can have crap in your tank. Either will cause problems, but can be avoided. Maybe put in some fuel system cleaner once in a while. If you can find gas without ethanol, so much the better. The ethanol will degrade the diaphrams in the accelerator pumps over time.
5. Rain hats. Ask me how I know.
6. Jet Doctors. Simple, cheap, and effective.
7. A really good, proper tuning and synchronization. This is not as big a deal as many think. I watched Danny Pip do mine in about 20 minutes. The difference is amazing. Once tuned, keep the crap out of 'em and you're good to go for a long time. I now own a synchronizer and feel confident enough to use it.
Since Carlisle I have removed the carbs and replaced the crossbar linkage with the bellcrank without messing up to the tune Danny put on the carbs. Once dialed in, they are actually less fragile than many think.
Lane - Count me in for any Weber clinic you manage to set up with Art, whether in SLC or NC. The more advance notice, the easier to free up time in the schedule, but I'll definitely make time for this one!
Jack's the one who's been talking to him. I would love to have Art join us in Asheville, but I doubt that it's possible unless we all pitch in to pay his way, which would probably be pricier than everyone would want to do. Jack, float the Asheville idea past Art if you want, but the SLC venue is more likely. I'm afraid I wouldn't be able to travel that far for a carb clinic. The "personal bid'ness manager" would have a fit.
Lane, glad you're running well. I agree with all you've said, and it is true, once they're dialed in and clean fuel is fed to them, they are trouble free.
Jack, I don't have anywhere near 20 years of experience with carbs, let alone Webers! I have only had a couple of carbureted cars, and they were all singles. The Spyder is the first multi-carb setup I've had. I have had it on the road for 5 years, but all the tweaking was done the first year or two, most of it learning as I went.
Leon, keep running.......
Jack, I don't have anywhere near 20 years of experience with carbs, let alone Webers! I have only had a couple of carbureted cars, and they were all singles. The Spyder is the first multi-carb setup I've had. I have had it on the road for 5 years, but all the tweaking was done the first year or two, most of it learning as I went.
Leon, keep running.......