I need to know more about adjusting my Weber carbs, so I decided to practice on mine. It would appear that my mixture screws are adjusted much leaner from what I
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I need to know more about adjusting my Weber carbs, so I decided to practice on mine. It would appear that my mixture screws are adjusted much leaner from what I
Buy "Bob Tomlinson's Weber Tech Manual" Super tune-up guide for VW
and Porsche engines. I think CB Performance www.cbperformance.com
I have the book and it great
Check your hex bar play. There should be no up-down or back-front play. The side-to-side play should be no more than 1/8". If you suspect excessive play, pull the hex bar off and check it. Check with www.pelicanparts.com, www.redlineweber.com, www.aircooled.net and www.cbperformance.com. These sites all have good tech articles on carbs and other stuff. CB Performance sells new hex bars and the stud bolts the hex bar rests on. If you buy the new stud bolts, make sure you buy new springs and grease the interior of the hex bar, the springs and round end of the bolt liberally. The hex bar offered by CB is made of steel. Total cost for the whole shebang is probably around $20.
Hint: make sure the arms from the hex bar to the carb is vertical, and mark its position with a permanent marker before you remove the hex bar. This will help you make sure the bars are in the same position as before their removal. After the hex bar is replaced, put some small hose clamps on either side to prevent any movement (the small allen screws can strip if you tighten them too much). Hose Clamps might look hokey, but they work and are cheap. This is a really easy job, even for a novice like me. Takes about 20" (longer if you have some good red in a paper cup).
Hint: make sure the arms from the hex bar to the carb is vertical, and mark its position with a permanent marker before you remove the hex bar. This will help you make sure the bars are in the same position as before their removal. After the hex bar is replaced, put some small hose clamps on either side to prevent any movement (the small allen screws can strip if you tighten them too much). Hose Clamps might look hokey, but they work and are cheap. This is a really easy job, even for a novice like me. Takes about 20" (longer if you have some good red in a paper cup).
Well Barry you were so very close, too bad I was not able to close the loop on my own but Larry Jowdy did.
For those of you with Spyders that are running great, this will not be of interest, for those that think the reason for a poor running motor maybe electrical or fuel delivery this may interest you. My car ran fine under full acceleration but when just driving along at a constant speed or slowly starting to accelerate, the car would sputter gurgle and vibrate until full throttle would make me forget that annoying steady state engine behavior. Thinking it must be dirt getting into the idle jets I cleaned them religiously, nothing changed. Now rotor and distributor wires, plugs, the annoying symptoms remained. The Solution, a trip to the Jowdy compound in Ontario CA and finally a resolution. When pushing down on the hex bar every so slightly the linkage on one carburetor was ahead of the other just enough to cause the carbs to out of balance; one was getting more fuel than the other in the early part of accelerating. Once the accelerator pumps opened up for full throttle none of that vibration and uneven running was noticeable. I finally have car that runs like it should. Thanks you Larry!!
For those of you with Spyders that are running great, this will not be of interest, for those that think the reason for a poor running motor maybe electrical or fuel delivery this may interest you. My car ran fine under full acceleration but when just driving along at a constant speed or slowly starting to accelerate, the car would sputter gurgle and vibrate until full throttle would make me forget that annoying steady state engine behavior. Thinking it must be dirt getting into the idle jets I cleaned them religiously, nothing changed. Now rotor and distributor wires, plugs, the annoying symptoms remained. The Solution, a trip to the Jowdy compound in Ontario CA and finally a resolution. When pushing down on the hex bar every so slightly the linkage on one carburetor was ahead of the other just enough to cause the carbs to out of balance; one was getting more fuel than the other in the early part of accelerating. Once the accelerator pumps opened up for full throttle none of that vibration and uneven running was noticeable. I finally have car that runs like it should. Thanks you Larry!!
This should be of interest to those of you who use a hex bar to connect your carbs. These hex bars ARE the problem. Soon after Larry fixed the carb sync problem mentioned in the thread above the same carburetion problems started all over again. As some of you may have read Larry Jowdy and some of the other shops like Vintage, is now making a permanent repair to this problem,call them for a permanent fix, you won't be disappointed.
Another solution to the issues that many have had with the hex bar carb linkage is to dump it and use a bell crank method of carb hook up.
I have had many hex bar issues following me over several engines and several cars. No matter how much tuning I did, or what I used for bearings in the pivot points, the carbs did not stay in sync for more than a few hundred miles. I am a reasonably handy person who has a small machine shop to play with....and to be blunt I have spent a lot of time attempting to "improve" the problems of hex bar kits.
To make a long story a bit shorter the bell crank set up was not cheap, it is German made, pivots on ball bearings. But, the carbs, I have sync'ed them once, and they have stayed sync'ed since, and I am over 2500 miles with this solution. The only problem I see at all is that of the idle speed changing from a cold engine to hot. It goes up as the engine expands. So, I idle at 500 cold and 950 hot....I don't like it but everything stays sync'ed.
By the way, I think one of the big problems with the hex bar linkages has to do with the geometry betweem the carbs...even with Heim joint bearings the geometry between the 2 carbs is asymetrical with most kits, meaning the throttle plates do not advance at the same rate from idle to full throttle. By the way, the Heim joint repair does solve one of the bigger problems, just not the geometry problem.
I have had many hex bar issues following me over several engines and several cars. No matter how much tuning I did, or what I used for bearings in the pivot points, the carbs did not stay in sync for more than a few hundred miles. I am a reasonably handy person who has a small machine shop to play with....and to be blunt I have spent a lot of time attempting to "improve" the problems of hex bar kits.
To make a long story a bit shorter the bell crank set up was not cheap, it is German made, pivots on ball bearings. But, the carbs, I have sync'ed them once, and they have stayed sync'ed since, and I am over 2500 miles with this solution. The only problem I see at all is that of the idle speed changing from a cold engine to hot. It goes up as the engine expands. So, I idle at 500 cold and 950 hot....I don't like it but everything stays sync'ed.
By the way, I think one of the big problems with the hex bar linkages has to do with the geometry betweem the carbs...even with Heim joint bearings the geometry between the 2 carbs is asymetrical with most kits, meaning the throttle plates do not advance at the same rate from idle to full throttle. By the way, the Heim joint repair does solve one of the bigger problems, just not the geometry problem.
Jim I will concur with your statement regarding the opening and closing of the throttles but are you sure it's a geometry problem rather than a flex problem? After repeatedly playing around with the hex bar linkage, I have found that the position of the throttle cable arm plays a massive role in the opening of the throttles. If the throttle cable linkage arm is closer to one carb, that carb will open sooner (almost impossible to detect) but it will open sooner. Proper adjustment of the linkage with the addition of the rod end bearings seems like a great, easy and relatively inexpensive alternative.
Good morning Larry,
In my case it was geometry, not flex, after I solved the flex problems as well as the wear problems. I recognize there are many versions of hex bar linkages, I have only ever had one where the geometry between the left carb and the right carbs was identical. In that case the manifolds were offset so that both carbs were on the same front to back plane. The differences in geometry can be seen by putting a small but accurate angle guage on both butterflies....on my CB performance hex bar set up as well as a recent Empi, there is more than a 20 degree difference between open and closed throttle. Hard to see unless you have a small but accurate angle gauge. I made 2, one for each carb using a scale on a piece of .025" brass with a tiny plum bob on each...I will see if I can find them around here and will send you a photo if and when I do find them. The differences can be measured open and closed but it is not a clean nor graceful process. Butr it proves the point on my set up.....
In my case it was geometry, not flex, after I solved the flex problems as well as the wear problems. I recognize there are many versions of hex bar linkages, I have only ever had one where the geometry between the left carb and the right carbs was identical. In that case the manifolds were offset so that both carbs were on the same front to back plane. The differences in geometry can be seen by putting a small but accurate angle guage on both butterflies....on my CB performance hex bar set up as well as a recent Empi, there is more than a 20 degree difference between open and closed throttle. Hard to see unless you have a small but accurate angle gauge. I made 2, one for each carb using a scale on a piece of .025" brass with a tiny plum bob on each...I will see if I can find them around here and will send you a photo if and when I do find them. The differences can be measured open and closed but it is not a clean nor graceful process. Butr it proves the point on my set up.....
I have found the same as Larry: The relatively long skinny hex-bar will twist against the spring pressure counterforce of opening the carbs.
Just by luck, my throttle cable arm is almost dead-center on my hex-bar. After I have balanced my carbs for idle and just off-idle I can pull on the throttle cable and the RPMs will increase smoothly.
However, if I increase throttle by pushing down on the carb actuating lever on one end of the hex-bar, the RPMs will increase quite roughly because (I've presumed) the hex-bar is twisting against the counterforce of the far carb, and opening it later than the near carb, resulting in out-of-balace intake.
Even though I can't visually detect the twisting, the out of balance is quite noticable to the ear - and from the engine shaking just as the carbs come off the idle stops.
Just by luck, my throttle cable arm is almost dead-center on my hex-bar. After I have balanced my carbs for idle and just off-idle I can pull on the throttle cable and the RPMs will increase smoothly.
However, if I increase throttle by pushing down on the carb actuating lever on one end of the hex-bar, the RPMs will increase quite roughly because (I've presumed) the hex-bar is twisting against the counterforce of the far carb, and opening it later than the near carb, resulting in out-of-balace intake.
Even though I can't visually detect the twisting, the out of balance is quite noticable to the ear - and from the engine shaking just as the carbs come off the idle stops.
I have also had problems getting my hexbar linkage to open the carbs evenly so I removed the hexbar and installed a center pivot linkage from Scat, It makes a world of difference on how smoothly the engine pulls from idle to full throtle. Jerry