Damn spell checker on my phone. Sorry...

Ok so I switched to the new 32mm 3d printed vents that seem to work well but I can't keep the carbs synced. So I have to punt the hex bar and go for another linkage. Suggestions that won't break the bank?

I personally like the Tangering Racing cable setup. Chris knows his stuff, and it's really not much more expensive than most other options. If you have the earlier carbs though without the helper return springs, you might have some issues like I do with the slave carb closing all the way. An easy fix though with a homemade bracket and spring. It's also the cleanest solution and really takes a bunch of crap out of the engine bay. Piece of cake to tune and synch too.


However, the CSP bellcrank setup is well known as a good alternative too - McMark I believe did a big group buy on those awhile back?

Glad you're tracking things down Mike! It'll get there! Can't wait to see pics of the printed venturis!

Wait a minute, first things first. Your last comments were that you'd done it by ear, so have you found a way to set the timing yet? If not then you need to, before you do anything else. If the timing's not right then anything else you do is irrelevant.

Just an observation, there are better linkages, no question, but a lot of people have used hexbar linkages successfully for a long time. Google it and you'll find lots of hints and procedures that people have come up with to get them configured (most important) and keep them adjusted. You can make the hexbar work well. I don't want to suggest that it's not some work, or that you shouldn't spend the money if that's what you want, but I think you still have things left to do to get the thing correctly in tune first.

I did get the timing correct. I have everything else set according to instructions. But when I have both carbs balanced at idle, at 1500 rpm on is at 7 the other is at 10. So I work on the linkage of the one lagging for a while and get it to 7 at 1500. Secure everything. Runs great sitting. Go for a drive and it gets out of balance above idle. Spent 3 hours doing this dance and never could may it work. Granted it may be operator error but I think there is something wrong with the linkage. I could try replacing parts but if it takes that long to figure it out and it needs new parts when it is only a few months old then I lean toward replacing it.

But I am going to try again as you suggested before I spend the money.

pass side idle speed adj screw off the stop?

The CSP Bellcrank is very easy to adjust/stay adjusted and very smooth response but you will still have the hunting idle trouble that Shea mentioned. It is very well built.
But I agree with George that Cable is the way to go IF you are going to spend the money. I have Chris's early setup but did have to have work done on my early webers to make them work.
I have ran both but haven't had a Hex Bar setup but as a few state it wouldn't still be around if it didn't work?

Again, Good Luck!

If the adjustment is changing just because you're driving it then something's not staying where you put it. So if something's moving, what is it? And why? First do you still have some cable slack at full throttle? By that I mean when you floor the pedal are you pulling at the linkage past its stop? On either carb? If you are and you floor it on your test drive you're stretching and "unadjusting" the linkage. Second if something's moving you should be able to find it. Take the linkage drop arms and twist them (softly!) back and forth in different directions. Feel anything moving? Do the same (softly!) with the cable arm and each drop arm, back and forth, anything move? And is the length of your hexbar adjustable? How do the ends sit in the carb mounts? Can you feel any binding? Some have bushings, some bearings, push the bar back and forth and in and out near the carb pivots, feel any movement?

By the way, before the protests start I'm NOT endorsing hex bar linkage, by any means. It has two problems, first the initial setup and second maintaining the setup. The initial setup is logical, you just need to go through it and there are DOZENS of instruction sets on the web, just google. The second, staying in adjustment, is problematic because hex bars have so many different components that are long levers with angles joined with fasteners, so even slight movement anywhere will put them out. That means their adjustment doesn't last as long as it should, but that's typically months or more between adjustments, not minutes. You can do this, tens of thousands of other have, just work your way through it.

EDIT: One other thing, is your hex bar steel or aluminum? If it's aluminum then you can still adjust it, but start saving for something better. And it is a real hex bar, right, not tubular? There were some really cheap tubular bar linkages sold, but I doubt there are any left that haven't been thrown into a lake by now.

and if the xbar is one of the spring loaded (the outboard ends) ones you're fighting that. in my experience, the offset nature of the intakes and if the cable isn't square to the bar attach point you're pulling the the bar sideways right from the gitgo. DID YOU EVER BACK THE SCREW OFF THE STOP? sorry i raised my voice.

Of course mine is one with the springs at the end! It is steel.

I checked at one point to be sure that the cable was not still pulling at WOT but I have not checked recently.

No sure what you mean Kevin by the screw off the stop? Are you talking about the idle speed adjustment?

I just think there are too many moving parts at the wrong angles. For example. Where the adjustable threaded rod goes from the cross bar attaches to the carb throttle linkage, the diameter of the hole in the carb linkage is bigger than the bolt on the end of the rod. Not a big movement but certainly it can change up and down even with the nut tight.

And I have never under stood how the threaded rod with psi it points on both ends is ever suppose to stay exactly the same as the other linkage when they are independent of each other.

yes, the idle speed adj screw on the pass side. take the potential bind, what could be artificial equal flow at idle out. the dr side isas then controls both carbs. after doing the vent swap you prob want to go thru the pre run setup procedure detailed in the cb book. you should be pretty well versed in it.

Have a friend watch the throttle plates as you press the accelerator. Then move the throttle stop under your pedal to accommodate.

The linkage is mechanical. If there are no worn parts it will work if adjusted properly. If adjusted once and then it becomes "un-adjusted" something is at play.

* Adjust the valves
* Set the timing properly (error on the advanced side)
* Fuel pressure must be at 3.5 PSI
* Carbs should be sync'd and tuned with the linkage "off"
* Follow procedures for the idle screw. Not having the engine timed properly can lead to an exaggerated idle setting just to get it to idle and carbs that wander into the progression circuit.
* Drop links should be set at equal lengths. (two 8mm bolts in a vise)
* Linkage mounts should be adjusted to accommodate the equal length length drop links.
* Cable should be adjusted to stop when the plates are at WOT.

Some of this may only apply to the IDA3C type carbs (linkage mount adjustment) but, what is hopefully emerging is a pattern of "everything" has to be right in order to tune a carb properly.

And just in case you missed it:


Go through it all again, the CB book if you have it and Eric's list. NO KIDDING.

No ones made mention of this but I've seen it quite often...check to make sure you installed the aux. vents properly.

Chris pointed out in another thread that they were NOT installed incorrectly. Funny thing is that I have photos with them installed that way right out of the box.

I installed Chris's throttle linkage to address the issue once and for all so I will let everyone know the result soon.

Well I finished the install of Chris Foley's/ Tangerine Racing throttle linkage. I have a completely different car! Runs strong, no hesitation, 2 minutes to sync, and pretty easy to install. I have not driven it very far and I changed a few things in the carb based on Eric's suggestions, but it is clear that this is the best way to run dual carbs.

The time I wasted messing with that hex bar certainly justifies the cost of this package.

Thanks for all the input.