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Tue Jun 10, 2014 12:20 pm

So I have owned my FI system for years but I am never really 100% satisfied with the throttle opening sync. When I re-install them and go to set up the linkage travel. It will go from positive close to positive open on one side. Then the other side will go from positive close to 98% open. It doesn not always hit the open stop unless I put my foot into it. The aluminum flex has a little to do with it but I think since the engine is offset and the linkage is longer on one side the arms and heims are traveling at a different rate and a different distance. Even with the arm extender on the left throttle linkage it still travels at a slight angle as apposed to straight. Does everyone feel that this is a bad design or is this something I have to deal with when using flexible aluminum hex-bar linkage? I have always tuned it very close to perfect but it should not be so difficult or have to force anything. What are other peoples experiences?

Tue Jun 10, 2014 2:37 pm

I don't use the CB linkage anymore because of what you have described. I feel the hex bar needs a support bearing in the middle to stop the flexing. All my engines have been converted to the SCAT or CSP push/pull linkage.

Tue Jun 10, 2014 2:43 pm

Dave so which do you like best and are they much qicker to get sync'ed up? I want to hear the snap open and the snap shut exactly at the same time on both and that's not the case with noodly linkage.

Tue Jun 10, 2014 4:35 pm

I have that setup and exactly the issues as you. I sold a kid some parts and the sync link is the next purchase with the proceeds. I had the csp bell crank and it worked well but aesthetically not very pleasing.

Tue Jun 10, 2014 4:39 pm

I like the CSP linkage. It is a lot more expensive, but better quality and an exact fit. The SCAT is much cheaper but it is a universal "one size fits all" kit and some fiddeling and tweaking is required to get them correct, but once set up works good.

Tue Jun 10, 2014 4:46 pm

I swapped the aluminum hex bar for a steel one from John at Aircooled, and 90- some% of my problems went away. I have just set up an old Berg linkage with new rod ends and it is so much nicer in every respect. Biggest problem I've found with the CB hex linkage is that it has no stop for wide open. If the carbs don't hit their own throttle stops at the same time, then you're mashing the pedal, twisting the bar so they both go to WOT. Thing twist and the carbs don't stay in synch. I was able to set the berg so left and right operate exactly the same, and each side has a throttle stop screw. Pete's Sync-link is the next one I try if needed.

Tue Jun 10, 2014 5:13 pm

You can adjust cross bar linkage if one throttle hits WOT before the other and still have them sync'd at idle.

Tue Jun 10, 2014 5:47 pm

The carbs should have stops for WOT. If they don't hit at the same time it's probably the linkages fault................but it's not critical if they are exactly WOT or not. 88degrees might make more power than 90.........who knows.
but if very far off you might consider altering the lengths or angles of the arms to make them more similar.

The correct way is your pedal or linkage should have a positive WOT stop so you don't break cables or bend anything, or use a light touch.
My off-road cars get a positive stop..........you can't use a light touch over some types of terrain :wink:

The CB linkage and filters do work.... but thy sure could use a lot of improvements.

Tue Jun 10, 2014 6:06 pm

I hate the fact that that ball and socket type pivot of the hex bar wears a groove over time leading to slop and inaccuracies in the synch of both carbs.

Tue Jun 10, 2014 6:17 pm

I've used CSP on four engines so far. It feels much tighter than SCAT's, IMO. The finish is much better as well.

If you have the money JKM's bellcrank is top of the line.

Wed Jun 11, 2014 9:40 am

the early empi carbs had a feature they addvertized" thicker throttell arms" well yup they were thick&strong, but they must of went off the orignal print for the hole locations witch were placed for the bend raidi of the thin steel so the new thick ones were off due to more bend on one of the arms so the ratio was off.( holes are there before the arms are bent) I put them in my milling machine & corrected it. the angle of the down rods can also be used for "tuning" the raito some. I dont see the aluminu bar doing/ causing anything. I have the steel hex bar on the shelf,I wont runit. but if you have door/hood springs on your throttell you may hasve another issue......

Wed Jun 11, 2014 10:47 am

I have ran Redline, CB hex, CSP center mount on my baja. They all have the problems you describe to a degree. Berg is clunky and tough to adjust but bullet proof and smooth. I have the Berg on my street car.

I may try sync link next. After dumping hundreds and hundreds in linkage over the years it is hard to stomach another $300 for sync link. . .

Wed Jun 11, 2014 11:20 am

I wasent all that impressed with the sync link type of stuff.but as with everything there are improvements and different strokes for diffrent....pistons.

Wed Jun 11, 2014 11:27 am

So the general consensus is that most, if not all, linkage sucks at sync'ing easily. Ok so there is no reason to run out and get another one only to be frustrated only slightly less. I am going to get the angle of the rods as close to vertical. And I have drilled other holes for the left arm to get the arc length as equal to the right as possible. To get equal power and to keep the balance from left to right the throttles should start and stop at the same point but also accelerate at the same rate. I know I can get it "Close enough" but wanted to rant a little and see what others thought on this across the choice of products. If I discover any new assembly methods or parts mods that make this task more palatable I will add them to this thread. I may just fabricate my own. since we all know too well "You need to do it yourself".

Wed Jun 11, 2014 12:10 pm

mark tucker wrote: I wasent all that impressed with the sync link type of stuff.but as with everything there are improvements and different strokes for diffrent....pistons.

Setting the $300 aside, what did you not like about Pete's design? Or, you liked it but just weren't impressed by it?

Wed Jun 11, 2014 12:39 pm

Here is an idea for extending the left side arm to achieve equal geometry with straight manifolds. Offset manifolds make hexbar easier to work with. With straight manifolds the offset has to be made up for with an extension. This is just a very cool looking version I saved the pic of.

Wed Jun 11, 2014 12:51 pm

Single TB=no linkage. Just sayin'. 8)

Wed Jun 11, 2014 12:59 pm

miniman82 wrote: Single TB=no linkage. Just sayin'. 8)

I have dual 48's and 8 injectors. I think a single would be a great concept but velocity would suffer.

Wed Jun 11, 2014 1:58 pm

you may find you need to angle one ,ore than the other to get where you want to be. "T" sloting with "T" nuts would be another option if there was room for it.
as for the synclink or whatever it's called now I dont know if it was petes or not, it was a prototype made hear in northwest fl years back(5-8 I think,dont rember when exzactly) & the others Ive seen on a few cars. the guy that had one of the prototype's changed his a little(for the better I think) so the cables pulled seperatly off a common cable(like bike stuff), not one carb being a slave. I had heard it all went up north to be built after some buthead got in the middle or something like that,but thats hearsay so I dont know the reason or if the guy down hear just did the prototype & turned it all over .it all looked neet and very well machined but just wasent for me.the price tag has nothing to do with it. I do seem to remember that jake was involved someway with it. Im sure it works just fine and looks good too and has the AWE factor. kinda like the guy with the google glasses last night when we were shooten pool,he never shut up for more than 5~7 sec & just kept babbling.

Wed Jun 11, 2014 3:13 pm

JayCee has a new push/pull style linkage for race and or street. You should call Jack and ask him about it. http://jayceevw.com/new_products