Carb Linkage Install Questions

Post by **doc** » Thu Jul 27, 2006 3:09 pm

Q1
I'm getting closer on my T4. I'm now mocking up the CB carb linkage. It has become obvious during the mock up that the actual hex bar is too long for my application. I have a DTM installed, so I will be using Jake's spacer blocks to get the hex bar to "stand out" a little. But even if I wasn't using Jake's spacers (which shorten the bar length), I think the bar would be too long.

Is it common to have to cut the bar and drill the holes deeper? This doesn't seem like too big a deal. Any experience here?

Q2
Although my carbs will go on with just a regular gasket, using the phenolic blocks as standoffs makes everything fit much nicer and clearances are much better. Is there any negative associated with using the phenolic blocks that come with the gasket set? Can I use both the regular gasket and the phenolic block for even more room?

doc

500LbGorilla · Post by **500LbGorilla** » Thu Jul 27, 2006 4:01 pm

Q1 - CB makes linkage for different width engines. T4s are narrower.

Q2 - yeah, sure.

Post by **doc** » Fri Jul 28, 2006 6:45 am

Thank you. I see the different length bars on the CB site now. I guess I will set up Jake's stand offs about right, then measure to get the right bar. I'll either cut and drill the longer one I have or order a closer match from CB.

I'm gettin' closer!

doc

MASSIVE TYPE IV · Post by **MASSIVE TYPE IV** » Fri Jul 28, 2006 7:25 am

Doc, I didn't even see this post!

500 pounder set you straight! With the shorter bar you can follow the video for installation step by step, I go over this clearly with the linkage.

Post by **doc** » Fri Jul 28, 2006 4:02 pm

Got it pretty close now. I had to cut about 3" off the bar which was no problem, but redrilling the hole in my home shop was a little tricky. However, looks like I've got it working and getting both carbs to open and close at the same time seems pretty straight forward. Pretty cool - my engines getting close to done!

Jake, I got the bar pretty darn close to the alt and shroud. I could make another plate for one side and get the bar maybe 1/8'' lower/closer to the alternator, but it's as close to the shroud as it can get. I mocked it up with small wood pieces, as you suggested, and came out pretty close after one adjustment. Good method.

Thanks for the help.

doc

Plastermaster · Post by **Plastermaster** » Fri Jul 28, 2006 4:28 pm

Just as a side note for when you have it all installed and are fine tuning all the adjustments on the linkage, I found something interesting, and tested the results a few times to make sure. What I found was that the bolts that connect the heim joints to the lever on the carb are slightly smaller than the holes in the lever. Not much but just enough so there is a little play. That little bit of play has an effect on how well the carb stays in sync as you increase the throttle. At idle, both carbs might be closed the same and in sync with the linkage hooked up, but if it is not perfect and one return spring is more unloaded than the other, at partial throttle the carbs will be out of sync. It is hard to notice but in my case it makes a 15 deg difference in CHT from one side to the other! What the play has to do with is that when you tighten it all down it is easy to push the bolt so that it is not in the same place in the hole on both sides, in effect makeing one lever shorter than the other.

Ron

Post by **doc** » Fri Jul 28, 2006 6:32 pm

Ron,

Thanks. I'll take a note. But I'm way behind that still. CB just sends a drawing on a piece of paper. After you get it figured out how the thing sets up, the "instructions" make more sense

. I spent most of today just marvelling that I got the thing to work and that it works pretty well right from the git go. This is still home shop stuff for me, so I was pretty proud of myself.

I see now that the linkage system is very sensitive to adjustment. Although my set up would "run", it does seem slightly sticky right off the mark and looking closely this afternoon, even after messing around with the little screw bars, I see now that the right carb does not open all the way as quickly as the left carb. Close, but not right. I started experimenting with how the outrigger bars are set on the hex bar when I got called in.

Tomorrow I'll see if I can get it a little closer. Thanks for the comments guys. As I get closer, I know I'll be back for more. Seeing the motor sitting there sorta looking like a whole motor makes me want to try to start the bugger. Pretty soon. Pretty soon......

doc

Plastermaster · Post by **Plastermaster** » Sat Jul 29, 2006 7:53 am

the Dell book has more info on setting up the linkage. I found it tough to get it to work at idle and full throttle, but also my carbs are a little funny in that at idle one screw is turned in a few turns more than the other. Maybe a twisted shaft? Still shouldn't effect the travel though. I think at WOT one carb being a hair out of sinc shouldn't matter much. I cant tell if it does. If it is off at idle and through the progression it is much more noticable. Then there are the guys that taper the edge of the throttle plates to cut the air better at WOT. Might make a difference in the 1/4 mile.

Ron

Post by **doc** » Sat Jul 29, 2006 8:20 am

What you describe seems exactly my situation. The carbs are set a little differently - a few more turns on one of the stops. On the linkage, I can get it synched at either wide open or closed, but not both. If I synch at closed, the 1/2 side is just short of wide open when the 3/4 side is at WOT.

But, I haven't had a chance to play with it, so maybe I will find a way to get it set right. I'm no drag racer. Mine is a 2.0L stocker with fancy paint to drive around town.

I'll get the Dell book. Can you point me to the right version?

It is interesting that you mention "variations" (twisted shaft) in the carbs. Although my carbs are "used" 40 Dells, I know for a fact they ran on Jake's dyno on a very similar motor and did well. So, I hope I have the benefit of experts before me making them good enough to drive. My car has been sitting a long time in the building stage. I'm just trying to get her back to the road.

Thanks for the tip.

doc

500LbGorilla · Post by **500LbGorilla** » Sat Jul 29, 2006 9:09 am

Use an angle finder, Doc, and make sure that the downrods are both totally vertical at rest. Small changes in the geometry here will make a difference.

If they are, already, you can experiment with changing the angle of one of them to compensate for whatever else is going on if you can't find the cause. You might be able to hammer it out that way.

Post by **doc** » Sat Jul 29, 2006 9:28 am

Gorilla,

Do you mean vertical as you look at them from the crank pulley side? (What other way, I guess) This would be adjusted by moving the arms back and forth along the hex bar?

While you answer, I'll try it.

doc

500LbGorilla · Post by **500LbGorilla** » Sat Jul 29, 2006 10:38 am

The arms that mount to the hex bar (the one you cut) can be positioned along the bar any way you want. Position them so that the downrods are vertical. If your linkage is properly set up, it should also be at equal angles as you look at the downrods from the side too. They won't be vertical, most likely, but they should be the same. One linkage downrod should have a spacer to compensate for the carb offsets. You don't want this to be TOO long, but one (left side) should have it.

I have seen non-offset systems used on offset manifolds, and it can be done too, if you watch what you do when you install it. It does make your crossbar not square with the engine.

Post by **doc** » Sat Jul 29, 2006 12:34 pm

Gorilla, your tip was the easy solution. Moving the threaded bars into the vertical position made the whole setup smoother and more positive. The "synch" is pretty close just looking at it.

Pile's tip also helped cause I went round and tightened everything, all the little stuff, and, what do you know, almost everything had a little give in it before tightening.

My set up is such that I can't quite reach the vertical position Gorilla is referring to because my arms are then extended all the way to the ends. But, backing off from the vertical just a little, to get the arms back solidly on the hex bar, everything seems to work fine. BTW, viewed from the side, the angle of the threaded rods is about the same and not too steep. And I have the little 1" extension piece on the 3/4 side. This all is sounding pretty good.

Hats off to the people who did the CB linkage (30 years ago, I guess), but it is a nice piece of engineering. Terrible instructions. But once you start to work with it, the terrible instructions and LOOK AT A PICTURE ON STF of a couple of other similar setups, it's really pretty easy to set up. Even Jake's stand offs, which is just the kind of little fab project that can trip a guy like me up, was not too tough.

Anyway, I'm starting to get excited. Gorilla, I remember when you were working on and finishing your car. Reading your posts at the time, you conveyed the feeling of being close enough to see the end, but still with a mountain of details to attend to. That's where I am.

Thanks, all, for the tips. I will continue to report results.

doc

500LbGorilla · Post by **500LbGorilla** » Sat Jul 29, 2006 3:15 pm

Ironic. Mine looks like this right now.

Maintenance on rods and some head work for better power made me do it. It's like the devil.

Back together in a couple weeks, with any luck.

Post by **doc** » Sun Jul 30, 2006 6:14 am

Nice bike!

doc