@@tii throttle linkages and synchronization@@

[BillWilliams]

I have given some thought on how to explain and illustrate the relationship between the (1) fuel control linkage (the linkage that goes from the rotating arm on the Kugelfischer to the intermediate shaft, the shorter one in the photo below) The orange pen is pointing to the tool to pin the pump, discussed later.

and the (2) eccentric shaft (that controls the amount of air) that extends below the throttle body (the orange pen is pointing to it in the photo below) They are connected with the intermediate shaft (the longer one in the vertical position in the top photo).

Orange pen pointing to the intermediate shaft below

All of the linkages discussed hooked together

For this discussion, the intermediate shaft is the shaft that goes between the fitting (with nylon bushing) on the warm-up regulator to the eccentric shaft that extends from the bottom of the throttle body. The eccentric shaft is connected to the intermediate shaft with a pinch connection.

The eccentric shaft from the bottom of the throttle body

The pinch connection comes in two varieties (photo below). One has one M6 bolt to secure it and the other has two M6 bolts to secure it. This pinch connection has a plate on the bottom of it. This plate has a hole in one end and either a grooved stud on the other or it can have two holes. The grooved stud and the two holes secure a return spring. The hole in the end of the plate lines up with a hole on a clip on the intermediate shaft. These two holes are connected with an M6 bolt and nut. This connection keeps the pinch connection from rotating on the intermediate shaft.

Now to the part I find difficult to explain. The tii manual is clear on how to set the relationship between the fuel control linkage and the eccentric shaft in the throttle body. Many of have skipped this step for various reasons. But here is the importance. This adjustment sets the relationship between air and fuel (%CO, AFR, etc) at both idle and running. The %CO/AFR can be fine tuned in the tuna can but it has to be set here first.

To set this relationship, the manual instructs to pin the pump at P1. What we are to do here is to take the BMW tool or one like it, insert it into the P1 slot on the rotating lever on the Kugelfischer through to a round hole in the casing of the pump. This locks the pump (fuel) into the factory set idle position.

P1

P2

P3

P4

With the bolt(s) loose on the pinch connection, we are instructed to push the eccentric in the tuna can against a tool (or drill bit) we have inserted into the hole in the case of the tuna can.

Note the curved section of the eccentric rides against another mechanism in the tuna can (photo above). With the spring connected, the eccentric and this other mechanism work as one unit. The other mechanism is directly connected to the rod on the throttle plate inside the throttle body.

With the spring disconnected, we can see how they are two different mechanisms (photo below).

When you pushed the eccentric to the pin, it moved the throttle plate to the stock idle position.

While we are here, there are two different throttle bodies and what differs is the way to fine tune the air at idle. In either one, there is a small screw on this mechanism that allows you to fine tune (read that turn in 1/16 turns) the %CO at idle. However, unless you make the adjustment at the intermediate shaft, you will not bring it in with this small adjustment device.

After pinning the pump in P1 and pushing the eccentric to the pin, we have now set the fuel and the air to the stock idle setting.

Once you carefully tighten the pinch bolt(s), careful not to over tighten and disfigure the shafts, you have then locked the shaft from the throttle body and the intermediate shaft together thus synchronizing the fuel and the air.

Now you can go back to your regularly scheduled program (tii manual) to fine tune things.

This was a not so good effort at explaining how to set the stock relationship between the fuel and air delivery.

[stone02]

Hi,

clear and understandable. i did

have to read it twice because i

tend to gloss over stuff too often.

i think that the bolts and nuts are M6.

maybe also show the early tuna

can. then move on to the

cold start valve.

stone

[gracer]

Good write up. I push down on the cam to make sure it is engaged in the correct spot on the throttle. You may also reset the CO2 mix for extreme temperatures and altitude. G

[BillWilliams]

Now what do you push down on? What are you calling "the throttle"?

[BillWilliams]

Thanks Chris, I made the change

[bnam]

Bill,

I just went thru this process today. One question on the alignment between the eccentric shaft and the intermediate shaft.

These two should be aligned co-axially -- otherwise there will be binding as they turn. However, the connection between the 2 is not really designed to keep it co-axial -- if the intermediate shaft upper end was a cylindrical instead of a ball it would have been better to ensure coaxial alignment.

I test fitted the intermediate and eccentric shaft and found that they were not quite straight and had to tweak it to get it straight.

Since it needs to be aligned why did they use a ball at the upper end of the intermediate shaft?

Byas

[jgerock]

Bill,

I just went thru this process today. One question on the alignment between the eccentric shaft and the intermediate shaft.

These two should be aligned co-axially -- otherwise there will be binding as they turn. However, the connection between the 2 is not really designed to keep it co-axial -- if the intermediate shaft upper end was a cylindrical instead of a ball it would have been better to ensure coaxial alignment.

I test fitted the intermediate and eccentric shaft and found that they were not quite straight and had to tweak it to get it straight.

Since it needs to be aligned why did they use a ball at the upper end of the intermediate shaft?

Byas

I have wondered about this fitment also, as the coupling is bolted to the intermediate shaft. At first, the coupling wants to sit at an angle because the pin (Ball) isn't sitting inside the coupling correctly (or all the way).

New intermediate shaft with old coupling

New coupling installed January 2011

[oscar94]

Great write up. Any suggestions where I can buy new linkages for my 73tii?

[lilmo]

Great write up. Any suggestions where I can buy new linkages for my 73tii?

BMW dealers, BLUNT, Jack Fahuna, etc.

[oscar94]

Great write up. Any suggestions where I can buy new linkages for my 73tii?

BMW dealers, BLUNT, Jack Fahuna, etc.

Thanks!!

[GRMPer]

Any idea if the eccentric is still available? Mine has 304k on it and there's a noticeable flat spot light/part throttle on the cam. It's physically flatter than it should be due to wear. Makes part throttle very rich.

Per

[bnam]

It is not. Mine had a substantial flat spot. Ended up buying a good used throttle body as these seem to be avail only with the throttle body and not separately.

I've wondered though about repairing the shaft. Either weld on a blob and girdin it down (if this can be done without distorting the shaft), or using something like JB weld. If the linkages are all in good shape -- including the cup bushing at the bottom, the sideways stress on the eccentric should be low and a JB weld should hold. I will try that on my spare.