Throttle rod

Obviously this is a bit that requires not one jot of being fucked with, apart from replacing the rod ends when they wear. I have 2 sets of throttle bodies and they have slightly different lengths. Both rods had been tampered with ,one set by me after having read "something on the net" years ago and the other by the dyno guy. The set that came with the bike have just been overhauled and I changed the rod ends with brass ones. When I set the rod length for these TBs both butterflys were fully closed and the rod length adjusted so that it slipped on its balls without moving the butterflies. The adjusting screw was set around 1/2 of its adjustment. Although I did not remove the arms that the rod connects to, when I measured them their centres appear to be identical. In hindsight I should have asked EFI (the mob that serviced the TBs) to measure them when they had them apart.
I have seen the occasional mention of the rods on forums and some folk relate to geometry and their length but don't elaborate. So are the rods purely a mechanical device linking the TBs, whose length is only governed by the requirement of both butterflys to open simultaneously without running out of adjustment at the screw ? Cheers

Hey Charlie,
I would have thought that so long as the Sacred screw position isn't touched, thats your zero point. Then a T.B. balance would set your throttle plates even at 4000 rpm or where you choose to do it. Then one bleed screw to get even suck at idle ?
I'd be happy doing that until someone called me a Fook-tard
Or am I miss reading this , did they move the Sacred screw setting at overhaul ?
For testing / Rigging purposes, Will these engines run at idle with the Stepper motor blanked off ?

Pete ?

Part of being an Instrument Tech is understanding how links and levers work.

I would say the length of the rod should be exactly the same as the distance between the butterfly shaft centers, this ensures that both levers operate at the same angle throughout the travel.
The rod length adjustment is commonly known as the Linearity adjustment

How did that happen?

Cracked the throttle wide open to get ahead of a cluster of traffic this am. I did have the 2 zip tie trick in place to assure the right hand side wouldn't pop out while riding.

What is the 2 zip tie trick ?

I found that on the right side of throttle body the rod end could drop off due to play in the cup itself. One tiny zip on the butterfly control linkage that then holds another slacken zip tie that carries the rod end on the ball throughout range. Remember this, if the rod end drops off of the ball on eather side there is almost total loss of power...apparently they get worn out quick and develop just enough play to become an issue. I never had a drop off occur on the left side of throttle body so right side was the fix. I'd use a quality zip tie as a temporary fix and/or a preventative for unexpected power loss. Unexpected power loss can kill you on this bike...not that there aren't other things to worry about while riding.

that's alarming!!!

Gootzibird13 wrote:

...apparently they get worn out quick and develop just enough play to become an issue.

This is the first I've ever heard of this happening, and I've been on the Ghetto for a fair while.

I’ve seen it once or twice and I had one of the ball joints on the linkage rod fail on my first set of TB’s.

The reason it kills the motor is because the throttle cables go to the LH throttlebody and the TPS is on the right. When the rod falls off and you crack the throttle the LH cylinder will die as the mixture is incombustible lean and the RH one can’t produce enough power at idle to overcome the extra cylinder pressure in the left pot. It may just keep running but very roughly and slowly or it may just go ‘Phut’ and stall. It’s very disconcerting. When it happened to mine I temporarily fixed it with a rubber band rather than cable ties.

Is what I can't grasp is the ball joints on the shifter are pinned so they can't come off...Why the hell would the linkage on a twin cylinder throttle body not have the same?

 It's distressing that the throttle body ends BOTH cap onto the ball from underneath where gravity wants it to fail naturally....I hope this helps awareness at a minimum. I read it on a forum some years back. Not sure which one gave me the zip tie idea but it could all be resolved by a lockable, proper ball end to begin with.

I don't have to worry about that stuff anymore.


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That type ends have been a problem in many ways, on many mechanical devices. I once had a large one (12mm ball) come apart on a John Deere harvester. It controlled the hydrostatic drive for the transmission. It failed in the intersection of two main roads (four lanes each). I figured out how to nurse it out of the intersection, and got just a preplacement end from another dealer. Deere wanted over $100 for a new control cable, I got the end for $5.

And then there's large trucks. All that air ride trickery, suspension, cab, seats, etc. uses these same style ball ends for the leveling valves. It's annoying when one comes apart in Kansas City, on the interstate, durring rush hour, and your truck bed is now rubbing on the tires, producing lots of smoke.That's when I discoverd the cable tie trick.