Finally found it.

At the end of my long trip last fall I had noticed the bike was not running as smooth as it should. Something seemed a little off but I didn't know what it was. It didn't want to accelerate smoothly from idle and it was not always smooth feeling at certain speeds.
So when I got home I went over the basics and ended up pulling the barrels and replacing the rings and checking everything else thoroughly.
It still ran kind of funny when I got it back together but everthing checked OK. I touched up the VE table a bit and it was running pretty well.
Then 2 weeks ago I put it on the dyno and connected all the monitoring equipment. Something was obviously wrong. The left cylinder was running 150 degrees cooler than the right and the O2 sensor was showing wild swings in the mixture. And it still didn't accelerate smooth.
So for the last couple weeks I have been looking for the problem an hour or so every evening. I looked at all the sensors on the scope and swapped injectors and checked the ignition close but nothing was wrong.
Till tonight when I noticed what seemed like a delay in the throttle sensor response and started digging deeper.
Here is what I found.

[video]https://www.youtube.com/watch?v=jAQVtKKGYVs&feature=youtu.be[/video]

The throttle shaft which was originally one piece was obviously now two pieces. Not exactly what I was expecting....

Two barrel carburetor.......

well you wouldnt expect that, now... why???????

Seems to have occurred early in use so mystery remains why. Something distorting to foul a butterfly on the fly?

hobot said:

Seems to have occurred early in use so mystery remains why. Something distorting to foul a butterfly on the fly?

Click to expand...

The throttle body actually has quite a few miles on it. It was on my bike for a couple years a few years ago but it was mounted to the original curved manifolds then. I just pulled it out and remounted it last spring without the manifolds.

The center of the shaft is relieved for a pin that keeps it from moving sideways. It must be fractured there. I haven't got the screws for the throttle plates out yet to look. The locktite worked good. Jim

Violent vibrations ? :|

I assume then dozens of 1000's miles use but rarre for just useage breaking butterfly shafts but common for wearing pivots till air leaks or sticky swinging. Had us all going there flashing all them hi techy tests at us to end up with ole caveman grooping around diagnosis. Possible intake back slooshing shook the snot out of those big sails &/or cable tension transmitted some rattle fatique. Annoying acceleration for some time eh, what else ya been concealing?

Do most of the corners in your area turn mainly in one direction ?

Isn't it great when you find a mechanical problem you would never have imagined could happen. Now it can be another thing to check when you trouble shoot the next engine malady.
I think all of us have had that aha moment while working on machinery. The things that can and do go wrong never ends. Old timers, as they think they have seen and done it all, get a big smile on their face because they have been outfoxed by the mechanical gremlins yet again. Just think of all the major mechanical and construction failures that wreak havoc on mankind. We will always be but amateurs in the grand scheme of things.

Now Jim,

Had you been running carbs, the sync would've been the first thing you checked!

Isn't it time to mothball that wacky fuely cheater setup and exchange it for some proper 932s and be done with this madness??

She'll run like a dream once you get that fixed.

A fault like tis would have shown up on a pair of vacuum gauges :!:

comnoz said:

hobot said:

Seems to have occurred early in use so mystery remains why. Something distorting to foul a butterfly on the fly?

Click to expand...

The throttle body actually has quite a few miles on it. It was on my bike for a couple years a few years ago but it was mounted to the original curved manifolds then. I just pulled it out and remounted it last spring without the manifolds.

The center of the shaft is relieved for a pin that keeps it from moving sideways. It must be fractured there. I haven't got the screws for the throttle plates out yet to look. The locktite worked good. Jim

Click to expand...

If there is a sharp corner where the relief is located, that is a recipe for a fracture. But I am sure you know that Jim, I'm just putting it out for others to be aware of.

Slick

Only things I can think of is fouling butterfly free swing &/or engine vibes or intake pulses transmitted to shaft long enough the stress riser drilling fatigued out. Hope its easy replacement repair for comoz. Still the rough acceleration part is very curious to me as the more butterflys opened to accelerate the less any assymetry of throttle should matter. But as fine tuned as Jim gets it obviously it did matter which implies he didn't have to crack throttle much for his grin to be pulled back wider. Makes me wonder if a combined 2>1>2 manifold feed by both butterflys might even up thrust better. Flat slides fell out of favor for pivoting butterflys d/t slight uneven stickiness.

Twisting that throttle too hard again!
It is humourous to read the 20/20 hindsight posts that say " I could have found it easily with vacumn gauges etc." Right!

Reminds me of the time I had several experts diagnosing my Rapide twin that had turned into a Comet single about 400 miles from home at a campground. Final expert analysis was that the cams had slipped on their cam wheels and timing chest had to come apart. I was told to arrange a truck to haul the bike home.

Next day after they all left I opened the rear cylinder points gap five thou (Japanese daichi junk replacement points) and roared off with full power. :mrgreen:

Glen

The symptoms were actually very minor. Sometimes undetectable. Once the throttle was twisted beyond 1/4 throttle there were no symptoms at all. There is a fairly large crossover [3/8th in] between the throttle bores.

It wasn't until I set up the monitoring equipment that it became evident that something was not right. The 150 degree difference in EGT between right and left under light throttle confirmed something was going on. Jim

Geeez your pretty smart Jim, I've been looking all over my bike & through the books & I can't even locate the computer controlled double butterfly petrol / air mixture injected intake device.

Bernhard said:

A fault like tis would have shown up on a pair of vacuum gauges :!:

Click to expand...

Yeah, It did show up. Slight differences in the timed map sample between the right and left cylinders. That had me thinking all kinds of bad stuff like cam timing and valve problems -but not a broken throttle shaft...Jim

comnoz said:

The symptoms were actually very minor. Sometimes undetectable. Once the throttle was twisted beyond 1/4 throttle there were no symptoms at all. There is a fairly large crossover [3/8th in] between the throttle bores.

It wasn't until I set up the monitoring equipment that it became evident that something was not right. The 150 degree difference in EGT between right and left under light throttle confirmed something was going on. Jim

Click to expand...

Jim,

The real question your probably pondering is why did it break?

I suspect you are already making a better butterfly shaft

Dennis

Possibly older special blend of metals from North America ,melted down cars and washing machines and rusty bolts made weaker by long sea voyage splashing salt water over bow. Shaken not stirred please.:wink: