Finally found it.

gregg-k · Dec 17, 2014

Jim,

By chance is the throttle return spring on the opposite end of the spindle from the operating cable? If so, that would load the spindle torsoionally each time you turned the grip. Repeated cycling of this sort may have been the cause of your problem, in addition to the stress-riser caused by the pin you mentioned.

Weber DCOE carbs have their internal return springs at the center of their throttle spindle to minimize this sort of problem. Adding return springs at one end of the throttle spindle (especially in multi carb setups) causes the Weber's spindles to torque, and the butterfiles to go out sync.

..Gregg

comnoz · Dec 17, 2014

gregg-k said:
Jim,

By chance is the throttle return spring on the opposite end of the spindle from the operating cable? If so, that would load the spindle torsoionally each time you turned the grip. Repeated cycling of this sort may have been the cause of your problem, in addition to the stress-riser caused by the pin you mentioned.

Weber DCOE carbs have their internal return springs at the center of their throttle spindle to minimize this sort of problem. Adding return springs at one end of the throttle spindle (especially in multi carb setups) causes the Weber's spindles to torque, and the butterfiles to go out sync.

..Gregg

Actually the throttle return spring and stops are on the cable pull side. The only thing on the other end of the shaft is a TPS which has a very light spring.
I still have not removed the old shaft but I think after looking closely that the shaft is broken starting at one end of the cut for the throttle blade. It was a sharp edged corner and thin at that spot so vibration or air pulses probably cracked it from the inside corner. Jim

Hobot · Dec 17, 2014

Are the parts available to fix it or do ya have to get another throttle body.

comnoz · Dec 17, 2014

hobot said:
Are the parts available to fix it or do ya have to get another throttle body.

I guess since I built it from scratch in the first place the parts are no further away than my mill. A new shaft will be easy.

SquareHead · Dec 17, 2014

Jim and others,

Just want to express my appreciation for all the information and education that is shared through this forum. It is very cool that you all are gracious enough to share what's going on with your Norton's. I am down to just one or two forums, but this is my first one I visit in the morning and regularly throughout the day.

Probably a silly post, but just wanted to drop this in the thread.

Gratefully,

Chris

rvich · Dec 17, 2014

SquareHead said:
Jim and others,

Probably a silly post, but just wanted to drop this in the thread.

Gratefully,

Chris

Well Bro', you are what you is!

Hobot · Dec 17, 2014

Oh ok then good luck getting your piece with a note to avoid stress riser in with prior shop owner work orders. I had loose butterflys w/o shaft issue that had stumbling off idle response but not noticed beyond that. i can vary Peel simple fuel injector pressure if need be by a bent straw sticking out gas cap.

comnoz · Dec 17, 2014

Well now I know, the shaft was broken in the center where the relief for the locating pin was. The locating pin was a piece of drill bit dropped in a hole and held in with a screw. It fit in a 1/8th inch wide slot cut around the center of the shaft.
When I first built the throttle body I just reamed holes for the shaft and the locating pin was needed. A few years ago I had converted the shaft to ball bearings so the pin was no longer needed.
The pin had worn the shaft partway through and then it had cracked from there.

The pictures came out really bad. Here is the shaft after I silver soldered it back together.

Here is all the pieces ready to go back together.

cjandme · Dec 18, 2014

gtsun said:
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.

I'm still laughing from this one gtsun, I was kinda thinkin' the same thing too. Anyway, just another reason I really like this forum, not to mention all the stuff you learn along the way! Thanks for postin' it Jim

lrutt · Dec 18, 2014

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

God I'd hope not........If my Norton ran like my Dream I'd sell it. Under powered under dampened under braked POS.....I love it

dennisgb · Dec 18, 2014

lrutt said:
dennisgb said:

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

Click to expand...

God I'd hope not........If my Norton ran like my Dream I'd sell it. Under powered under dampened under braked POS.....I love it

OMG! Stamped steel frame, crimped pipes, strange squarish look, sold new for like $395...now worth a fortune

worntorn · Dec 18, 2014

Lots of those for sale around here, a few hundred bucks for one in good running shape, which seems like plenty!
Glen

concours · Dec 18, 2014

worntorn said:
Lots of those for sale around here, a few hundred bucks for one in good running shape, which seems like plenty!
Glen

Buy all you can at that price.... :mrgreen:

dennisgb · Dec 18, 2014

concours said:
worntorn said:

Lots of those for sale around here, a few hundred bucks for one in good running shape, which seems like plenty!
Glen

Click to expand...

Buy all you can at that price.... :mrgreen:

+1

Finally found it.

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