Internal throttle- response

[70 servi]

I replicated the existing (original?) throttle wite with a heavy duty auto choke cable, well greased, grip control cleaned and greased. Carb is nice and snappy without cable, how can I get the same with all assembled?
Thank you responders for your wisdom.

[70 servi]

Wire not wite

[Lowbikemike]

You can't. Internal throttle is not going to return to idle without a HUGE spring on the carb, but then you probably couldn't open the butterfly.

Built in cruise control, you just have to adapt to it.

[70 servi]

I hear ya. But it's really not good. I dont mind no return spring, but when i close the grip I want it to respond faster.

[PanPal]

Sounds like the outer cable has been pinched at some point. A likely area is near the steering stops if it may have been routed incorrectly previously. perhaps the wire you put in is a larger diameter if it worked fairly well before changing. If you throw the bars the other direction, do you have the same result?

[Andygears]

A choke cable was never meant to quickly respond, think clearance between inner and outer cable and tighter bend radii. I have heard of using a guitar string for an inner cable, but never done it myself.

I hope for safety’s sake you have a good kill button while experimenting with different cables, it’s important!

Also, if there is any slop at either mounted end, the response to “back off” will be inconsistent.

Andygears

[Mongrel505558]

I'm trying to get used to an internal throttle myself. I have OEM handlebars and later pull spiral/guts with aftermarket solid wire/cable going to a Bendix carb. You'll never get a really smooth action like you will from an external stranded-cable snap throttle. It IS like cruise-control.

I have tried stranded cable and also instrument wire (piano wire). The Bendix carb has a leather accelerator pump diaphragm that can make the throttle reluctant to close fully without the push action of the solid wire. I have also tried an S&S Super E with a stranded cable and internal throttle, but I had to buy an assortment of cable ferrules and modify the most suitable one to fit into the S&S throttle linkage. The S&S return spring is very strong. Add that to the friction and mechanical resistance of the spiral mechanism and you have a throttle that's a real chore to work.

The most promising solid wire I've come across so far is actual piano wire. I don't remember the gauge, but I have some out in the shed so I can check if anyone wants to know. It's tough as hell - made to last 100 years stretched up to a note and stay in tune, and it doesn't kink. I got a cardboard tube with a bunch of 48" lengths in it. Unfortunately 48" isn't quite long enough. It moves much easier and smoother in the housing than the wire from T-Twin that I have now. I want to find a longer piece of the same piano wire and try that.

There will always be some backlash in the spiral mechanism. When you've grown up riding bikes with external snap throttles the internal throttle is a new experience that takes some getting used to. But that was part of the Harley riding experience up until the 1970's.

[stroker]

mine measured .058 diameter

[Little Stan]

After several years absence from this forum I got a new password this morning so I can share 50 years now of building and riding old HD's plus the one Indian I owned.

Years ago I reworked my badly worn controls of my handle bars, I put the bars on my mill, opened up the worn slots and then made oversize hardware. The best control parts went on the right and the second best went to control the spark which is a little sloppy.

I then went to Ace hard ware and bought whats called a lawn mower throttle control cable! It was super long so I trimmed it to fit and carefully routed the cables. I covered the exposed area with black shrink wrap, lubed up everything with never seize and my throttle is super smooth working the M74b.

A "dead-throttle" will take some getting used to but I have no problem from riding my Pan and then to my 1997 Dyna which has the stock double cable throttle control.

-little stan

[nmaineron]

I'm going that same route but I'm going to try a braided inner core, with a standard throttle cable. Like Little Stan I'm doing the lawnmower cable but it's going to my magneto for advance control.

[pan50head]

To Mongrel's post above. I recently purchased a long roll of music wire at Grangers. It is available in many diameters. https://www.grainger.com/product/GRAING ... lloy-3L554

[70 servi]

Thanks to the responders to my post. I am going to use these suggestions and keep sorting out the bugs with my servi. It is 100% complete, runs, drives, and stops and my goal is to make it drive and stop like when it was new.
Shout out to all the EVO-heads out there. (HD's last stand).
My HD ownership history is: Sprint, Shovel, EVO, and the Flatty Servi.

[flatheadDave]

Thanks to the responders to my post. I am going to use these suggestions and keep sorting out the bugs with my servi. It is 100% complete, runs, drives, and stops and my goal is to make it drive and stop like when it was new.
Shout out to all the EVO-heads out there. (HD's last stand).
My HD ownership history is: Sprint, Shovel, EVO, and the Flatty Servi.

Wait so we are talking about internal throttle on a servi car? What kind of carb do you have ??

[70 servi]

Dave, its a Tillotson MD. When i twist the throttle (rt hand,
Normal direction), it pushes on the carb end. I have ordered a length of .054 music wire, i think it will glide better in the jacket.
Thanks for your input.

[70 servi]

Dave according to "The 45 Performance Book", i should have the Tillotson M or the DC, then it says to get rid of it. My DM looks like a marine carb with the big wheel to adjust main jet.