Modern Vespa

So how do i get the throttle tube to snap back closed? I have super crisp snap backs with all my P, PK, and S3 Lammy scooters (both with stock and aftermarket carbs). But with my VB1 (that has a P200 engine and 24/24G carb) it's mostly just a poor man's cruise control. Things i have checked-
-the throttle tube rotates VERY easily and smoothly.
-the carb slide slides VERY easily and smoothly.
-both the inner and outer cables are brand new.
-the inner cable slips through the entire length of the outer cable VERY smoothly...except for the very end of the cable where it makes a sharp bend right at the top of the headset, as it makes a sharp turn into the cable retaining bracket.

Is there anyway around getting smooth snap back with my throttle tube, or am i stuck with it being sticky? And i do realize that the early Vespa throttles didn't snap back , but i was hoping to have mine do it though.

I guess you could isolate it fairly easily by disconnecting at the pulley end and see if it snaps back when pulling it by hand. If the problem is in the pulley/throttle tube then maybe you could fit one of those springs from a P that goes around the tube?

HAS to be the cable binding at that angle.

If you remove the top hat will the ferrule snug into the socket?

Maybe you could try (or fab something similar to) this if not.

https://www.treatland.tv/ProductDetails.asp?ProductCode=throttle-cable-90-cable-guide&utm_source=googleshopping&utm_medium=cse&gclid=CjwKCAjw3ueiBhBmEiwA4BhspCAZFty0Fa8xczvAYTfizwcal-7JCd0rIXM9jYTTqDUZnLJrQDtfihoC81wQAvD_BwE

Put a stiffer spring at the slide?

The ferrule is very tight on the end of the cable. The OD on the ferrule is super loose and sloppy when it's inside (ID) the top hat. It's almost as if i need a top hat that has a much smaller ID. I dunno if they exist or not.

I'm wondering if the inner cable is just rubbing against the top hat, because i can make a much sharper 360 degree bend in my outer cable and the inner cable will easily glide though it.

A P spring won't fit whatsoever.

That's an option, but that spring already is pretty darn springy as is.

If I understand this correctly, maybe a layer of tape on the ferrule to tighten it up in the top hat?

I had this exact same thing happen on the 63 GL. The ferrule was too loose in the top hat, and caused excessive rubbing, making the throttle not return all the way. A thin wrap of tape solved the issue.

CORRECTION - It was the 62 Allstate

Fill the top hat with epoxy and drill to ferrule-snug?

I did exactly the same on my VBA, with an LML 150 engine in it, and I have the same problem ! I tried routing the cable differently, it is better after shortening the throttle cable, minimum distance into the frame, no slack, but it is still a little poor man cruise control

Accept and move on. Ancient technology

I tried something similar to that a couple days ago to get some of the slop out of it. I didn't notice much of a benefit.

I did try something similar a couple days ago and it didn't work for me. I just took a peek at my Allstate, and the split head headset's throttle cable comes in at a much more direct angle than on my VB1.

Then i would feel obligated to remove ALL of the modern technology that i just installed on my ancient VB1.

Other thoughts-
- is to use an oversided outer cable (6mm instead of the 5mm) and still use the standard size inner throttle cable?

- is the throttle cable routing supposed to go underneath the wire harness or above the harness?

Underneath I guess. If you place it over, the cable is not in straight line with the fitting

Anything the inner throttle cable rubs against is going to cause drag.

The top hat is usually the biggest culprit. There needs a straight shot from the pulley thru the bracket, and then from the top hat thru the ferrule.

There also needs to be a straight shot where it exits the outer cable going into the carb. Using the shortest outer cable possible is also a great tip.

The throttle tube has a spring tab welded to it at the grip end that is designed to keep it in the position you set it to. you can grind it off to get better (but not perfect) spring back.

All old models without turn signals holds throttle on the position. I think it because for you can show right turn with hand and not loose speed at the moment.

I nipped that spring tab off last night. It didn't change much in the way of resistance.

Same story on my 50 Special. I removed spring that holds tube, cleaned and greased tube and near nothing was changes. Cable and outer in perfect condition, carb is PHBL 24, sip short pulley.

Next you'll want a brake light switch on the front brake.
I'm all for making things reliable and all but some times you have to realize you are riding an antique that gives prime examples of why we no longer do certain things.

not an easy fix but maybe...

the full length of the tube is in contact and with a heavy grease that is likely much of the drag. if you put the throttle tube in a lathe and turn down the center so it's just in contact for ~2cm at either end that could reduce the drag.

I already installed a working brake light switch on the front brake, so once i get the throttle tube sorted, i'll make sure to remove that switch as well.

That's a pretty good creative idea Patrick. But man, the throttle tube currently spins super easy as is...dare i say even a smoother spin than on any of my P series scooters?

A couple days ago i used super glue and a baking soda mix to glue two different sized feral ferrules to try to take up the sloppy fit inside the top hat. It did take up some of the slack, but not nearly enough. I just took your advice on the epoxy. The JB Weld is currently curing in between the top hat and the ferrule. It's going to be 24 hours until i can see what the results are. If this doesn't work, i have plenty of outer cables, ferrules, and top hats to experiment with for plan D, E, F, and G.

I say aye to this. What's with all the fancy little SIP widgets? The old stuff works fine. With all the old bikes I have (GS160, SS180, V90), the throttles don't "snap back." They are rolled back. This allows the rider to use a hand signal to turn. The PX150E snaps back and it has turn signals. That makes sense.

This is quite hilarious.

Don't laugh too hard, it's a real thing. Not to say that everything is gospel on google, but google search "super glue and baking soda". They react with each other quite nicely and they become an instant hard rock.

Fwiw:

I've solved with treatment similar to Ray8, but additionally JB welding the top hat into the receiving bracket.

For this, I put something under the cable to give it nice curve and good entry angle for the top hat to the bracket so the cable won't foul on that either.

I used acetone to wipe down the bracket and a q-tip to clean its slotted hole - prior to bonding.

Once the epoxy cured, I removed the shim I had under the cable to keep it nicely curved. Net result was the cable not touching anything as it exits the end of the outer or the top hat or the bracket.

I also use the same sip wheel you have.
Mine snaps back nicely.

on my MotoBi clutch I used a 1/4" stainless tube with a teflon tube inside it to make a smooth bend through the frame.

seems like a similar approach could be done here with the right fittings on the ends.

I like this solution a lot … patrick, where are you getting Teflon-lined stainless steel tubing?

bought separately, it's a snug fit when they are straight and then when you put the bend into it (with a tube bender) they lock together. Then trimmed to length after bending and filed the ends square with a jeweler's file guide.

McMaster
https://www.mcmaster.com/89895K723-89895K224/
https://www.mcmaster.com/5239K11/

Aaaaa-SNAP!

It took quite a few hours to get it sorted, but i now have a very aggressive throttle return snap. You can probably hear the snap from 75 meters away! Some of the things i did were-

-i diluted the grease on the inner cable with "Cable Life" spray lube. It thinned down the grease enough create less friction.

-i thinned down the throttle tube grease with Tri-Flow lube.

-JB Welded the outer throttle cable (and ferrule) 100% dead center into the top hat. Thank you Ray for the pro tip!!!!

-slipped a round spacer (about 5/16" diameter) under the throttle cable so that it would support it at an acceptable angle.

Thank you everyone for their input! It was VERY much appreciated!

Gonna try this on the smallie…!

I had semi "ok" return at one point, but swapped the carb, cut the cable and gave up.

On the PX tried 2 new cables, and only got snap back on the second attempt. Seems like a small twist or turn causes friction.

The only times i haven't had a strong snap back with a P/PX was when both the inner and outer cables were corroded or damaged, or if the throttle tube is bent, or if the throttle tube needs a little bit of spray lube. On my P series, i dip my inner cables into motor oil, then grease them up before i install them in the outer cable. I'll also use a grease on my throttle tube as well. After a year or so then the tube quits snapping back as cleanly, then i will give it a few shots of WD40 (or whatever brand of lube i have on hand).

Ah forgot to mention, I was using the Tommaselli quick throttle not the internal throttle with the round wrap around spring.

The Tommaselli is a friction magnet

This is on point.

Great job! Seems you really wanted the throttle tube to return

The whole design of the throttle cable into the headset is pretty poor on the older models.

On the GL and VBB, I worked on them until the carb's own return spring was enough to snap it closed. Getting the cable routing correct was a similar challenge to yours.

Ironically, despite having the strongest spring of all, I think, I've just gotten used to disappointment on the Smallstate.

Nice work keeping up the fight until you got to a solution