Trusty Twist Grip Throttle Control

[vhgmcbuddy]

Asked this question last year back on the old forum, but didn’t get a response, so thought I would give it one last try.

My Norton engined Trusty 2-wheeler currently has no throttle control on the handlebars. I believe that originally it would have had a twist grip type control, similar to a motorcycle. Looking at the spare parts list, it shows what looks like a rubber cylinder (the twist grip) and then a long rod which runs down the handlebars to the engine. There is no clue as to how these items are assembled. Has anyone out there ever dismantled their twist grip and maybe shed some light on how it operates (photos would be particularly helpful). How far does the grip rotate between closed and full throttle? Is the grip sprung so that it returns to the closed position when released?

All I currently have to go on is what is shown in the attached picture, which amounts to the rusty end of the handlebar with a slot cut half way through the tube!!

Any clues would be much appreciated.

Thanks,

Sean

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[trusty220]

I apologise for not replying to the original thread, but I obviously didn’t see it at the time.
The twist grip is easy enough to replace; you have the main piece which is the handlebar with the slot in it. The parts that you are missing are the tube that fits around the handlebar to form the handgrip (part no. 2) and the steel plug at the end of the handlebar (part no. 15).
The throttle rod passes through the inside of the handlebar tube and through a close-fitting hole in the end plug (this plug is stepped and free to rotate inside the handlebar). There is a tapped hole in the side of this plug so that you can insert a screw to lock the plug and throttle rod together- this hole is positioned so that you can insert the screw through the semi-circular slot in the handlebar and into the plug. The screw will then act as your throttle limit so that you can only turn the throttle rod through a half-turn (180 degrees).
The handgrip tube will fit over this ( you have to remove the screw first ), then line up all of the holes and insert the screw; the screw’s length is critical because it will wind in until it bottoms out on the throttle rod, and you will find that you’ve probably got too much sticking out of the handgrip. Keep taking a little off the end of the screw until it all fits together nicely, then cover the handgrip tube with some car radiator hose. You can cut a hole in the hose to fit over the screw head and it all works well when it’s done!

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[vhgmcbuddy]

Thanks Geoff, that clears up the throttle control. As you haven’t mentioned whether the twist grip is sprung, I will assume it isn’t.

One last question. I have a few photo’s of your Norton engined Trusty, but they all show the left hand side. Do you have any pictures showing the right hand side, particularly how the throttle rod which runs down the inside of the handlebar tube is connected to the Amal 225 carburetor. My tractor is completely missing the entire throttle control system, so I will be getting new items manufactured. It will make life a lot easier if I have something to base the new bits on.

[trusty220]

The throttle has a sprung action when in use, but this is created by the throttle rod being slightly curved when it comes out of the handlebar tube and follows the straight side of the transmission box. As it turns the curve makes the pressure greater and it will spring back if released. It will also go over-centre if turned a full half-circle.
I’ll have a go at taking some more pictures of the right hand side this weekend for you.

[trusty220]

Some more pictures for you. The ones of the long throttle rod aren’t the best, but you can just make out that there is a dog-leg in the end of the long rod after it comes through the air cowling. There is a loop on the cross-rod that fits closely around this, and another loop on the other end that works the throttle on the carburettor. There is also a slight offset to avoid contact with the magneto.
Good luck with it.

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[vhgmcbuddy]

Thank you once again Geoff. The pictures are very helpful. I wondered what the slots were for in the fan cowling!!

Also noticed the different (i.e. webbed) reduction gear housings on your example. Is that something to do with the longer axles?

Cheers,

Sean

[trusty220]

The webs on the castings are always there on the later type of reduction gears. I think they are slightly different in shape on the early type.

[vhgmcbuddy]

Had a lucky find today. While going through some of the photos I took when stripping the Trusty down, I noticed that there was a stepped boss with a piece of rod attaching it to the top of the crash bar (see photo). This looked remarkably like the missing throttle rod block for the twist grip. Went rummaging through the bits I had removed from the tractor and took the more detailed photo. It’s definitely the throttle rod block, so is one less bit that I need to get manufactured. Couldn’t believe it had been staring me in the face all this time!!!!

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[charlie]

That was a stroke of luck.

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