center pull throttle

[clogsParticipant @clogs]

Hi all,

need to make two centre pull throttle / advance and retard twist grips for an antique motorcycle……no spares available anymore and no copy parts…..

I know I need a real course thread, was thinking Acme…..?….

anyway

the thread would prob be about 20mm long, thats not the problem it's the nut that will bother me as I haven either the knowledge or the equipment to make them myself……any suggestions on anything suitable and where to buy…..

the handle bars are 3mm walled, 25mm o/d, 316 stainless steel………..

any help appreciated…

on another note does anyone else have a problem with the curser….on my apple when going to the next line with the down button….the curser goes to the start of the page……..can we fix this prob…..

over and out……..clogs……….

[clogsParticipant @clogs]

[Phil WhitleyParticipant @philwhitley94135]

Only ever seen one of that type of throttle/AR setups, it used a straight milled slot in the handlebar, and a spiral slot in the twist grip. The cable outer had a stop in the handlebars, and the inner was attached to a brass slider with a peg that poked out through the straight slot, and engaged with the spiral slot in the twist grip. The straight slot in the bars was open ended, and the brass peice with the peg was a sliding fit inside the bars. . Had to be assembled at the twistgrip end first, then the throotle slide fitted to the other end……………Could have been on a BSA Empire Star, but not sure.

Phil

[Bob RodgersonParticipant @bobrodgerson97362]

I am almost certain replicas of this type of twist grip are available. I have seen them at the Stafford International Motorcycle show, which is on this weekend. I believe the smallholder was a Dutchman.

I will try to find out and post on here.

[Bob RodgersonParticipant @bobrodgerson97362]

I just found this on the Britbike forum.

"AMAL straight pull twistgrip, replica items can be obtained from a chap in Holland, who makes them in small batches. His name is Gilbert Bredimus Tel. 00352380236 or email him at bsaonly@hotmail.com he speaks good English and can also supply matching replica AMAL rubber handlebar grips and ferrules to fit the end of the grips."

[Chris Evans 6Participant @chrisevans6]

Also stocked by Cornucopier (Cornucupier ?) Enterprises. A Brit guy now based in Germany. He lists them for the BSA Sloper in both 7/8" and 1" sizes.

You will need to dig deep in the pockets though as they are around £240 a side. I have an old original 1" one here I am trying to swap for a 7/8" version.

You could try also looking at the older Honda Cub step through C70/C90 type of things, they have a similar throttle set up. Adapted to suit your 1" bars the advance would work the opposite way as on 1930s BSA.

[HopperParticipant @hopper]

The cheapest internal cable type throttle/retard parts are probably the aftermarket vintage Harley parts, available on Ebay USA etc. They are for 1" handlebars. Harley used the internal cable set up until about 1970 so they are very common. They are also made as custom parts for guys building Harley choppers who want to hide the cables inside the bars.

The scroll in the outer barell (the twist grip part) is about four inches long and the pitch of the scroll would be about 3 or 4 inches so you won't turn it in a lathe. It seems to me the originals would have been made in two pieces, an inner sleeve with the scroll slot machined in it with a slot drill in a milling machine, using a dividing head geared to the table traverse. Then another piece of tubing has been slid over the slotted one and brazed in position.

The slot in the handlebar is straight. A piece of round bar sits inside the handlebar with a pin that fits in a hole and protrudes far enough to engage with the scroll when the outer barrel is slid on.

[WearyParticipant @weary]

These items were also used on Indian Motocycles until 1952. They are available from many suppliers, who will advise on dimensions etc.

I have found Starklite helpful.

Regards,

Phil

[CHARLES lipscombeParticipant @charleslipscombe16059]

I'm not sure about using twistgrips from American motorcycles – am I right in thinking that these all used a single strand of piano wire not the Bowden cable used on British bikes?

Amal actually made two types of twistgrip, the first was made from 1928 to 1939 and the slot for the slider is in the grip itself – there is no slot in the handlebar. The second type was introduced about 1932 and is much smaller in diameter, more popular than the first type and requires a slot in the handlebar.

The later type was made in several (cheaper) patterns to suit lightweight motorcycles.

BSA seem to have made their own twistgrips and their parts are not interchangeable with Amal..

I don't understand Clog's reference to a short, threaded nut as none of these twistgrips include such a feature. Can Clog please supply more info and possibly a photo?

Chas

[clogsParticipant @clogs]

Hi all,

sorry to be late in replying as I've been away without eMail……heaven forbid…..hahaha…

will now go thru the replies and get back in touch….

thanks one and all….clogs…..

[WearyParticipant @weary]

Hello again.

Charles Lipscombe is correct the standard 'American' throttle & advance/retard system uses a single piano-wire for control .

Anyway, in case it might assist here is Starklite Cycles catalogue for recent models, you want page 99 for the handlebar control groups. As it uses the standard Indian part numbers you can order anywhere of course.

Regards,

Phil

[HopperParticipant @hopper]

Posted by CHARLES lipscombe on 15/10/2016 12:42:28:

I'm not sure about using twistgrips from American motorcycles – am I right in thinking that these all used a single strand of piano wire not the Bowden cable used on British bikes?

…

Yes they did, the piano wire went down the middle of a conventional wound outer cable and operated the carb butterfly lever on a push/pull basis. But you could use it with a Bowden cable with a British type slide carb if you put a slide return spring in the carb.

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