Throttle cable woes

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hphilbo
Posts: 24
Joined: 26 Oct 2020 17:21
Location: Lancashire

Throttle cable woes

Post by hphilbo »

Having had a throttle cable fail on my 1976 350 sport I ordered a pair of new ones from a well known specialist supplier. They are of Venhill manufacture and are of the dimensions they quote for the bike. However on installation, the throttle slides do not fully close even with the carb top adjusters screwed fully in. The outers are shorter on the new cables, 4 cm on the short cable and 6 cm on the long cable but the run looks ok.
Regarding the old cables, the inner snapped on one and the other has a ‘temporary’ nipple at the twist grip end.
Enough rambling, does anyone have definitive dimensions to get a new pair of cables made up ?
I note that Venhill will do bespoke cables.
Thanks
nickst4
Posts: 185
Joined: 31 Oct 2011 06:55
Location: Diss, Norfolk, UK
Location: Norfolk

Re: Throttle cable woes

Post by nickst4 »

You might do better to make your own. I did that on my Cagiva Alazzurra, eliminating several of the adjusters which allow the cable casings to tilt and alter the synchronisation. You can buy nylon-lined casing and stainless inners as used on pedal cycle gears. For me, it made a world of difference in the stability of carburation, and you don't have to rely on someone else's dodgy specifications. I've also done it on my Ducati ST4 and one of my Gilera NordWests. It's not that difficult!

Nick
MickeyMoto
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Joined: 22 Nov 2008 17:41
Location: Even further oop North

Re: Throttle cable woes

Post by MickeyMoto »

Hi Nick,

Does the cable and outer need any special tool to cut? I have always shied away from this because I think I'll need something very sharp, like a guillotine.

Mike
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Ming
Posts: 798
Joined: 01 Aug 2014 16:32
Location: France
Location: Central France

Re: Throttle cable woes

Post by Ming »

I use a Dremel type multi tool with a cutting disc on the outer sheaths, also on the cable. Not sure how I would fix nipples to a stainless cable, though.
It is also possible to shorten the sheath in cases where the inner is too short if you are careful.
nickst4
Posts: 185
Joined: 31 Oct 2011 06:55
Location: Diss, Norfolk, UK
Location: Norfolk

Re: Throttle cable woes

Post by nickst4 »

A rotary cut-off disc in a Dremel is a good way to cut the very hard metal in cable casings, and also inners too, but tape them before you cut! When I've used stainless inner, I've hard-soldered it to brass nipples successfully, without apparent weakening of the cable. This is only for throttle cables though; I'm not sure I'd trust that for brake/clutch cables. However, I think I used good smooth galvanised steel cable inners for the Gilera throttle, and bought a cheap thermostatic solder-bath to affix new brass nipples. I believe Venhill can provide a full kit for making a good job of bird's-nesting of the cable end, but it's mighty pricey if you only have a couple to do!

Nick
3potjohn
Posts: 1243
Joined: 02 Jun 2007 13:58
Location: Devon

Re: Throttle cable woes

Post by 3potjohn »

I made a birds nesting device by getting a couple of bits of flat steel in a vice then drilling down the middle to give a slot for a cable and then slightly countersinking. Another bit of rod from a door closing device got a similar light countersink.
Put the cable in and whack the rod. Not pretty but effective.Don't forget to put nipple and ferrule on first.
Solder bath is a bit of old radiator pipe held in the vice and then heat it.Tinmans solder is good.
By way of flux as I had some zinc I just dissolved it in drain cleaner (HCL) to make zinc chloride. ( who said the lockdown had been boring)
No points for heating an old nipple only to discover it is made of solder.
John
nickst4
Posts: 185
Joined: 31 Oct 2011 06:55
Location: Diss, Norfolk, UK
Location: Norfolk

Re: Throttle cable woes

Post by nickst4 »

Full marks for improvisation 3pjohn, and thanks for reminding me of the dreaded melting nipples! :shock:

Nick
EVguru
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Joined: 01 Aug 2006 11:13
Location: Luton
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Re: Throttle cable woes

Post by EVguru »

Venhill are the reason I started making my own cables.

They did some years ago post on the forum to ask for feedback on the problems. I sent a detailed reply, but they completely failed to respond in any way.

Even when they're the right length, they use too large an inner diameter for their throttle cables, that doesn't fit the twist grip very well.
Paul Compton
http://www.morini-mania.co.uk
http://www.youtube.com/user/EVguru
70sbikes
Posts: 96
Joined: 13 Nov 2014 11:44
Location: Melbourne Australia

Re: Throttle cable woes

Post by 70sbikes »

Sturmey Archer 3 speed cable (bicycle) is perfect for making throttle cables!
hphilbo
Posts: 24
Joined: 26 Oct 2020 17:21
Location: Lancashire

Re: Throttle cable woes

Post by hphilbo »

Thanks for the responses. Issue ‘resolved’ by removing carb top adjusting screw lock nuts this now allows required slide travel with the new throttle cables. It would appear that the Venhill cable exposed inner cable length before carb nipple, (Quoted as 78mm) is too short for my bike. Removing the lock nuts frees up about 4mm which is enough to allow the slides to close. The cable inners run fine through the original twist grip. Will get some bespoke cables for final repair.
Main learning point : Don’t wear shorts whilst sat on a running Morini !! That heat shield on the rear cylinder exhaust is a killer.
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