Throttle -- double or single cable?

[xwhatsit]

Going through my boxes of 250RS parts looking for an ignition barrel (mine is dying, but no spare), I picked up my spare throttle assembly. Was surprised -- two throttle cables sticking out of it! Went and looked at my own throttle control, and sure enough there's a little hole where the other `pushing' throttle cable goes. Who would've thought!

Anyway, as long as I've had the bike, I've been using the single cable, and it works just fine. Never had it not wanting to return or anything like that. There's perhaps a touch too much free play at idle position, and my one complaint is that it's quite a heavy throttle compared to other bikes I've mounted. It's heavy enough that I can't really operate it with any accuracy with my fingers on the brake. Would a `push' cable improve this, or make it worse? I would've thought it'd make it worse, due to extra friction.

So, should I bother fitting it?

On a related note, I've seen those `short throw' Tomaselli throttles selling for next to nothing on eBay. I never use more than half throttle (I think) around town, so that's OK, but when I need to hoof it, or on the motorway system, I find myself doing `double movements' with my right hand. A short throw throttle would give me more room on that bar (permanently wire headlights on, tiny little clip-on kill switch), improve ergonomics, aesthetics -- Tomaselli throttles are quite pretty, polished aluminium. Worth it?

[xwhatsit]

So the resounding site consensus on this issue is `Leave it alone'

[imdying]

They're not a push cable, bowden style cables can't push. The second cable is to ensure a positive return of the throttle blade should the primary cable crap out. There are a number of things you can do to lighten your throttle pull; lube the cable, lube the throttle tube, decrease the number of turns on the throttle return spring.

[ManDownUnder]

The RF has two cables - one to pull the throttle open, the other to pull it closed (from the opposite direction obviously). I'd fit it personally although I don't ever recall hearing of a "Throttle jammed open causes accident" story on the news...

[xwhatsit]

I meant push in a figurative sense. Maybe figurative is not the right word. If it really was pushing it'd get bunched up inside, wouldn't it?

That's interesting -- so by throttle blade you mean the throttle twist grip? Why is it important to have this return to `idle' if the primary cable breaks; the carb slide will go back idle by itself anyway, won't it?

I might just give the whole thing a jolly good lubing.

Cheers.

[imdying]

Blade, slide, whatever your carb has... remember I live in an injected world now

[bimotabob]

I think harley even call the "push" cable the idle cable in their books.

The bike I own has had a stuck throttle I'm told and spat the previous guy off ruining the original muffler and other bits.
Not sure what caused it as everything is sound.
Although the Yamaha switch gear has the provision for a 2nd cable
Bimota never used it instead use 2 return springs on the Fuel Injection.
I have removed one H/D spring to try to cure the hard throttle.
Now it has a light throttle which doesn't snap back quick giving less engine braking and reving up under gear changes a tad when hot.

Cheers
BB

[imdying]

The bike I own has had a stuck throttle I'm told and spat the previous guy off ruining the original muffler and other bits.

I read that as the original owner binned it and is blaming the bike to cover up his noobiness

[dogsnbikes]

So the resounding site consensus on this issue is `Leave it alone'

Yep you would be right there I have two CB250RS's one with a single and the other with dual cables and really makes no difference to the bikes

bugger to hear about your Barrel though

[xwhatsit]

Yep you would be right there I have two CB250RS's one with a single and the other with dual cables and really makes no difference to the bikes

bugger to hear about your Barrel though

Hahah, yes, I remember you are a man of taste

I won't add the other cable, though. Yep, the ignition barrel seems to have a connection broken inside (instrument panel mountings were broken, so it probably vibrated itself to death), manifesting itself in a non-working tail light and parking light, of all things. Crazy Honda. Anyway, I bypassed it and it's working fine now. Just looking to see if I had a spare in case other connections inside got toasted.

Has anybody used these `short throw' or `quarter turn' throttles? Recommended for a little 250?

[avgas]

2 is always better

[xwhatsit]

2 is always better

Except with cylinders, valves, and chins.

Could somebody please explain to me how the second cable helps return the carb slide to idle if the main cable fails? Surely it would return to idle anyway because of the throttle spring on the carb?

[imdying]

V8s (probably because Holley carbs are such poorly made arse for the most parts) have been the most numerous cases of 'runaway' motors... it is possibly for a motor at full chat to overpower a spring without positive closure... apparently. Never seen it happen myself, but I'm guessing most of the people who have it happen would rather it didn't again

[bungbung]

There are some models of carb that are designed to be used with push/pull cables. Cut from the interweb: All Mikuni smoothbore carburetors are designed for use with a push-pull type throttle assembly. Because of the precision slide fit, slide return is delayed because of high vacuum. Installation of this throttle and cable assembly enables the slides to be pulled shut for instant return to idle.