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3,000 RPM idle ???

2K views 14 replies 10 participants last post by  rambo 
#1 · (Edited)
Hello,
I've had the carbs off the bike, to clean the pilot jets but also gave the rest a swizz round with the carb cleaner and an air line.
Also put a new throttle cable on and a new RH switchgear housing (the last one for another reason).
I've put it all back together, and started her up. Idle shoots up to 3,000rpm and stays there, with the enricheners on or off. It was fine before, but I've put the throttle stops out a bit just in case.
The carb rubbers are good and I've checked for air leaks as well with a can of easy start.
Carbs are balanced as per Lunmad's youtube video
I can only think that the slides are too "up", but everything's adjusted as much as I can to have them down.

Any idea for a solution? If that is the problem I'm considering shortening the middle adjuster threaded portion.

Position of slides as low as I can get them:



Position of adjusters:





Thanks,
Dan
 
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#3 ·
Hi,

put a new throttle cable on and a new RH switchgear housing
Possibl a too short throttle cable
My first thought too. Or something in the switch cluster.

Any idea for a solution?
Errrm ... if something isn't right when you put it back together, first and obvious place(s) to look at is the thing(s) you changed?

I'm considering shortening the middle adjuster threaded portion.
Why? Did you change that too? If not, what's the logic behind bodging something to 'fix' a problem, the actual cause of which is elsewhere? :confused:

Hth.

Regards,
 
#6 ·
Let's start again

What brand are the cables? From where?
Random ebay jobs are possibly crud

Find a good shop and patronise it
Without you it will go bust

Try not to alter too much at one go

Altering two is only quick if it all goes well ( it never does)
If you add the combined fixing time, the two alterations at a time scheme takes bloody ages
 
#7 ·
The bike was idling & running fine and then you fixed it & now it's not :surprise:?

This happens a lot in here. Like Stuart says, don't bodge something else up to compensate. Don't start thinking it's something else & start tearing that to bits. Go back to what you did & work it out.

How do I know about this ? Well errrrr guess I've done the same once or twice in the past myself :grin2:

In your case I think the other guys have nailed your problem so you should be able to sort it without too much trouble.
 
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#8 ·
Fixed! Throttle twistgrip was jamming up inside the switchgear housing.

Unfortunately it was cheap ebay stuff causing the problem :( Normally I go to LP Williams as my first port of call as they've always supplied me with good kit and know what they're talking about, in my experience anyway. Unfortunately they didn't have the RH switchgear I needed and didn't know when they'd be getting them in. I needed to replace the switchgear as a previous owner (who I can only assume was a rather upset Bruce Banner) had stripped the threads in the back of the switchgear that holds the brake assembly on. If I'm completely honest I wasn't too keen on the idea of the whole brake assembly pinging off the next time I did an emergency stop! :)

So I bought the switchgear from an alternative source. It came with a throttle twistgrip, but I wanted to use the original if I could. No point changing things if you don't have to! I didn't realise the casting inside must have been different, so it wasn't closing properly. I used the twistgrip that came with the switches, and after a bit of fettling to get it to fit the cable end, it's all back together and working! Just have to get another rubber grip now if I can't get the original off.

To answer some of the questions, as you were good enough to take the time to reply:
The throttle was stiff from purchase, I suspected the cables were old, so got a set of Venhills from LP Williams.
The bike idled fine before, but ran rough at very, very slight throttle openings, so that's why the carbs came off. I've cleaned them out with an air hose and carb cleaner, plus shoved a guitar string through the pilot jets to unblock them. Hopefully the bike should run better now.
All the adjusters are on minimum now, which gives an idle very, very slightly lower than I'd like, but that's no problem, I can fix that with the standard adjustment. It was the fact that it was at 3k and I had no room to adjust lower that was the issue. I've got plenty of headroom to go "up" now. :)
Carbs are nicely balanced.
Thanks again everyone!
 
#9 ·
Hi Dan,

Your new switch cluster isn't "cheap Ebay stuff"; there are only two sources of most switch clusters - original Lucas for various upper and lower limbs and Sparx - Phil at LPW would've supplied you exactly the same part. I trust you weren't ripped for more than Sparx's listed £70 + VAT?

The standard twistgrip drum catching in Sparx clusters is a long-known problem; I experienced exactly the same fitting those parts to my T100, but I knew about it already. Amal supplied BSA/Triumph with the same twistgrip for years; it was originally fitted to Gold Stars in the early 1960's, was known as 'semi-quick-action' and is a nominal 1-1/2" o.d. where the throttle cable inner wraps around. For reasons best-known to Sparx, instead of making their cluster casting clear this near-universal twistgrip drum, as Lucas did with the originals, Sparx supply a smaller-diameter twistgrip drum ... :rolleyes:

The throttle was stiff from purchase,
"from purchase" of the bike or just the new switch cluster?

If the latter, be aware that Sparx clusters aren't always well-finished, the handlebar centreline through the cluster might not be the same as that through the twistgrip drum (it wasn't on my T100's), then the fatter part of the twistgrip drum rubs on the walls of the switch cluster. :mad: At the time, the guy I was using to do my machining jobs was a toolmaker, he'd made a jig to finish-machine some Wassell twistgrips I'd bought (something Wassell couldn't be arsed to do :rolleyes:) and he used the same jig to bore the Sparx cluster in line with the twistgrip drum.

No point changing things if you don't have to!
:Huh Then I have to ask why you changed the original switch cluster? "the threads in the back of the switchgear that holds the brake assembly on" are common-or-garden M5; you'd have to hand over the original switch cluster to the biggest bandit in the world to be charged anywhere even remotely near £70 + VAT to have had the four threads helicoiled. Just as a matter of interest, you could consider doing that anyway, then putting either the the original or the new Sparx on Ebay to recoup your outlay ...

Hth.

Regards,
 
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