Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Can't bring the idling revs down.

Hi Peter, John's 69 Bonnie has the smooth top Concentrics. So no adjuster on top of carb. Just a thin steel bushing that fits in a smooth bore instead of threaded. You can drill the threads & recess.

These cables have shorter inner wire. All 3 cables will have an adjuster built in.

John had much trouble with binding cable. Finally out of frustration he made a 1/4-3/8" spacer to put under rear tank mount. Not that thick, but just enough to allow free cable movement. Has worked well for about 7 years now. Remember this had the smooth top carb top as well.

On bicycle brakes they use the bent "noodle tube" it works really well. I was going to attempt to fit one, but John raised the tank which worked well.

Lubing all 3 cables really helps. Real cable lube is often too thick. Motor oil can be too thick depending on cables & slide springs. I've found real sewing machine oil from the sewing machine shop. Singer, Bernina, brands both work really well. Thin & slippery. I've used 3 in 1 oil. It starts out really then but once the solvent evaporates it thickens to a degree. Sewing machine oil stays the same.

Many ways to sync carbs. I like to get it just close them fully warm motor & set idle rpm & mixture. I equalize slides using drill bit as a feeler gauge. No matter. My point is set the idle first. Then you know where slides will be then you can adjust bottom cables such you have some free play in lower cable housing.

I've found the motor may want one slide a bit higher than the other to get best idle. One side may be richer or leaner. No matter, go for best running.

I make the slides even at about 3/8" opening. Again I use drill bits as feeler gauges. I use the friction screw on twist grip to hold the throttle open. Adjust lower cable adjusters. However, that changes slack throttle closed. So you need to recheck that. As needed give more or less slack in adjusters evenly. Then start over....

The unevenness of idle stops is compensated for by the little bit of cable slack. When you open throttle it will lift on slide first. However you will not & cannot feel this. The motor just starts revving smoothly.

Try not top get frustrated or discouraged. Syncing is a process & simply takes time & practice. Expect several hours in real life. This is "tuning", it just takes time. If your cables are balky it makes the job very challenging.
Don

bodge alert :

"splint" the cable sheathing
into the radius that needs to meet the carb .

Source a piece of Rod about twice the diameter of a coat hanger
and almost as long as the first piece of cable sheathing at the carbburetor .
form it into the small radius needed at the carb end
, like one of those cable end " noodles" , just not hollow .

Nylon-tie this splint to the side of the sheathing
This will supply a solid exoskeleton
to the flexi- sheath-radius
without having to make up new custom cables .

bodge alert accepted.

And not a truly horrible bodge either.

Most work ok without such bodge, though the situation provided by the manufactiurer does invite some questions!

ive done more or lrss the same thing bynslipping a piece of split fuel line over the sheath to reduce the tendency to kink

Just use a bent/formed piece of hydraulic brake tube, cut to length.
If looks bother you, put a piece of heat shrink tube over the assembly.

Works well on the cable adjusters too so they're not banging against the tank and chipping the tank paint. Also a good idea after you're done to do the final adjustment at the throttle after you let it idle and go to left and right fork stops to be sure idle doesn't change.

Steve

Some great suggestions and comments here, many thanks.

Things are generally much better now and I have the bike idling at about 1000 rpm.

Apologies for not giving individual credit for the suggestions (so many came in and many were suggesting similar approaches).

I have carbs with no adjusters on the carbs themselves. The throttle cable exits the carb through a short brass ferrule and the adjusters are about 3" along the cable from here. I have removed all the cable ties that I had previously used and pulled the cables outward when fitting the tank. Once the tank is in place i can poke the cables back underneath and out of the way. After a couple of attempts at this I seem to have got them all running smoothly and pulling equally.

I used the "drill bit" method to check that the slides pull together. Running now sounds smooth at idle.

I am going to leave this alone for now and actually ride the bike for a bit. Well, I will once my new air filter arrives. Managed to lose one on my test ride yesterday! Can't repeat here what I said when I realized this but.....Aaaahhhhh!!!! :-(

Next steps will be to get a remote fuel tank so I can run the bike with the tank off. Buy some new cables (or cable parts) and try to get the adjusters to the front of the tank. I will look at options for cable noodles (bought or made) or some sort of sheath. Plus making sure the cables are kept lubed with a light oil.

Thanks again for all the great advice.

Hi Peter, That’s wonderful news!!
Idling, 950-1000 is good. Sounds like you’re good to go.

Out of curiosity, why would you want to run motor with tank off?
Don

Fair question. Was thinking that adjusting new cables with the tank off will be much easier but actually the adjustment is done without the engine running.
But the real answer is "you can never have enough tools / gadgets!" :-)

Hi Peter, I’m with you 100% on your 2nd answer!!
Don

Bit of an update for anyone who is interested.

Whilst I managed to get the bike to run ok with the original cable setup, I was not particularly happy with the overall reliability or the aesthetics.

I came across a local specialist (Surrey Cycles) that supply things called "Vincent Swept Bends". These go straight into the top of the carb with a "top hat" type fitting and sweep 90 degs. and then have an adjuster on the end. I originally planned to add these to the 2 into 1 setup I had but, after a really helpful chat with Michael at Surrey Cycles) he suggested going twin cables to the twist grip with only one adjuster on each cable (at the swept bend).

Purchased twin cable twist grip, two universal cables, two swept bends and also some lighter carb springs.

Have completed the install and I am really pleased with the results.

I have no affiliation with Surrey Cycles, but Michael is a really knowledgeable chap (BSA's are more his thing but I'll forgive him that) and he knows a lot about AMAL Carbs. Worth a look at his site for carb related bits and pieces.

WOW. Very nice. Looks like that's what they are made for.

Hi Peter, Wow, that is nice!! Thank you for following up.

How does the universal cable work? Meaning, cable housing length, inner wire length, inner wire ends?
Don

Yikes, 25 bucks apiece??????

Well, it does have "Vincent" in the name...

;-)
DJinCA

The cables are 54" long. I cut 13.75" off one outer and 13.5" off the other. I could have made them equal lengthe with hindsight as they ended up so close anyway! The inners ended up at 9.25" and 9" respectively. I have the UK style handle bars which I believe are lower (smaller) than the US type but I think the cables would still work for bigger bars.

The cables come with the carb slider end already attached and three options for the other end. Two are shown below and the ones I used are like the left hand one in the picture but a slightly smaller diameter. I used JB Weld to secure them as I couldn't find any "real" solder (all lead free with a flux core in local shops). I may live to regret that but I did slightly splay the ends of each cable inner and put a good dollop of JB Weld on each before pulling the nipple on, cleaning up and leaving for 24 hours to cure. They survived a good tug to check they were on well before trying to fit them.

The web site shows them as being £20 each but when I spoke to Michael he said they were £10 each (£20 a pair). I will mention that to him, as it had made me think twice about whether they were too expensive. Having fitted them now I would probably say, even at £20, they are worth the money for the tidy looks and (hopefully) reliable settings of the carbs.

https://www.amazon.co.uk/Solder-Mel...mp;s=diy&sr=1-1&ts_id=1939414031


https://www.google.com/search?client=firefox-b-d&q=bakers+soldering+fluid

Links to solder pot and Bakers Soldering fluid, which you should consider strongly, these are just random net images , shop around.

Looking at the recent photos posted it appears you have too many gaskets. The should only be a gasket between the cylinder head and heat spacer. The carb o ring is not supposed to sit against a gasket as per AMAL instructions, just the spacer.

Jonnie, you're correct. Bit of misinformation someone gave me a while back led to that. I have also been informed that in the 1968 parts book for the UK (Standard Edition), there is a plain washer on the carb side, not a rubber / cup washer. Will correct the gaskets when I next need to have the carbs off, as all seems to be airtight at the moment.

True that, Peter.

I’ve learnt the hard way: if it ain’t broke, don’t fix it!

The cable(s) is a nice piece of kit. Looks like it belongs on there.

Cheers,

Steve