Throttle Action

Eric Bauer · Sep 1, 2020

Hi all - I just put a new set of Amal Premier carbs on my '73 850 (pictured in Avatar) - the throttle is harder to pull now and not as crisp/smooth. Additionally, the slides make a bit of a scraping noise when engaging. Is that just normal for new carb / spring? The carbs on it were original to the bike and I don't really have a way to know "correct".

Fast Eddie · Sep 1, 2020

Sounds like you might have the springs twisted somehow, or the carb tops fitted backwards.

It could also be the carb clip causing the needle to be miss aligned.

I've heard some say new springs are stiffer, but there should not be any scraping sound, they should open and snap shut nice and cleanly.

You really should at least take the slides out and inspect before damage is caused.

NorCat · Sep 1, 2020

Eric Bauer said:
Hi all - I just put a new set of Amal Premier carbs on my '73 850 (pictured in Avatar) - the throttle is harder to pull now and not as crisp/smooth. Additionally, the slides make a bit of a scraping noise when engaging. Is that just normal for new carb / spring? The carbs on it were original to the bike and I don't really have a way to know "correct".

In my opinion something is not fitted correctly, premiers are smooth, mine are.

Eric Bauer · Sep 1, 2020

Ok - I'll take another look

ELLIS · Sep 1, 2020

Yes i agree as my premiers are super smooth and i did'nt notice any difererance on the stronger springs.

ELLIS

Steves · Sep 1, 2020

One of the more overlooked problems with Amals is over tightening any of the fasteners. Worthwhile experimenting with the carb top BA's and see how the slides seize up when you over tighten. Just don't go crazy with the torque application, it doesn't take much at all!

myron1950 · Sep 1, 2020

When I went to separate cables rather than the junction 2 into 1 I had to replace the carb tops with those that accepted a feruled cable. I had them 180 out of position and as Fast Eddie suggested it caused the un-smooth / scraping sound. When in the correct position - all was good.

Torontonian · Sep 1, 2020

Yes likely the carb. tops. Each has 2 holes for cables , one for choke slide and one for throttle slide lift. You can easily reverse them . Then the cables are not a straight down smooth pull.

Eric Bauer · Sep 2, 2020

I took a look and they aren't reversed - I taped everything off and there is a notch at the back, so while I'm not perfect I was mindful and did confirm. It is reasonably smooth to the final 3/4 but then there is a little bit of friction as it gets up top. And it is more taut than it was, could be old springs were way worn in as well. I'll mess around a bit and see if I can improve. Thank you for all of your thoughts, you are all very helpful as always.

Fast Eddie · Sep 2, 2020

Could simply be old cables and / or kinked inner cables ...

cliffa · Sep 2, 2020

Eric, I know i sound like a broken record, but I can thoroughly recommend the madass140 (Don Pender) single cable gantry.

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Madass140 Single Throttle Cable Amal Kit

im not sure how many of you have bought these but I just installed it last night and it’s beautiful. I can’t tune it yet but I can’t wait to fiddle with it. Despite the instructions being succinct even I managed to get them on just fine. I do have the stop nuts on the cable wrong in the...

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cliffa.

Lineslinger · Sep 3, 2020

Scraping sound in itself is telling you there is hangup/friction where there should not be.

kerinorton · Sep 3, 2020

You need to identify where the scraping is coming from. Get a piece of plastic tube, stick one end in your ear and point the other end close to where you think the sound is coming from. Then you can separate different components to find what is causing the problem. We are all guessing right now.

Eric Bauer · Sep 3, 2020

Thank you - I messed around with it a bit more and it looks like when I put the cables back in it must have gotten kinked or jammed in an odd direction on the frame. I believe this was causing it to stick and perhaps O may have been hearing the scraping sound when it was feeling rough - i know that may sound crazy but it seems fine now that I straightened it out. I had no idea the cables were that sensitive to the way they are run. Thank you all for your help.

Fast Eddie · Sep 3, 2020

Eric Bauer said:
I had no idea the cables were that sensitive to the way they are run. Thank you all for your help.

Cable routing is REALLY important to smooth operating. I’ll sometimes route and re route several times until I’m happy.

It’s also really easy to kink the inner when playing around with carbs etc.

Derek Wilson · Sep 4, 2020

A friend of mine suggested a product to me, called Fluid Film. I bought it to treat some rust that I could not repair easily on my truck, but then have found that it makes a great all around lubricant. I have treated all of the cables on my bike, as well as the twist grip and the cable splitter. It has reduced throttle effort substantially. Requires periodic retreatment, but worth the effort. Works great on the clutch cable.

It sets up into a soft wax, so it has pretty good wash out resistance.

Throttle Action

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