Madass (Don Pender) Carb Linkage Kit

marshg246 · Jul 23, 2023

jamesp said:
I removed the gantry, re-installed my stock two cable system with stock slide springs and all is well now. No more sticking, very positive return.

It's unlikely to be bad, but use the glass to see if the gantry is flat.

Lineslinger · Jul 24, 2023

Seems a shame to ditch the gantry/sync block all because of one anomaly on a fastening point but glad you are back on the seat.
Is there any way for you to attach another Amal to your gantry and see if the problem persists?

jamesp · Jul 24, 2023

marshg246 said:
It's unlikely to be bad, but use the glass to see if the gantry is flat.

It appears to be flat, although I could get a .003” feeler gauge under some sections it if I did not press hard. I put a metal straight edge to it and could not see light when I held it up.

jamesp · Jul 24, 2023

Lineslinger said:
Seems a shame to ditch the gantry/sync block all because of one anomaly on a fastening point but glad you are back on the seat.
Is there any way for you to attach another Amal to your gantry and see if the problem persists?

Thanks for your suggestion, but I don’t have another Amal to test it with.

swooshdave · Jul 24, 2023

jamesp said:
Thanks for your suggestion, but I don’t have another Amal to test it with.

So to be clear the issue isn't technically with the gantry but with out of spec carbs. Would you like to sell the gantry or get new carbs? I might be interested.

jamesp · Jul 24, 2023

swooshdave said:
So to be clear the issue isn't technically with the gantry but with out of spec carbs. Would you like to sell the gantry or get new carbs? I might be interested.

I believe the issue is one of my carbs that goes out of spec when tightened to the gantry. I’m on the fence about selling, will PM you.

swooshdave · Jul 24, 2023

jamesp said:
I believe the issue is one of my carbs that goes out of spec when tightened to the gantry. I’m on the fence about selling, will PM you.

Thanks. I just wanted to clarify for anyone reading this that there isn't anything wrong with the gantry. Sorry it didn't work out for you. As mentioned the carb bodies are so soft (Premiers are obviously better) that that it doesn't take much to tweak them.

batrider · Jul 24, 2023

I can't see how you can reach that conclusion. Carb works fine without the gantry.

jamesp · Jul 24, 2023

batrider said:
I can't see how you can reach that conclusion. Carb works fine without the gantry.

Don Pender says if carbs are not exactly the same height dimensions as each other there could be distortions when tightened up.

swooshdave · Jul 24, 2023

batrider said:
I can't see how you can reach that conclusion. Carb works fine without the gantry.

Which do you think has tighter tolerances, the gantry or 50 year old Amals made from cheese?

jamesp · Jul 24, 2023

swooshdave said:
Which do you think has tighter tolerances, the gantry or 50 year old Amals made from cheese?

Gantry seems to work for many. Don said key element is if both carbs were made at the same time, a matched pair. I believe mine are original to the bike, but I don’t know for sure. I just can’t see buying new carbs at this point in my restoration. And if I did need to buy new carbs, not sure what I would buy.

Tornado · Jul 24, 2023

This might be solved by adding a layer of cork or synthetic cork/rubber gasket between gantry plate and both carb tops, giving it some ability to conform to irregularities in carb heights.

Brooking 850 · Jul 24, 2023

Hi jamesp, I had the same issue when I mounted 32 mm Premiers to my race bike with standard Ali manifolds, to get around the issue I slightly over drilled the holes in the top plate and this sorted the sticking slide problem.
These are now mounted on my road bike with the same manifolds and there is no issue on the bike.
It doesn't take much, just a slight oversize drill will do the trick.
Hope this helps if you decide to try again
Regards Mike

jamesp · Jul 24, 2023

Brooking 850 said:
Hi jamesp, I had the same issue when I mounted 32 mm Premiers to my race bike with standard Ali manifolds, to get around the issue I slightly over drilled the holes in the top plate and this sorted the sticking slide problem.
These are now mounted on my road bike with the same manifolds and there is no issue on the bike.
It doesn't take much, just a slight oversize drill will do the trick.
Hope this helps if you decide to try again
Regards Mike

Hi Mike, I did try that as I noticed early on that the holes for the sticking carburetor were just a little off. I used a small round machinist file to make the holes a little larger. I am reluctant to try it again right now as I need to move on with the bike’s assembly. I spent over a week in my free time trying to figure it out, I now know my carb set up pretty well. I could see where the resistance was by the markings inside the shaft. There is absolutely no resistance now. It could be what you say and I should probably try it again as I hate giving up, I had it very close.

Another thing I noticed after going back to the old setup is that the stock slide springs seem stronger than the Pender springs. My carbs slam shut now, no way are they going to stick.

Brooking 850 · Jul 25, 2023

Hi again jamesp, yes the springs are a little light, although I don't mind that.
On my race bike I had a quick action throttle so light springs weren't an issue.
They are now on my road bike so Ive set and now left.
One of the many pro's is the ability to sync the cabs on the bench before you mount them.

Another con with them is the idle screw as it is so close to the carb body and is a bit of a pain to adjust and I couldn't get the ideal idle as the screw has a coarse thread. Idle was either too slow or too fast.
I ended up putting a lock nut on the top of the idle screw tight down on the top plate, roughly where I needed the idle speed up a bit faster than ideal.
To adjust accurately without turning the screw, just filed a little off the top of the screw until I gained my ideal idle speed.
Hope this helps Regards Mike

Fast Eddie · Jul 25, 2023

Brooking 850 said:
Hi again jamesp, yes the springs are a little light, although I don't mind that.
On my race bike I had a quick action throttle so light springs weren't an issue.
They are now on my road bike so Ive set and now left.
One of the many pro's is the ability to sync the cabs on the bench before you mount them.

Another con with them is the idle screw as it is so close to the carb body and is a bit of a pain to adjust and I couldn't get the ideal idle as the screw has a coarse thread. Idle was either too slow or too fast.
I ended up putting a lock nut on the top of the idle screw tight down on the top plate, roughly where I needed the idle speed up a bit faster than ideal.
To adjust accurately without turning the screw, just filed a little off the top of the screw until I gained my ideal idle speed.
Hope this helps Regards Mike

The twist grip from a 90’s Ducati 916 has a little button that holds the throttle open a ‘crack’.

They’re ideal for bikes that want a faster idle when cold.

swooshdave · Jul 31, 2023

jamesp said:
Another thing I noticed after going back to the old setup is that the stock slide springs seem stronger than the Pender springs. My carbs slam shut now, no way are they going to stick.

The lighter springs are one of the benefits of the gantry. Without the friction of the splitter and the extra cabling you don't need heavy springs.

jamesp · Jul 31, 2023

swooshdave said:
The lighter springs are one of the benefits of the gantry. Without the friction of the splitter and the extra cabling you don't need heavy springs.

Yes, that makes sense, easier on the wrist. If I were to try it again, I would drill the screw holes larger than I did before, and maybe try the heavier springs if slide was still sticking.

jamesp · Nov 2, 2023

Brooking 850 said:
Hi jamesp, I had the same issue when I mounted 32 mm Premiers to my race bike with standard Ali manifolds, to get around the issue I slightly over drilled the holes in the top plate and this sorted the sticking slide problem.
These are now mounted on my road bike with the same manifolds and there is no issue on the bike.
It doesn't take much, just a slight oversize drill will do the trick.
Hope this helps if you decide to try again
Regards Mike

Hi Mike, I did try it again, drilling the four carb. mounting holes 7/32” and now it seems to work with no signs of sticking. Previously I had tried just filing one of the holes to make it larger. I am hoping problem is solved now. Thanks for your suggestion.

arcpoint · Mar 29, 2024

KiwiShane said:
"Stuck" being the operative word ?
I've run 32/34mm MKII Amals on my Commando's for years that worked/preformed very well..just like MK1's...but after the last near miss with the throttle "stuck" on full in wet weather I finally ditched them....my sphincter is very pleased with my decision ☺

Who did your smokey gray metallic paint job?

Madass (Don Pender) Carb Linkage Kit

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