Madass (Don Pender) Carb Linkage Kit

I recently installed one of these kits on my newly refreshed carbs. While assembling carbs, I noted how freely the sleeved slides moved up and down the bores with no effort. After following instructions and adding throttle, I noted right hand carb was sticking at very top of bore. After loosening and tightening all connecting bolts and screws several times, I found that slides did not stick when all was loose, but found that while progessively tightening, either slide might stick, resulting in the right side sticking after all was tightened down. Any suggestions on what to look for or try before I tear the carb assembly all down again? Thanks.
 
jamesp said:
I recently installed one of these kits on my newly refreshed carbs. While assembling carbs, I noted how freely the sleeved slides moved up and down the bores with no effort. After following instructions and adding throttle, I noted right hand carb was sticking at very top of bore. After loosening and tightening all connecting bolts and screws several times, I found that slides did not stick when all was loose, but found that while progessively tightening, either slide might stick, resulting in the right side sticking after all was tightened down. Any suggestions on what to look for or try before I tear the carb assembly all down again? Thanks.
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When you think about it, the stock set up was simply not designed in a way whereby the tolerance of the carbs in terms of the carb tops being perfectly aligned with each other and level and the slide bores being perfectly parallel to each other.

So, you can normally just bolt the carbs on and they’ll be fine.

But with a gantry this is not the case.

I‘d suggest loosening not only the carbs, but also the manifolds, and progressively tightening things, feeling as you go, until you find the ‘sweet spot’.
 
Fast Eddie said:
When you think about it, the stock set up was simply not designed in a way whereby the tolerance of the carbs in terms of the carb tops being perfectly aligned with each other and level and the slide bores being perfectly parallel to each other.

So, you can normally just bolt the carbs on and they’ll be fine.

But with a gantry this is not the case.

I‘d suggest loosening not only the carbs, but also the manifolds, and progressively tightening things, feeling as you go, until you find the ‘sweet spot’.
Click to expand...
Fast Eddie said:
When you think about it, the stock set up was simply not designed in a way whereby the tolerance of the carbs in terms of the carb tops being perfectly aligned with each other and level and the slide bores being perfectly parallel to each other.

So, you can normally just bolt the carbs on and they’ll be fine.

But with a gantry this is not the case.

I‘d suggest loosening not only the carbs, but also the manifolds, and progressively tightening things, feeling as you go, until you find the ‘sweet spot’.
Click to expand...
Yes, that is what I was thinking. I did try loosening the manifold to head bolts, and the carb tops. How tight do you think the manifold to head bolts should be? When I gave them their final twist is when the sticking would start again. Thank you for your response.
 
jamesp said:
Yes, that is what I was thinking. I did try loosening the manifold to head bolts, and the carb tops. How tight do you think the manifold to head bolts should be? When I gave them their final twist is when the sticking would start again. Thank you for your response.
Click to expand...
Are you sure you’re not accidentally allowing the manifold to move slightly with that final twist? I don’t know the torque figure for those manifold bolts but would suggest they‘re RFT. And so long as they’re flat and true, the torque should not effect any alignment etc once set in position IMHO.
 
Fast Eddie said:
Are you sure you’re not accidentally allowing the manifold to move slightly with that final twist? I don’t know the torque figure for those manifold bolts but would suggest they‘re RFT. And so long as they’re flat and true, the torque should not effect any alignment etc once set in position IMHO.
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I did check them for flatness with a straight edge. I will try it again, try to look for that sweet spot. It is one carb that sticks when all is tight. When I was moving things around today, both would stick at times, alternating. I may just trying taking it off and see how they act without it. Are you using one? Thanks.
 
Desmopower said:
Leave your carbs loose on at the head and then snug down the alloy plate on top of both carbs before tightening the carbs to the head.
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I bought one of these kits several years ago. I tried all these things and one or the other carb would still bind.

Don said that it is common for the inlets to be mis-matched so that the carb mounting faces are not exactly flat, which causes mis-alignment of the carbs. Or maybe he said it was the mounting faces on the head....memory fails somewhat.
I wish I'd known that before I bought them....
Anyway, after lots of faffing about, I gave up on the kit and put twin cables back on.

As I said, that was some years ago and the current kits may be different to account for the problem I had.

Good luck sorting yours out.
 
oldschool said:
I bought one of these kits several years ago. I tried all these things and one or the other carb would still bind.

Don said that it is common for the inlets to be mis-matched so that the carb mounting faces are not exactly flat, which causes mis-alignment of the carbs. Or maybe he said it was the mounting faces on the head....memory fails somewhat.
I wish I'd known that before I bought them....
Anyway, after lots of faffing about, I gave up on the kit and put twin cables back on.

As I said, that was some years ago and the current kits may be different to account for the problem I had.

Good luck sorting yours out.
Click to expand...
James,
I have used this kit for a long time with no problems after getting the initial setup done.Took me a while but I think it is a nice unit with just one cable.
Mike
 
jamesp said:
Thank you to all who have offered advice and encouragement. Now that I know this is something that just needs to be sorted out, I can go about it with a different mind set.
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Performed the definition of insanity today by trying various tightening/un-tightening procedures with the same result: no change/never solving the problem. I think the next step will be to remove the gantry and attach the two cable system to see if the carburetor itself is at fault.
 
Alt
jamesp said:
Performed the definition of insanity today by trying various tightening/un-tightening procedures with the same result: no change/never solving the problem. I think the next step will be to remove the gantry and attach the two cable system to see if the carburetor itself is at fault.
Click to expand...
Alternatively you could take the carbs off the manifolds completely, attach them to the gantry and see if the issue persists.
 
cliffa said:
Alt

Alternatively you could take the carbs off the manifolds completely, attach them to the gantry and see if the issue persists.
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James has already noted that the sticking only occurs when the manifold screws have their last tweak to fully tighten them.
 
Dimensional tolerances between carbs, and soft material (esp. when using older carbs) causes carb bodies to warp when being rigidly linked. Inlet manifold tolerances may work against you as well.

A member of this forum ("Time Warp") is a machining wizzard. A couple of years ago he showed how to level carb bodies, carb tops, and manifolds in a fixture, rectifying a troublesome set of carbs and manifolds to work with Don's gantry system.
www.accessnorton.com

TW wrecks a perfectly good Commando etc.

:D The story of skilled labour.
www.accessnorton.com www.accessnorton.com

- Knut
 
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assuming your carb bodies are not warped, loosen all fasteners, snug the gantry to the carbs first, then the carbs to manifolds, then the manifold to head
 
Possible quick and dirty solution, swap the manifolds so current left manifold is on the right and visa versa. If that fails mount only the manifolds to the head, stuff the openings with rags, mark the left and right and draw a long file over the ends of both manifolds simultaneously until both end surfaces are flat and in line with the other. Remove the manifolds and clean leaving the L and R markings in place before replacing on the head.
 
mdt-son said:
A member of this forum ("Time Warp") is a machining wizzard. A couple of years ago he showed how to level carb bodies, carb tops, and manifolds in a fixture, rectifying a troublesome set of carbs and manifolds to work with Don's gantry system.
www.accessnorton.com

TW wrecks a perfectly good Commando etc.

:D The story of skilled labour.
www.accessnorton.com www.accessnorton.com

- Knut
Click to expand...
What I gleaned from that link is that Time Warp is a genius.
 
mdt-son said:
Dimensional tolerances between carbs, and soft material (esp. when using older carbs) causes carb bodies to warp when being rigidly linked. Inlet manifold tolerances may work against you as well.

A member of this forum ("Time Warp") is a machining wizzard. A couple of years ago he showed how to level carb bodies, carb tops, and manifolds in a fixture, rectifying a troublesome set of carbs and manifolds to work with Don's gantry system.
www.accessnorton.com

TW wrecks a perfectly good Commando etc.

:D The story of skilled labour.
www.accessnorton.com www.accessnorton.com

- Knut
Click to expand...
Piece of cake.

Provided you have a mill and the skill !
 
When I installed mine, on new premiers, I had the same issue. no sequence was found where the the rh carb wouldn't stick.
I got it as close as possible - gantry snug, then carb to manifold then manifold to head.
removed gantry and used a flat bar of steel wrapped with wet-dry paper (I think 220 grit) and carefully sanded the tops of the carb bodies untill both were level.
removed carbs, cleaned thoroughly, and bolted back together - now works like it should.
 
Buy this: Amazon product ASIN B07T7ZMGL2
Use it to determine what is not flat and/or not in line. It is possible that the heat insulators between the manifold(s) and head are crushed or partly crushed by over tightening. It is also possible that the O-rings between the carbs and manifold(s) are not in their slots and causing the carbs to be cocked. And, of course it is possible, as others have said, that something is simply not flat. With the glass to check, you are minutes away from knowing rather than guessing!

The glass have quite a few things it helps with - the most important on a Norton is aligning the fork tubes: See Oct 1, 2021 here: https://www.gregmarsh.com/MC/Norton/CustomerCombatBuild.aspx Another is flattening carb bowls, tops, and flanges.
 

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