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Need help with throttle linkage. What am I missing?

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NOHOME P P
O, Ontario, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
When the car came to me, there was a bit of jazz going on with the throttle linkage...but it did work.

Trying to revert to the factory setting, I came across the following diagram:



At first, I thought it solved my problem as it showed that the bellcrank that is bolted to the manifold was in the wrong configuration with the lever at the bottom rather than the top.

But then , I worked the motion from pedal to throttle and realized that this cant work; the throttle lever needs to be pushed up and this will pull down.




The fallback is to just go with the jazz ensemble that was in place when the car arrived, but I prefer to have things done right. This thing had to have worked from the factory, what am I missing?



Edited 1 time(s). Last edit at 2017-10-07 03:28 PM by NOHOME.

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Craig Clifton Avatar
Martinez, Ca, USA   USA
That diagram is incorrect. If you flip the lever at the pedal pivot shaft 180 degrees it will be correct.

NOHOME P P
O, Ontario, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
Craig:

Once again, I have to thank you for your expertise. It did not look like it would clear if I faced the pedal lever forward, but I am going to try tomorrow just because OCD with this stuff.

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simon1966 Avatar
simon1966 Silver Member Simon Griffin
.Madison County, Illinois, USA   USA
1953 MG TD
1954 Austin-Healey 100 "BEV"
1977 MG MGB
I am not sure if this will help you or not. My car is a Right Hand Drive. Here is the linkage assembled on the bench by my restorer.


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NOHOME P P
O, Ontario, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
Thanks Simon.
Going to take a shot at it again today.
I actually have the throttle working now, but it involves running the return spring back to the firewall; I am trying to undo some of the creative engineering that was done previously, so I am not comfortable leaving good enough alone.

Pete

simon1966 Avatar
simon1966 Silver Member Simon Griffin
.Madison County, Illinois, USA   USA
1953 MG TD
1954 Austin-Healey 100 "BEV"
1977 MG MGB
Pete, I know what you mean about PO;s. My car had been converted to hydraulic clutch back in the 60's using brake parts. It had the 4 speed BN2 box put in at that time as well. I decided to go back to the correct mechanical linkage for the clutch but kept the 4 speed. My restoration started out as a home resto. I realized very quickly that I did not posses the skill set to do it properly. My skills lie in other places and I am blessed to have been able to fund the restoration. Seeing the enormity of the work that has been done on my car makes me realize even more that there is no way I would have ever completed it.

NOHOME P P
O, Ontario, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
It is funny. Using the components in the picture, there is no configuration that will allow the throttle to work properly.




As shown, if I reverse the lever on the throttle pedal, the link from the firewall to the header bell-crank will hit the rear float-bowl.

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Craig Clifton Avatar
Martinez, Ca, USA   USA
Pete, I will try to get some pics of mine for you. It matches that diagram exactly EXCEPT for the lever at the pedal end. In the meantime could you measure the lengths of the two linkage rods?

Edit: measure the 3 linkage rods , if possible. Also, pics of the orientation of the bell crank on exhaust manifold and on the top of the
driver's foot box would help.



Edited 1 time(s). Last edit at 2017-10-10 12:44 PM by Craig Clifton.

NOHOME P P
O, Ontario, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
Craig:

Will do.

Cant decide if I am more fascinated or frustrated by this whole linkage thing.

I found a workaround where the middle bell-crank 9Manifold) is rotated so that the middle rod is angled downward, but it involves reversing the return spring pull by making an attachment point on the firewall.

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Craig Clifton Avatar
Martinez, Ca, USA   USA
I am suspecting that one of the rod lengths may be wrong or that the lever on the carb throttle shaft is oriented incorrectly. While the horizontal rod on mine passes close to the bottom of the rear float bowl, neither it, nor the bell crank, make contact.

NOHOME P P
O, Ontario, Canada   CAN
1967 MG MGB GT "Maggie (GT From Hell)"
If these cars were easy they would be no fun. It could be a case of adjustment or rod lengths.

I just finally figured out why there are two wires on the negative coil terminal.

The second wire ( they are all white on this car) FEEDS power to the green accessories circuits.

PAN Avatar
PAN Alwyn Keepence
Ipswich, Queensland, Australia   AUS
G'day "Nohome",
I have seen the 100 throttle linkage assembled in many 'creative' ways so I am not surprised at your confusion. The right hand steer set up is a little more complicated so let's ignore it for the moment.
I believe the first drawing that you included is correct. The shaft that rotates when the pedal is depressed (item 2) turns in a clockwise direction, pulling the first rod downward. The horizontal rod is thus pulled to the right of the diagram, towards the back of the car. The short rod that is attached to the throttle shaft lever on the at the carburettors is then pushed upwards, opening the throttle.
Your red arrows, in my opinion show the throttle closing.

Craig Clifton Avatar
Martinez, Ca, USA   USA
Alwyn, the lever at the pedal is absolutely shown incorrectly in the drawing. Please excuse my poor image edit, but this is the correct orientation. The lever on the pedal shaft goes forward and is connected to the rear facing arm of the upper bell crank. In the process, the vertical link crosses a centerline between the pedal pivot and upper bell crank pivot. My throttle linkage has never been altered, well at least not since 1963......


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Craig Clifton Avatar
Martinez, Ca, USA   USA
Here are a couple pics. Ignore the 35+ years of dirt and grime.

The first shows the linkage at the manifold and carbs. The forward bell crank comes very close to the steering column when in the "closed" position. The lever on the front carb should be angle downward a bit.

The second pic shows the bell crank at the top of the foot box. At rest, the brass connector is just clear of the top of the foot box. If you look real close, you can see how the vertical linkage rod goes forward to the pedal lever.


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PAN Avatar
PAN Alwyn Keepence
Ipswich, Queensland, Australia   AUS
Thanks Craig, I can see that now.
What threw me was the direction of the view. It is from the left not the right. In that case the pedal shaft rotates anti-clockwise to open the throttle.

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