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HS6 Linkages and Springs .........


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16 hours ago, Shielob said:

Hello All,

Question when it comes to the linkage back to the throttle pedal. Where the "contorted metal rod" comes out of the passenger compartment it goes through a plastic bush and is then attached to an Actuating Lever, this then joins to the Long Throttle Rod. Does your Actuating Lever (sorry cant find the correct description) sit horizontal to the ground or is it inclined at about 30 degrees?  

My problem is the car sits and idles ok and will accelerate gently but if I open the throttle a bit more enthusiastically the car dies. I am wondering if the arc of taken by the Actuating Lever is opening the butterflies too quickly. A bit like the lobe on a cam which gives a small amount of movement over the first few degrees then accelerates the amount of movement as it rotates.

It may well be distributor timing which may also be influenced by a sudden drop in vacuum but thought I would ask the question and eliminate any complications or easy fixes first.

It is a TR4 with a TR4A linkage as posted by Stuart.

Thanks

Edgar

Thats nothing to do with throttle rod angles, thats tuning.

The rod bracket at the bulkhead sits something like this pictured below, Ignore the rest of the linkage as Im running Dellortos.

Stuart.

 

photo1608.jpg

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  • 1 month later...

Thanks, knowing what it should look like is always helpful. Mine has been brazed and I suspect the angle of the rod has been altered. It did have a PI engine with a really horrible linkage cobbled together.

Edgar

 

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Been out for another look, something is defiantly not as it should be. The Long throttle rod is wound in as far as it will go and the arm is more like 70 deg. 

 

The "Pin" is temporary ! 

TR4 Link.jpg

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On 5/9/2022 at 12:43 PM, stuart said:

Like this.

Stuart.

 

5 - Original SU HS6 operating linkage.JPG

543112_3105953803006_1089104818_32343508_1336163788_n.jpg

546913_3105954163015_1089104818_32343509_32456576_n.jpg

 

I have found that the shouldered bolt which locates through the bellcrank and the throttle support bracket has some play in it on the support bracket when the bellcrank rotates (all new parts from Moss). The thread on the shouldered bolt is 5/16"unf and the hole in the support bracket is 11/32 (0.34in), is that correct or is the shouldered bolt slightly the wrong size? (or the hole in the support bracket too big?) There is enough play to fluctuate the throttle /idle setting and making it difficult to get the carbs set up

Many thanks

David

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Just now, qkingston said:

I have found that the shouldered bolt which locates through the bellcrank and the throttle support bracket has some play in it on the support bracket when the bellcrank rotates (all new parts from Moss). The thread on the shouldered bolt is 5/16"unf and the hole in the support bracket is 11/32 (0.34in), is that correct or is the shouldered bolt slightly the wrong size? (or the hole in the support bracket too big?) There is enough play to fluctuate the throttle /idle setting and making it difficult to get the carbs set up

Many thanks

David

 

carb plate.JPG

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1 minute ago, qkingston said:

 

carb plate.JPG

The shouldered bolt should be tight in the hole with the shoulder hard against the bracket so the slightly larger hole shouldnt make any difference as the fulcrum bracket swivels on the shoulder, are you sure its not the hole in the fulcrum worn?

Stuart.

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20 hours ago, Shielob said:

Been out for another look, something is defiantly not as it should be. The Long throttle rod is wound in as far as it will go and the arm is more like 70 deg. 

 

The "Pin" is temporary ! 

TR4 Link.jpg

Thats about the right angle for SU carbs, mine above is running Dellortos with a different throttle setup, as long as you can get full throttle then its OK. As that rod is threaded both ends make sure that the other end where it joins the fulcrum gives the right amount of movement there, You can always trim the rod thread down.

Stuart.

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14 minutes ago, stuart said:

The shouldered bolt should be tight in the hole with the shoulder hard against the bracket so the slightly larger hole shouldnt make any difference as the fulcrum bracket swivels on the shoulder, are you sure its not the hole in the fulcrum worn?

Stuart.

ok thanks Stuart, the fulcrum is brand new so I would hope not, I get your point about the fulcrum swivelling on the shoulder, I'll try tightening the bolt more to see if that sorts it

David

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  • 3 weeks later...

Ok so my set up is the same as those pictured, however the mechanism is very stiff to operate from the engine bay (the accelerator pedal feels fine), also the throttle doesn't reset to the 'fully off' position when the throttle is operated, the mechanism seems to stick slightly in the last few mm of travel. How tight should the throttle connecting rod be on the carb bodies, how tight should the securing nuts be https://www.moss-europe.co.uk/nut-pivot-auc1424.html?assoc=117608 ? I have some vague recollection that when I bought the SU HS6 linkage conversion set from Moss that there may have been some note re the sizing of the connecting rods, does that ring any bells?

Many thanks 

David

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David on my car, the accelerator linkage is very stiff to operate if you try it back by the accelerator rod. I use the vertical linkage rod between the two carbs, to “blip” them while tuning. As for the two carb connecting rods (throttle and choke), they should move freely. I have the four rod levers tightened on the rods so there is approximately 2mm clearance between the levers and the nuts that hold the rods in place. Make sure those levers are not tight or rubbing against the nuts, as that could bind their operation.

Also check the orientation of the horizontal linkage rod and the bellcrank. The two should be parallel (or nearly) with each other. BTW - on a lot of HS6 schematics (like the one Moss uses), it appears that the horizontal linkage rod connects to the rearmost hole on the bellcrank. That is incorrect. The horizontal rod attaches to the forward bellcrank hole, and the vertical rod connects to the rearmost hole.

Finally verify you are not missing the return spring connected to the accelerator rod lever.

Jim

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On 6/13/2022 at 2:10 PM, Tr4aJim said:

David, here are some pictures of the HS6 carbs on my TR4A in case they help you.

Jim

 

 

CC23E259-6836-4148-82D3-EF94E23A8C9E.jpeg

91DAC163-89B3-47FA-8C53-FF174813ED8F.jpeg

9FD27765-943D-4C01-8EC9-6A4FE88A54DD.jpeg

Jim…
Thread drift
Where did you buy the ribbed heater hose?   We have a TR2 man searching for it.

 

Peter W

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On 6/13/2022 at 3:10 PM, Tr4aJim said:

CC23E259-6836-4148-82D3-EF94E23A8C9E.jpeg

 

Just an idea,

I adjusted this different because I‘m pretty shure the end of the lever is a stop and has to touch the choke bar.

On the photo the stop is the „triangle“ below, touching the bracket, this should have a gap.

And the lever on the pedal shaft is pointing upward on my TR4A for max way per delta deg. on the „pull rod“.

As told above: just a thought, but this works well on my TR4A

ciao, Marco

Edited by Z320
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Marco (as usual) is absolutely correct. When I took the pictures above, the linkages were still loose for carb adjustments. The rod for the throttle has a tab fixed to it. This tab should contact the rod for the choke before the bellcrank contacts the linkage bracket. FYI - I barely had enough adjustment on the horizontal and vertical rods (I don’t know if they’re original) to get even a few mm clearance.

Jim

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Marco, no it works just fine. It just feels stiff if I try to operate the linkages using the lever on the throttle rod. It’s just much easier to operate them using the vertical link. It might be because I use a fairly stiff return spring on the throttle shaft lever, to give a better feel at the throttle pedal.

Jim

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Yes, this is what I mean and what I see,

if you want to get rid of that „problem“, I can explain.

If it doesn’t matter to you it’s ok for me.

Edited by Z320
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20 hours ago, Tr4aJim said:

David on my car, the accelerator linkage is very stiff to operate if you try it back by the accelerator rod. I use the vertical linkage rod between the two carbs, to “blip” them while tuning. As for the two carb connecting rods (throttle and choke), they should move freely. I have the four rod levers tightened on the rods so there is approximately 2mm clearance between the levers and the nuts that hold the rods in place. Make sure those levers are not tight or rubbing against the nuts, as that could bind their operation.

Also check the orientation of the horizontal linkage rod and the bellcrank. The two should be parallel (or nearly) with each other. BTW - on a lot of HS6 schematics (like the one Moss uses), it appears that the horizontal linkage rod connects to the rearmost hole on the bellcrank. That is incorrect. The horizontal rod attaches to the forward bellcrank hole, and the vertical rod connects to the rearmost hole.

Finally verify you are not missing the return spring connected to the accelerator rod lever.

Jim

Thanks for the very helpful comments; my bellcrank and horizontal/vertical rods are connected as described. I disconnected the vertical rod from the throttle connecting bar and the throttle operates smoothly except for the last few mm of travel (back to rest), Jim I take it from your comment above that the carb connecting rod should rotate freely within the securing nuts on the inboard side of each carb; mine doesn't and I think this might have something to do with the fact that when I bought the SU HS6 conversion kit from Moss, they stated that the connecting rods supplied were metric not imperial, I probably didn't appreciate the full implication of that statement. I think I will need to remove the connecting rod and gently reduce the end diameter so that it can rotate freely-make sense?

Many thanks

David

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David, yes those rods must move freely in the mounting nuts. If the rods fit too tight in the nuts, it might be easier to try and ream the nut opening a little at a time until the rods can move freely. An easy way to check if there is binding, is to press down on the throttle levers a bit  (the ones connected to the two throttle springs). There should be a little movement available before the rod levers are engaged, and see the lever and the nut move together, but not the connecting rod.

Jim

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