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TR4/4A SU HS6 throttle spindle size

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Djoslyn

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I had inherited this car from my uncle around 10 years ago and I know nothing about its history. I'm finally in a place where I can start to work on some of the minor issues it has so on to my question.

My carbs are leaking around the butterfly spindle. I'm trying to determine if they have been rebuilt before or not and if they have stock spindles or oversized spindles. I can't seem to find the stock spindle diameter on these carbs.

The ones currently installed are measuring 0.312in or 5/16.

None of the places to order from specify the diameter other than stock or 0.010 oversized...

Thanks in advance!
 
I have a 1960 TR3A with H6 SU carbs. I believe them to be original. I measured non wear areas on both carbs and they both measure .310" You could contact Joe Curto. He has great videos and a good website.
 
I did come across his videos earlier today but he doesn't have any specifically up on the HS type carbs. He does mention in the H type bushing installation video about reaming the new bushings to 0.313in, so if the H type carbs use the same diameter shaft as the HS carbs then I'm guessing mine are the stock diameter.

If no one else responds to this then I may contact him directly for the info.
 
I have a pair of new shafts and they measure 0.310"
Joe does a great job rebuilding the carbs. They come back like new ones.

David
 
I took some more careful measurements and the shafts on mine are also 0.310. Also after some more cleaning and having a closer look the bodies have been sleeved already at some point in the past. It looks like a re-sleeving is probably going to be necessary to get the carbs back into shape.

Thanks for the help everyone.
 
I always test the shaft to bushing/carb fit by putting the unworn portion of the shaft into the carb and ‘feeling’ if it’s loose or not. I use this method on HS2s, 4s, 6s and 8s and it works well.
Rut
 
I may try that first when I decide to pull the carbs and take them apart. There is an almost an imperceptible amount of play in the shaft rights now, which I'm sure is way too much.

I'm thinking about just buying the reaming kit Joe Curto sells and just doing it anyways. :smile:
 
I bought the piloted reamer for .010 oversized shafts about 8 years ago along with the reamer for Spridget kingpin bushings and sold both a few years ago because I never rebuilt a carb that needed it. The kingpin reamer was very expensive, never used, and World Wide reams bushings for free when you buy their parts. I’m not saying that you won’t ever run into a carb that needs reaming, but after a few dozen SU rebuilds I’ve yet to find one.
Rut
 
Good to know. I'm not surprised to find out that he sells the reamer kit for more than double the price he charges to do the bushing/shaft install service. I'll definitely make sure that I really need new bushings before I go down that path.

Would you recommend starting off with one of the available master carb rebuild kits? or should I just worry about replacing the shafts and gaskets for the time being. The car runs great other than an inconsistent idle due to the vacuum leak caused by the worn shafts and possibly bushings..
 
Ten years is long enough to completely ruin the seals in the carbs. The cork will probably fall out in crumbs. Definitely rebuild that first. Then when it's running well you can try some grease on the spindles as a temporary fix to see it that is even a problem.
 
I was wondering about the possibility of putting grease on the spindle to temporarily "seal" the vacuum leak. I"ll get a full gasket set, replace the old ones, do some testing and go from there after I see what the results are.
 
I have rebuilt several of the HS6 carbs. On those I found that the spindles seemed to take the wear as opposed to the carb body. I used a rebuild kit from TRF that worked well. Yes the spindles are 5/16". If you remove the spindles you should see the wear on them .
 
That was my understanding as well. But it appears that these have already had brass sleeves put in them at some point in the past which has me worried that there could be wear on them as well as the spindle.
 
AFIK, all HS6 carbs left the factory with brass bushings. The Moss TR2-4A catalog used to have a good article on re-bushing SU carbs. I think it mentioned .002"-.003" clearance (which seems like a lot) with newly installed bushings&throttle shafts.
Berry
 
Djoslyn said:
Good to know. I'm not surprised to find out that he sells the reamer kit for more than double the price he charges to do the bushing/shaft install service. I'll definitely make sure that I really need new bushings before I go down that path.

Would you recommend starting off with one of the available master carb rebuild kits? or should I just worry about replacing the shafts and gaskets for the time being. The car runs great other than an inconsistent idle due to the vacuum leak caused by the worn shafts and possibly bushings..
Click to expand...

I’m no expert by any means and my personal approach has always been to buy the rebuild kit and install the throttle shafts first to get a feel for any possible carb body wear. You’ll need the kits anyway for the rebuild and if the bushings are worn to the point of causing a high idle address it with new bushings (my preference) or the oversized shaft.
Rut
 
Rut said:
I’m no expert by any means and my personal approach has always been to buy the rebuild kit and install the throttle shafts first to get a feel for any possible carb body wear. You’ll need the kits anyway for the rebuild and if the bushings are worn to the point of causing a high idle address it with new bushings (my preference) or the oversized shaft.
Rut
Click to expand...

That is what I'm planning on doing at this point. Thanks for all the help!
 
If the spindles are worn you will see it when they are removed. If they are not worn then one would assume the bushings.
 
So I rebuilt the carbs with the SU master rebuild kit. The old spindles were definitely worn but the front carb bushings are worn enough that it still has play and leaks at idle with the new spindles installed. Looks like I'm sending the carb bodies to Joe Curto for new bushings.
 
titanic said:
AFIK, all HS6 carbs left the factory with brass bushings. The Moss TR2-4A catalog used to have a good article on re-bushing SU carbs. I think it mentioned .002"-.003" clearance (which seems like a lot) with newly installed bushings&throttle shafts.
Berry
Click to expand...
I bought a new set of HS6 carbs from Rimmer Brothers and I thought that the throttle shafts "felt" too loose but when I measured the play with a dial indicator it was exactly between .002 and .003. They have brass bushings.
 
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