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SU rebuilds

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R

rossco

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Rebuilding my carbs. Maybe. There is slight movement in the throttle shafts where they pass through the bodies of the carbs. Is that critical and if so how much play is acceptable? Should I order new jet bearing kits while I have the carbs on the bench? Am I foolish not to have a carb guy do the work? Who would that be and typically whats the cost of that. Thanks for answers.
 
rossco said:
Rebuilding my carbs. Maybe. There is slight movement in the throttle shafts where they pass through the bodies of the carbs. Is that critical and if so how much play is acceptable? Should I order new jet bearing kits while I have the carbs on the bench? Am I foolish not to have a carb guy do the work? Who would that be and typically whats the cost of that. Thanks for answers.
Click to expand...

Hello,

The throttle shaft should be smooth to rotate and not much play. If there is too much play, air may get in the carburetors and that's not good. I'd replace the throttle shaft bush, which is a telflon sleeve.

If your going to go through the work, I'd install a full rebuild kit.

If you have a local british mechanic, I'd look into his qualifications.
One of the good guys is Joe Curto in NY

Being I'm the first to say hello, others will offer their two or three cents.

Good luck,
Roger
 
Partial answer here. I had play in the throttle shaft. Moss sells a reamer that will bore the holes oversize and an oversize throttle shaft to fit. Easy to do and works perfectly. I understand you can also bore to an oversize, add a bushing and use standard size shaft. Sounds too complicated!
 
I would recommend ordering any Moss parts through British Sports Car Restorations. They are a Moss distributor who gives 16% off Moss' prices.

You can see their web site at www.bscr.com
 
Great answers, y'all. The reamer sounds like the way to go if I don't go to a pro like Joe. BSC for parts is a good suggestion. nevets, I was told that air leakage will make the carbs difficult to balance and adjust. Thanks to everyone for getting back. R
 
If you have HD8 SUs, new Teflon bushings and new standard shafts are the way to go. No reamer required.

If you don't have HD8s, the reamer is rather expensive, and it might be more cost-effective to have someone else do them.
 
nevets said:
Just curious, what are the symptoms of excessive play in the throttle shaft (air leakage).
Thanks
Click to expand...

:savewave:

The carbs may run unavoidably too Lean depending on the amount of shaft wear causing excessive air leakage into the carb.--Keoke
 
Keoke, that's interesting...I'm thinking I may have an intake leak somewhere because although the car accelerates smooth and strong, if I hold it at a constant RPM, say 3k, it runs kinda lumpy. I read something about using propane gas to check for intake leaks...the idea being that if there's a leak, it will pull in the propane and you will hear a difference in the exhaust note. Although, I'd be a little concerned that the sound I'd hear is my garage blowing up.
 
No do not use a highly flammable material. most spray degreaser sprayed around the carbs or manifold will cause the RPM to drop where there is a leak.
 
Found this in an early SU Workshop manual:
When new there is approximately .0025" (.063mm) clearance between the diameter of the spindle and its bearing bores - it must not be closer or distortion from engine heat may cause jamming.
 
Thats why they are called Moss, good for you
 
Often times, most of the wear is concentrated on the brass shafts, and just replacing them (without doing anything to "upset" the bodies/bushings) will restore performance and tunability.
 
HOWDY,
I also have rebuilt my HD8'S recently,one problem took a couple of trys.
idealy, when applying choke,the first motion should engage fast idle.mine did not[first motion engaged jet lever]
upon close observation learned that combination of worn taper pins[8]in shaft's & levers and wear in cam shoe&roller changed
the fast idle geometery. with these repaires made the carbs work properly now.
with respect 59er
 
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