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Tips
Tips

SU observations from a noob

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What did you spray with?

Try carb cleaner, will make the engine pick up.

It has to be worn throttle shafts.
 
That was carb cleaner. Pick up, no. I can stall it out spraying the front carb.
 
Not in the carb, where the shaft exits. Just a bit is all that is necessary, 1/2 sec shot each side. Use the tube on the can.
 
Did the video play for you? I'm spraying the area where the shaft enters the carb. Not a little shot either, I douse it good. Not sure whether to expect rpm to rise or fall but the fact that I get a drastic change (not so evident on the lousy video's audio track) but it stumbles bad and will probably stall if I kept spraying. So I certainly have leakage....I think. I guess the carb cleaner is plugging the leak and I suddenly have a very rich condition?
 
Carb cleaner burns like crazy, not much is needed. I think what you are doing is flooding the engine.

You really need to have the throttle shafts repaired, Joe does that and I think Hap as well.
 
I guess it doesn't matter exactly what is happening, just that it is obviously happening. Yep, off come the carbs and I'll fit new shafts. I have to do it myself though, this is a low budget hobby for me. Good thing the Weber is waiting to go back on so I can stay on the road.
 
Curto may have oversize shafts in stock. It means reaming the carb body a bit but could be a "quick-n-dirty" fix! Otherwise you'll need to rebush and ream to standard shaft size (replacing THEM as well).
 
I dunno Doc, I once replaced just the shafts without rebushing/oversize and it made a huge improvement. They still were not perfect, but it made the car idle down and I was better able to set the mixture.
 
Hap posted a while ago that the HS2 have the brass shaft riding right on the aluminum carb body, no bushings, the shafts wear quicker than the carb body so most of the time (according to him). New shafts are all you need.
PS I just tried the test again and I couldn't quite stall it but close.
 
H2s can normaly be fixed just by useing the oversize shafts. However, if you want it done correctly, ie fitted, send the carb bodys off to Hap and let him do the deed.
 
Oversized shaft or normal sized shafts? I'll tear them down and see what's what. I wonder if you can get a sleeve type application for those. I'll try to determine how much the body is worn compared to the shafts.
 
After tear down and inspection I decided to try a homemade remedy for fun. I greased up the shaft and put on o-ring between the linkage and carb body, on the outside I greased and covered the end with a coating of liquid electrical tape, dries down to act as a sealed cover. Probably silly but I like to tinker. Don't know how hot things will get, if the o-ring can take it and last a while or not.
 
HS2s are a little different than the other HS series SUs, they are the only ones that don't have a cast in brass bushings in the throttle shaft bores, the shaft rides directly on the aluminum of the carb body. Really this turned out to be a good thing, as the brass throttle shafts are softer than the carb bodies, so 95% of all HS2 don't need Oversized shafted or busihing, they just need a new standard shaft, replace the butterfly with a new solid butterfly while you're at it.
 
It is the shaft that wears not the carb body so.........in almost all cases new oversize shafts solve the prob.
 
My "remedy" appears to be working for now. Able to achieve lower idle and applying pressure to the shaft doesn't alter idle anymore, didn't try a carb cleaner spray test yet (I repainted the heat shield and I hate to ruin the pretty paint). I certainly like the feel and response of the SUs better than the Weber but I don't think it pulls as hard on acceleration. Still, having that Weber hesitation gone sure is nice. I'm tracking some uni-syn auctions. Still a little mystified that mixture adjustment doesn't seem to do much, 6 flats either way on either carb doesn't effect much. Having fun tinkering and learning though.
 
Mine didnt even need the over size shafts The standard run of the mill replacement fit snug as a bug. The body showed no sign of wear, the shafts well that was a nother story. These were HS2's
 
Could see the wear? Mine are shiny where they ride on the body but hard to see the wear, a straight edge along the length of it didn't help much. I'll get some new normal sized shafts when I have an order together. Meanwhile I'll tune and tinker.

BTW
how tight a fit are throttle plates supposed to achieve? I can see a very tiny bit of daylight on an edges here and there
I didn't use sealant on the intake/heatshield/spacer/carb joints, just gasket paper and I fear I missed one as I swear I made 6 but ended up with one left over......
 
If the shafts were worn, you'd see it. The butterflies should be adjusted so you can't see daylight anyplace around the edges looking down the throats with a strong light source from the opposite side, BTW. Sounds as if that's not the issue, tho.

RE: mixture... a "starting setting" is two turns (12 flats) from having the jet flush with the "bridge" of the throat. Usually that puts 'em VERY close. Then the lift pin routine. A ColourTune tool or two can be helpful and a LOT less expense and time than EGA equipment and all it entails. You'd be surprised what a couple flats' turning do to the mix. From all you've posted it sounds like you're really close as-is.
 
I edited my post regarding throttle plates while you were posting....
I played with the fit a little but not much.
I'd imagine slight slop in the plates would really only effect idle, I need to mess around more before I conjecture too much.
I must be pretty close too because it does run very well as is.


Just played some more. With loose linkage, the lowest idle I can get is 900 and it won't go there unless I help it (pressure on the throttle shaft, both throttle screws backed out, both throttle shafts resting on their stops.
I found this note interesting, from a manual
"with the throttle closed there must be clearance between the throttle lever and the carburetter body"
My levers have a stop that touches the body. I left no clearance.
So now I'm wondering if indeed my throttle plates have too much slop, enough leakage to allow idle when fully closed, can I assume that if you backed out the throttle speed screws all the way it should not run at all?
BTW spraying carb cleaner on teh throttle shafts no longer has any effect. I think I'll tear them down again and try to get really decent throttle plate closure.
I really can't get good sync below 1100 still, the rear carb just won't go down far enough, must be leakage yet somewhere.
 
Of course, the throttle lever should not touch the heat sheld either. Hmmm. Is there a bit of room there on yours?
 
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