View Full Version : How to check for leaks at throttle shafts? (dual HS2's)

11-13-2003, 02:32 AM
I had read that there was something you could apply to them to temporarily fix a leak (at least long enough to note any change).

I still have that flat spot at over 4k that gets better with full choke, so I thought I'd give it a shot before throwing the ZS back on. I miss driving my car and I'm sick of tinkering!

Mark Jones
11-13-2003, 08:37 AM
With the car running you can spray ether around the throttle shafts. If the speed of the engine increases you have an air leak.

11-13-2003, 08:41 AM
....or instead of "starting fluid", you can spray WD-40 near the bushings and the engine will slow down. Use a "straw nozzle". It's less fun, but safer.

11-13-2003, 12:49 PM
A propane blowtorch [unlit images/icons/wink.gif ] will also do the job and may be easy to control than an ether spray. You can pinpoint the leak area with the tip and the flow turned on low.

11-13-2003, 03:39 PM
Hello CC,
at 4,000 rpm and I assume full open throttle, a little leak from the spindles is irrelevant. It will affect your idle and not much more.
If pulling the choke helps it is too weak at that point.
What car are you running HS 2's on, I would think that they are too small for any Triumph?

Alec graemlins/cheers.gif

Trevor Triumph
11-13-2003, 03:59 PM
I thought S.U.s were standard on early Spitfires. Mine has the H2, one and 1/4 inches. I think the shafts could be replaced on mine but I understand it is an intense machining job. So far though I get about thirty miles per gallon on the highway and the car does run well enough. If it ain't broke... T.T.

11-13-2003, 06:58 PM
Trevor, nine tomes out of ten, it's only the shafts that are worn, not the carb body. It is no big deal at all to replace then.
If you have to have the oversized shafts fitted due to wear in the shaft bores, thats a bit more difficult. Someone out there, perhaps Moss, sells a piloted reamer, to ream the body for the oversized shafts, or you could just send them to Joe Curto, and let him do it.
The 1150's, and the 1300's ran HS2's. Here in the States, the 1500 got a single 1 1/2" Stromberg, while the Euro versions had twin HS4's.

11-13-2003, 08:15 PM
I think Alec is correct. A leaky throttle shaft wouldn't really create a flat spot at 4000.
Is your fuel filter clogged, or do you have a weak fuel pump?
Are your floats set too low?
Do you have a sticking piston in one carb? (pull the air filters and rev the engine while looking at the carb-pistons)
Do you have the jets backed out the correct number of flats?
Does one carb have a partly clogged main jet or float bowl? You may have one lean carb. While the air filters are off, have someone hold the engine at about 2000....put your hand partly over each carb intake (one-at-a-time) and see if they both react the same way.

By the way, be careful with any flammable stuff near a running engine. DON'T do this:


[ 11-13-2003: Message edited by: aeronca65t ]</p>

Mickey Richaud
11-13-2003, 08:26 PM
Thanks, Nial. Your picture is worth a thousand words. The thought of propane or ether being sprayed around a running engine seems pretty dicey at best. Better to use the WD-40 when checking for vacuum leaks.

11-14-2003, 02:41 AM
Thanks for all the great info on worn shafts/ v. leaks. I was pretty sure a v. leak wouldn't have an effect on full throttle/high rpm's, but I had been told by someone that they had a similar problem and it turned out to be worn shafts, but maybe they misunderstood my symptoms.

Starting fluid doesn't have an effect when sprayed at the shafts, so that's good. The only thing that I haven't changed out of all the suggestions is the fuel filter. I hesitate because it seems like it's getting PLENTY of gas. I left a hose loose once and it was all over in a matter of seconds. I'll run down and get a new one tomorrow just to see what happens.

If that's not it, it's GOTTA be something in the ignition, right? There just isn't much to go wrong with those carbs! Are there any specific ignition problems that can produce those symptoms? Maybe change the plugs while I'm at it? (the ZS carb was running rich. I cleaned the plugs and checked the gap, but you never know...a friend of mine had a high RPM stumble with his Mitsu Starion. Turned out to be the plugs.)

[ 11-13-2003: Message edited by: CanyonCarver ]</p>

Mark Jones
11-14-2003, 09:03 AM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by CanyonCarver:
I still have that flat spot at over 4k that gets better with full choke, so I thought I'd give it a shot before throwing the ZS back on. I miss driving my car and I'm sick of tinkering!<hr></blockquote>

I take it that you have fitted SU's to a later model Spitfire? If this is so then the needles that are in the SU's are probably not the right ones for your car. I fitted HS4's off a UK-spec 76 to my 80 Spitfire and the needles in the carbs are incorrect for my car according to a SU reference I have.

I too have a flat spot around 3500-4000 rpm as well as a very slight hesitation when cruising at 60 mph. Both of these problems can be attributed to incorrect needles as a friend found out when he modlified his engine. He too had a hesitation at 60, which went away when the choke was applied. He tried 3 different sets of progressively richer needles before he found a set that solved the hesitation problem.

11-14-2003, 05:50 PM
The thing is that Triumph produced essentially the exact same car as mine a year earlier with the dual SU's. As far as I can find, there are no mechanical changes between '69 to '70 that would require richer needles, and I have the correct ones for a '69. But then again, it does make sense and since no one has brought up any ignition related issues I may be having, I think I'll try some different needles.

How do I go about finding some richer ones?

thanks again.

11-15-2003, 02:03 AM
Hello CC,
I made a mistake in my earlier post, I should know better but I was thinking HS2 = 1 1\8" when it is, of course, 1 1\4".
If the needles are spec, then I would look at all the engine settings, i.e do a full tune up. look also at your air filter(s) as a really dirty filter will affect the running.

Alec graemlins/thirsty.gif

11-15-2003, 02:41 PM
My Spit 1500 with twin 1 1/2" SU's had the same size needles that the UK version cars had in them, but they were too lean for my car(and UK cars had higher compression), so you probably need a size or two richer. Many things can affect needle size requirements. and change that fuel filter. They're cheap and have caused me grief in the past, with many days trying to fix a problem that was only a dirty filter.

11-16-2003, 04:03 AM
CC, try this and see if it helps.