Hi Scott. There is an idle bypass valve on the Strombergs -- at least the
TR6 Strombergs. It does have an effect on the exhaust popping. The popping
is because the mixture is over-rich when the engine is being over-run. The
idle bypass leans it out.
I've also got the same problem as you with the RPM dipping way low. I'm
still trying to work that one out, but supposedly that could have something
to do with the idle bypass. Take a look at the carb section in Jay Welch's
excellent technical reference at
http://clubs.hemmings.com/clubsites/capecodbritish/technical.html. Here is
an excerpt:
"Goose" the throttle making sure the RPMs fall normally & the car does not
attempt to stall out. If it stalls out, or attempts to, the throttle
bypasses are adjusted too tight & not opening to let any air in on overrun.
If RPM falls very slowly (like it has a 100 lb flywheel) the bypasses are
too loose. Adjust as necessary. This may also affect sync & mixture so you
might need to revisit them. Loosening the adjustment screw makes the bypass
tighter, tightening the screw causes the bypass to open up.
- Hugh
> -----Original Message-----
> From: owner-triumphs@autox.team.net
> [mailto:owner-triumphs@autox.team.net]On Behalf Of Scott Tilton
> Sent: Wednesday, November 27, 2002 3:18 PM
> To: triumphs@autox.team.net
> Subject: carb adjustment
>
>
> Hey guys,
>
> First . .let me give thanks.
>
> This list has made it possible for me to daily drive and vacation in
> Triumphs for the last two and a half years now.
>
> A sincerest thanks for all the help everyone has given.
> I couldn't do it without you all.
>
>
>
> Okay, so now what's up with me an my car(s)
>
> I switched the TR-4 back from H6-SU's to the Strombergs last Sunday.
> I think the SU's were leaking fuel out the bottom, and the
> choke was WAAY to
> hard to actuate for the winter.
> On top of all that, the air cleaners were rubbing the
> underside of the hood
> a little.
> (These early carbs were on the later intake manifold . . .
> the carbs fit in
> the bubble, but not the stock air filters.)
>
> So off they came.
>
> On went the Strombergs with a couple of new o-rings in them
> to help seal up
> their floats.
>
> The TR4 Strombergs have the most simple choke in the world.
> It's pitifully easy to operate. Seems to work fairly well
> too as far as I
> can tell.
>
> I really did the bare minimum of installation . . .
> rudimentary balance of
> the carbs and rough mixture adjustment.
> Seems to have run well enough to get me back and forth to
> work this week.
>
> I do notice a couple of things . . . the engine will rev
> better up to the
> higher end . . . pulling all the way up to 5k on the tach.
> The SU's seemed to fizzle out up there. However now it seems
> to feel like
> it has weaker grunt (pull) at low RPM.
>
> Also . . . on engine braking, the exhaust has quite a lot
> more popping and
> crackling going on.
> Don't know exactly what that means, if it's a bad thing, I
> suppose I ought
> to fix it.
>
> Isn't there some sort of Bypass on TR6 carbs that is supposed
> to lessen this
> effect?
>
>
> Lastly, when I let off the accelerator (completely) the idle
> will dip way
> down to sub 500 rpm levels.
> The red ignition light will start glowing and once or twice
> the car has even
> stalled.
> Given a few seconds .. the idle will recover and eventually
> work its way up
> to 1000rpm or so.
>
> One other bit of info: no vacuum advance on this car. Its broken.
> So that port is plugged on the carbs.
>
> So those are my symptoms.
> Anyone want to hazard some guesses as to what I ought to look
> at to improve
> things?
>
> As I said . .I haven't really put a lot of effort into it
> yet, so I'm not
> stumped or anything, but I'm always open to other's ideas.
>
> Thanks as always.
>
>
>
>
> Scott Tilton
> 1963 TR4 everyday
> Leesburg, VA
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