I did spend time with my carb on April fool's day. If all AFD were as
good. I sat down with the SU Carburetters Tuning Tips & Techniques
Brooklands Book (which I highly recommend based on the day's events) and
checked out the pretuning steps. Especially the ones that set the jet
height. I went back to the carbs and lo and behold, the difference
between the jets could be measured at about 0.4 cms. So I set to
equalizing them. The front carb jet adjusting screw worked well, but
when I tried to move the rear j.a.s., nothing happened. Voila I said to
myself. An obvious problem.
I used some spray I had for releasing frozen parts and after a few
moments I could move the jet. Took a bit, but when I finally got it to
move a tad, I resprayed it and that released it to be as fluid as the
other. Resetting the pair, with trepidation, I started the engine. No
problem. Black smoke no longer eminated from the tail pipe (at least not
like it had).
I let the engine warm up, set the idle by ear, and drove off to
visit the ex-president of the local Bitish car club. Gave me a chance to
up the RPM above 4000 and lo....no backfire. No loss of power. No
sputtering. Wow. Engine still a bit rough, but now I am in the tweaking
zone, not repair zone.
In retrospect the clue came from the Tuning book. A pretune step is
to raise the piston with the lifting pin and the carb with the frozen
jet had a lifting pin that was difficult to move. It, too, was slightly
frozen. I lubed it to smooth out its movement and realized the piston
moved fine. Then I could see the jet easily with the lovely outcome.
The car still backfires a bit, but nothing like before. I suspect
the timing is off some.
Thanks to several listers for good tips. All in all a decent
April Fool's Day....and I'd love to buy a new TF!
Bill
On
Sat, 1 Apr 2000, David Councill wrote:
> My original reply, quoted below Paul's reply, is hopefully not too far
> offbase. My carb experience, although extensive, applies mainly to the HS4
> carbs and not the HIF series. Bill's original problem was with the HIF
> carbs and in my haste I did not take this in account. Instead of the nuts,
> there is a jet adjusting screw on each carb.
>
> Thus, the steps will be a bit different but I'd still check float height
> and fuel mixture settings. Perhaps one of you HIF guys can detail out the
> steps better - Bill says he'll be checking the carbs out today.
>
> David
> 67 BGT
> 71 BGT
>
> At 04:32 PM 4/1/00 +0100, Paul Hunt wrote:
> >Paraphrasing the Workshop Manual - "turn the nuts up untill the top of the
> >jet is flush with the bridge, then turn down 12 flats".
> >
> >PaulH.
> >
> >----- Original Message -----
> >From: David Councill <dcouncil@imt.net>
> >To: <mgs@autox.team.net>
> >Sent: Friday, March 31, 2000 7:04 PM
> >Subject: Re: help with diagnosing carb settings?
> >
> >
> > > Sounds like fuel starvation. Check float bowls. May need to adjust them to
> > > allow more fuel into the bowls. Also check jets to make sure mixture is
> >set
> > > right. Initial setting is "12 flats" - turn the nuts all the way up and
> > > then loosen 12 spots on the nuts which I believe is two full rotations
> >out.
> > >
> > > David
> > > 67 BGT
> > > 71 BGT
> > >
> > > At 12:22 PM 3/31/2000 -0500, you wrote:
> > > >So I replaced a ZSin a 76B with dual HIF's and the engine started. That
> >is
> > > >a good start but it is not good enough to drive. Here is a symptom that I
> > > >don't understand and could use advice.
> > > >
> > > >i) The car starts fine.
> > > >ii) Driving in 1st & 2nd, <2200 or so RPM, no problems that I am aware.
> > > >iii) When I go into 3rd and rev up to about 3000, the car starts
> > > >hickuping(?) and sputtering and jerking.
> > > >iv) Into 4th, the RPM goes down (good!) and the car smooths out until the
> > > >RPM go up with speed.
> > > >
> > > >Being the 1st timer with tuning, I could use any suggestions about what
> >to
> > > >look at and where to change settings.
> > > >
> > > >TIA,
> > > >
> > > >Bill
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