Hi Glenn:
It sounds like you may have a float level problem Possibly the floats are
set too high and the car starves at higher speeds. Another possibility is
that you have coincidentally jumped a tooth on the timing chain. Did you
have problems on starting which may have caused any backfiring?
On a motorcycle, when any changes are made to increase the flow of exhaust
gases, the carbs must be richened to accommodate the increased air flow
through the engine. You may have created an excessively lean engine with
the new system. While you can adjust it at idle, the carbs cannot
accommodate higher revs.
The final possibility is that you have an intake leak somewhere which is
leaning out the mixture. This would definitely cause backfiring.
John McEwen
>Well, I finally got the HS4's back on the primrose. But I can't tell what
>the difference between old beat-up carbs and freshly rebuilt, shiny, with
>new everything carbs is, because I can't seem to get the damn car back in tune.
>
>Along with the carbs I also installed that 1 7/8" stainless exhaust. I
>needed a new system; the old one was dented in about half and rusted
>through. It fit the primrose better than the maroon - bolted right up, and
>no fitting involved. All this, of course with new filters, vacuum check,
>valve adjustment, plugs, oil, timing, everything.
>
>So when I finally get around to starting the car up I finally found a nice
>smooth even idle at about 1k rpm and took it out for a drive. As soon as I
>get out the drive I got nothing. Sputter. No power. Yeah, it'll run, but it
>limped up to the corner. Limped back to the drive and started playing with
>it again. More test drives and still the same thing.
>
>I finally got out the Colortune and checked it, found it was running rich on
>both sides, so I dialed it back about three flats into the blue, and pulled
>the idle back down to 1k. Set the timing with the light at spec (14 BTDC)
>and started out the drive and turned right back in. Less power. Finally I
>was able to get the thing to at least accelerate and drive smooth enough to
>go get gas, nudging the timing or mixture every couple of blocks, but for
>the life of me could not get it to run smooth.
>
>The question that comes to mind is; What is the effect of opening up the
>exhaust pipe diameter on an otherwise standard high compression 18G engine?
>That is the only non-stock item in the mix. 1 7/8" pipe with a single rear
>free-flow silencer. I can't imagine that one item trashing the entire
>system, but that's the only thing different from before. Is it back-pressure
>I'm staring at?
>
>If there's anything I've missed, I'm stumped what it is.
>
>Glenn
>
>-----------------------------------------
>No one in Tuna knows what I do for a living.
>Why should they care what I say?
>
>Glenn Schnittke Recovering Musician
>Nashville TN 615-385-2800
>schnittke@mindspring.com
>
>-----------------------------------------
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