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TR250: intermittent missing @ mid-range

To: Scions of Stanpart <triumphs@autox.team.net>
Subject: TR250: intermittent missing @ mid-range
From: Andrew Mace <amace@unix2.nysed.gov>
Date: Mon, 7 Oct 1996 09:23:38 +0400 (EDT)
My turn to call for help!

The car: 1968 Triumph TR250, relatively stock engine, save for headers 
and Monza (choke on fumes) exhaust. I think they are the correct 
Strombergs and, beyond some bizarre plumbing for a vacuum gauge (mounted 
deep in the passenger footwell where no one will be bothered by it!), 
all seems pretty correct.

The problem: once warm, there seems to be an intermittent sputtering/
misfire at mid-range under slight load, i.e., 2000-3000 rpm and about 
1/4 to 1/3 throttle will produce some sputtering. I've been through a 
minor tuneup, cleaning this, resetting that, checking this and that. The 
diaphragms are intact, and oil level in the dashpots is appropriate.

If it's indicative of anything, there is occasionally some very minor 
flooding (weeping is more like it) from the rear carb float bowl. (This 
one has been cleaned and checked -- figures! The front one has not been 
touched -- yet!)

Plugs look generally good, with a reddish brown color. They're NGK -- 
not my preferred brand (no flame wars please). The one thing that 
bothers me about the plugs is that it looks as if some deposit seems to 
form on them in fairly short order. On one plug I looked at yesterday, 
it looked as if it were on its way to filling the gap with this deposit. 
This, coupled with some trace of blow-by deposits in the valve cover, 
lead me to wonder if there might be more problems internally than my 
friend wants to hear about. (Yeah, it's not my car.)

Any ideas, based on the evidence thus far? BTW, this is a relatively 
recent occurence, which does lead me to suspect a poor batch of gasoline 
as one possible cause, as otherwise the engine is STRONG LIKE BULL as 
they say.

I'll entertain any and all theories short of "rebuild the da*n engine, 
you fool"; my friend would rather spend this winter having the body 
redone. As I said, basically the car is fine mechanically, save for this 
minor inconvenience.

TIA,

--Andy

  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
  * Andrew Mace                         e-mail: amace@unix2.nysed.gov *
  *                                                                   *
  * Mrs Irrelevant: Oh, is it a jet?                                  *
  * Man: Well, no... It's not so much of a jet, it's more your, er,   *
  *  Triumph Herald engine with wings.                                *
  *   -- The Cut-price Airline Sketch, Monty Python's Flying Circus   *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *



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