----- Original Message -----
From: <jimmuller@rcn.com>
To: "TR List" <triumphs@autox.team.net>
Sent: Wednesday, June 13, 2007 3:27 PM
Subject: Re: [TR] TR4 Cutting Out Under Load
> Ed Purcell wrote:
>> They say the carbs are usually not the problem, but it sure
>> looks like mine are messed up. To reinterate, I have
>> excellent idle and operation at low RPM. Cutting out
>> starts @ about 2K under load. I can nurse it up to about
>> 3K max. Also cuts out worse up hill. Thanks again.
>
> Sorry, I don't recall the details of the original post.
>
> Did you not recently install an electronic dizzy? One way that might
> screw up your carbs is if a vacuum line got neglected and is now sucking
> air. Perhaps you richened them at idle to make it run okay? At speed
> that air leak would become less significant so that it would be too rich.
>
> Here's another idea. Your tale sounds vaguely similar to my experience
> with the SUs a PO put on my GT6.
>
> I could dial in the idle mixture okay, but at speed it had two features.
> When cruising it would miss, especially after it had warmed up, seeming to
> be too lean; under full throttle it ran like a racehorse. Playing with
> the idle mixture didn't really help. Eventually I figured out that both
> the springs and the needles were wrong. The PO had used late-model MGB
> carbs. The needles were too thick so it was too lean for cruising. At
> full throttle the pistons would hit maximum excursion too soon, resulting
> in a venturi that couldn't open any further, which richens the mixture at
> higher flow rates.
>
> If your carbs haven't been touched then this isn't your problem. But
> perhaps you've had a piston spring break? Or a diaphram split?
Jim, There are similarities. I recently installed a Pertronix distributor.
It ran well for a couple hundred miles. I attempted to adjust the mixture
due to rough idle. Things went from bad to worse, so I then readjusted
idle, sync, and mixture back to three turns below bottom of piston. I now
have the symtoms listed in my last post. I put the old distributor (with
wires) back in with no change. I do not use vacuum advance. I will try the
coil next and then I suppose a full rebuild on the carbs. Can't do it for a
while tho. Too many balls in the air. If I ever find the gremlin I will
advise the list.
Ed Purcell
Clinton, TN
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