[TR] Dieseling and pinging

Wayne rengrave at verizon.net
Thu Oct 1 19:43:01 MDT 2009


Randall you are right, I have the stock distributor with vacuum retard, not 
advance, my mistake.
I am ignoring the vacuum retard and ignoring the 4 degrees ATDC.
I tried moving the distributor clockwise and ccw with the engine @ 800 rpm 
idle.
I added higher octane fuel 89 I think, and I still get dieseling.
I think I need to adjust the carbs (am not sure about this procedure).
Any instructions for adjusting ZS 175 carbs ?
What to set first, staring point?
The Bentley manual instructs me to raise the piston inside the carb air 
inlet 1/4",
and if the engine idle has an immediate increase, it means the carbs are set 
rich, if not the carbs are weak.
If the idle slightly increases and then returns to normal, then the carb 
mixture is correct.
The Bentley manual also steps me through a lot of adjustments to the carbs.
Should I touch the carbs to try and fix my pinging and dieseling issue?

Wayne
73 TR6

----- Original Message ----- 
From: "Randall" <tr3driver at ca.rr.com>
To: <triumphs at autox.team.net>
Sent: Thursday, October 01, 2009 10:56 AM
Subject: Re: [TR] Dieseling and pinging


>> The head was shaved to raise the compression
>
> Perhaps someone else knows if this applies to a TR6; but I know that on a
> TR3 motor it is important to round the sharp edges created after shaving 
> the
> head.  Otherwise, the edges cause pinging and dieseling.
>
>> My question is do I have to run high octane fuel or fuel additives or can
>> I adjust the ZS carbs?
>
> To take advantage of the higher compression, you need the higher octane
> fuel.  You _might_ be able to get by on regular without pinging, by
> retarding the ignition timing.  However, this will reduce both performance
> and mileage; to likely worse than it was with a stock engine.
>
>> What causes this? Will carb air/fuel adjustment fix it?
>
> It may get better over time, if you get the mixture and timing right. 
> It's
> caused by something in the cylinder (other than the spark) being hot 
> enough
> to ignite the fuel; which can sometimes be carbon from rich mixture or
> misfiring.  But given your story, I doubt it will get better by itself.
> You'd best learn to kill the engine with the clutch, just after you turn 
> the
> key off.
>
>> with engine @ idle 800 RPM, and the vacuum advance
>> still attached,
>
> A US-spec 73 would not have had vacuum advance originally; has someone 
> tried
> to add it?
>
>> I was no where near 4 ATDC.
>
> So where was it?
>
>> Should I be concerned that my
>> vacuum advance is not working?
>
> The stock setup on a 73 was vacuum retard only.  The VR was purely for
> emissions control and not very good at that.  So my suggestion would be to
> leave it not working, and ignore the 4 ATDC timing figure.
>
> If it has been modified for vacuum advance, then the advance would not be
> working at idle anyway.  VA is primarily for improved fuel economy 
> (although
> it does increase NOx emissions somewhat) so if you have it, I would 
> suggest
> getting it working.
>
> But the bottom line is that you need to figure out what you have, in order
> to know how to adjust it.
>
> Randall
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