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<p>A lot of niggling things there, you need to go through everything
carefully - compressions, valve clearances, timing including
vacuum and centrifugal advances and looking for slop when twisting
the rotor back and fore. Carbs checking damped movement of the
pistons going up and dropping smartly when coming down, springs,
needles, air flow and mixture balance.</p>
<p>Backfire in the exhaust or the intake? In the exhaust that can
follow a missed combustion, do you get a jump in the tach needle?
Problems with the gulp valve can also cause backfiring.</p>
<p>Check all the hoses between front tappet chest cover and carbs,
canister to carbs, rocker cover and tank including the separator
in the back. Should be a non-vented tank filler cap. A leak in
any of those can disable the anti-runon system. Check the valve,
after running and switching off the valve should click as the oil
pressure dies away. With the engine running apply 12v to the
slate/pink terminal of the valve and it should stop the engine.<br>
</p>
<p>PaulH.<br>
</p>
<div class="moz-cite-prefix">On 01/12/2021 01:10, dave northrup
wrote:<br>
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<p class="MsoNormal">Haven’t had it too long. Seemed to be
running ok; had transmission problems so we swapped out for a
good one.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Just had a very knowledgeable friend set
the timing and the carbs and the choke adjustment.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Pull the choke all the way out and it
starts ok; but seems to backfire a bit, especially when cold.
After it warms up you can push the choke back in and it runs
and idles ok except it seems to have a loss of power in the
3000 + rpm range, and does occasionally still backfire.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Has a Pertronix but other than that seems
pretty stock including the air pump. Tends to run on a bit
after you turn it off.<o:p></o:p></p>
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<br>
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