Posted By : Chris Taylor, 26-Feb-2007,
05:12pm
Well, without wishing to be rude, one has to ask how much of a Triumph Specialist you are using if they make comments like these but cannot suggest a
solution.
First of all, it is not the head alone that dictates how much fuel/air mixture the engine flows. It depends on the camshaft as well as the manifolds,
exhaust and CARBS. I have never heard it suggested that the carbs won't work because they are being asked to flow too much; where carbs are too small
to enable the maximum to be extracted from the engine in its state of tune, they should work fine up to (and including) their maximum flow rate; at
that point the engine should still run ok, but will not produce its theoretical maximum output. And at 3000rpm any Triumph engine is WAY short of its
maximum output and standard Strombergs will be WELL within their capabilities.
Now that is not to say that you do not have symptoms of the wrong needle, but the first checks should be that the carbs actually have the standard
factory needles and air valve springs, and that the needles are STRAIGHT. Clean floatchambers and correctly set floats are also pretty obvious checks
before assuming that the needles are wrong. Then, if problems seem to be weakness at higher revs, it is worth checking the fuel system to make sure the
carbs are being kept full of fuel. Again, the standard mechanical pump should be well able to provide enough fuel for Strombergs at maximum output.
It is more likely that some DPO has fiddled with the carbs rather than there is a major mismatch between head and carbs. Make sure everything is
standard in terms of equipment and settings before persisting with more fiddling!
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Posted By : Don Cook, 27-Feb-2007,
02:03pm
3000 rpm...my distributor started to pack up about then, now solved!
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Posted By : David Lloyd, 28-Feb-2007,
08:42am
Thanks both for you feedback. I wondered about whether it was electrical, but the garage has told me that as pulling out the choke at 3000
stops the cutting out it can't be that nor a blockage I suppose. The reason the garage is having an issue is that I cannot tell them what has
been done to the head nor cam so there could be a choice of 20 or so different needles and they believe that it would be better to find a
rolling road (they think that there may be one near them in Peterborough), so if anyone knows of a good specialist with one of these in the
Cambridge or Central London area that would be great.
Cheers
Dave
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Posted By : Chris Taylor,
28-Feb-2007, 02:30pm
A rolling road would be the ideal for optimising the mixture for your engine, taking into account its spec, AND state of wear and carbon,
and modern fuels.
BUT, before spending the money, I would want to be certain that they have checked that the carbs currently have the STANDARD needles, AND
air valve springs (if any are specified), that the needles are STRAIGHT and properly secured, AND that the float chamber fuel level is set
correctly. Without that you cannot expect the carburettors to perform as expected.