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meritlover
31-08-06, 10:51 AM
hello.
last weekend i did some work on my 1.2
i skimmed 40 thou off the head to increase the compression ratio, ground the valves, opened up the head all round the ports and carefully matched the manifolds to the enlarged ports. the over lap was something like 1.5mm in places so it was pretty restrictive.

the problem is now that theres a huge flat spot during accelleration, the car wants to go and the top end is so much quicker than before, it has more torque and is more responsive. over all (except for this hesitation)

when some choke is applied it cleares and pulls better, this would suggest to me that the carburation is slightly lean or the accelleration pump is not supplying enough as the flow drops across the venturi at WOT.

what should i do? should i go changing jets or adjusting the mixture screw? or will i start by increasing the stroke on the accellerator pump?

thanks in advance

Stuart
31-08-06, 10:56 AM
get it on a RR and get them to set the fuelling for the whole rev range. there is a high chance its running lean with the "improced" breathing.

meritlover
31-08-06, 11:05 AM
ive got a Zeitronix widebad O2 AFR meter so i can data log the AFR, but how do i start tuning the carb, theres surely a procedure the pros use, start with a big jet etc and work back.
what do they do?

Stuart
31-08-06, 11:47 AM
get your haynes manual out and look at how to set the carb up. if you get to the end limits of your current jet then fit a bigger one...

meritlover
31-08-06, 11:59 AM
just wondered if anyone had done this before, or had a simelar problem