First Generation Ascots > Tech Section

Performance problems

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triguyracer:
Shimming the needle does make a difference,the best way for me was to pull the carb this way it made removing the slide less of a problem,take the slide out and on top in the middle there is a round white plastic piece that is the stopper for wide open,you pry pull this out be carefull as it is plastic and you don't want to brake it,when this piece is removed you will be able to look down from the top and see a slotted screw,undo this and lift out the needle ,just turn upside down and it will drop out.Now find a washer to fit on the needle below where the top spacer on the needle is,I used a washer from home depot just make sure that the outside dia is the same or a bit smaller than the spacer that holds the needle if not it wont drop down all the way and your bike will run to rich,probley wont run if you don't make sure it is as small or smaller than the one on there,I had to file and trim mine by hand to make the outside dia right.The washers I used where 25 thous thick these worked real well.Some times you will be able to find very small washers on small electronic stuff,just don't over do it on the thickness a very little makes a big diff

Lefty:
Thanks, I'll start looking for washers.
I remember reading about the different "circuits" of a carb- the pilot is idle and the main & needle circuits are 1/2 to 3/4 throttle and 3/4 to WOT, right? So the main is 1/2 to 3/4 & the needle is 3/4 to WOT, right? I'll post up my results.

scottly:
Shimming the needle didn't make much, if any difference, with a free-flowing air-filter. With a stock airbox, it shouldn't be required at all. What size jets are you running, Lefty? The common set-up with the airbox seems to be a 58 with a 145?

triguyracer:
The needle is from about one third throttle to two thirds the main is a little over half throttle up to wide open they overlap to a certain degree.the needle is the midrange and the main is half or so up to wide open

scottly:
The issue with a CV carb, compared to a conventional slide carb, is that the slide (and needle) position isn't controlled directly by how far you twist the throttle; you have no idea where the slide is. From my testing, the slide is fully open by about 3500 rpm with a free-flowing air filter, requiring the large main jet. With a stock air-box, the CV carb acts very differently, and requires a smaller main.

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