jchrisk1
XS650 Junkie
What effect does plugged bypass holes have on the pilot circuit?
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Carb question
- Thread starter jchrisk1
- Start date
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- Tags
- carburetors
When you twist the throttle, the engine does not increase rpm.
On the 650 carbs, the pilot circuit feeds it's air/fuel mix into the main bore through 4 tiny holes. One comes from the mix screw and it's flow can be regulated by that screw. The other 3 flow directly from the jet. These are the bypass holes. If they're plugged, you could lose up to 75% of the pilot circuit flow.
jchrisk1
XS650 Junkie
So if a one or two of these are plugged it could resemble a lean condition? I've got too big of pilots in my 78-79 38's (35's) and it still seems to be running lean on the left side. I've checked for leaks and can't find any. I'm going to have to clean that again and make sure because I think I remember one of them not flowing out as much when I shot cleaner through it.
Yes, it could (probably would) create a lean condition. You can attack the cleaning from 2 points. You can spray cleaner (and blow through with compressed air) up through the pilot inlet on the bottom of the body and also through the mix screw hole. When coming at it from the mix screw hole, block the pilot jet hole and the mix screw outlet into the main bore so the cleaner is directed only out the 3 by-pass holes. When coming at it from the pilot inlet, block the mix screw hole and it's outlet into the main bore. When you're done with the carb cleaner, blow WD40 through the circuit to flush the remnants of the cleaner out.
jchrisk1
XS650 Junkie
I will try this tomorrow and see if it improves. I have new 30 and 32.5 pilots coming tomorrow so I will tackle it all at once.
