MMRanch wrote on 12/02/21 at 16:36:46:That's over 61 mpg . I'll have to do it again to really believe it !
I often wonder how many motorcycles are running around and are jetted too rich. A bike that is too lean runs unevenly, surges and backfires and is a pain to ride - but a bike that is a bit too rich starts easily and really doesn't show any symptoms.....other that a sooty exhaust pipe and poor fuel mpg. A properly jetted bike runs much crisper and gets better mpg and is a joy to ride.
When I was fooling around with my engine it took me about 5 jet changes to get things perfect. (I start with a #50 pilot, #150 main and 3 washers on the needle).
The first thing I do is work on getting the pilot jet correct......the correct size will provide for the smoothest idle at 2 - 2.5 turns out. If you can turn the fuel mixture screw all the way in and the engine still runs - the pilot jet is too big......if you have to turn it out more than 2.5 turns to get a smooth idle the pilot jet is too small. (You must turn the idle speed down to around 800 rpm to get this fuel mixture adjustment correct). Some bikes are happy with the #50, some want a #52.5....and one was happiest with a #47.5....all had the stock paper air filter. (I really don't think the type of filter has much affect on the pilot jet, as the air flow is so small at idle that there will be very little difference in the flow provided by the filter.
The next thing I do is work on the main jet. I will put in bigger main jets until I can hear/feel the engine begin to "blubber" under full throttle.....then go smaller until I can hear/feel the engine is lean by being uneven - then I will choose to keep a jet in between those two extremes.
The final thing I do is set the slide needle height......I keep adding washers until I can feel the bike "surge"during light throttle settings (which shows the bike is too lean). Then I start taking away washers until the light throttle settings provide for smooth running.......in my opinion this is where most of the riding is done (1/4-3/4 throttle), and it has the most affect on fuel mpg (other than 3/4-full throttle at interstate highway speeds).
When a bike is jetted this way it runs the best when on the throttle and gets good fuel mpg. The bike may get a little noisy when you allow the throttle to close completely while decelerating (compression braking) or shifting gears - as the fuel mixture goes lean when the throttle is closed and the only fuel is provided through the idle circuit. You can easily stop the backfiring/noise by using your right wrist to crack the throttle open a very small amount and giving the engine a bit more fuel (you only need to use enough throttle to stop the noise....not enough to make the bike accelerate). And......if the bike is too noisy you can go up one size on the pilot jet and make the mixture at closed throttle a bit richer without hurting your fuel mileage.....however you may need to make an adjustment on the needle height after going larger on the pilot jet.