Tornado
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Reviving this old thread on using the Morgan Carbtune. I was having trouble getting my new premiers dialed in. As I've no proper experience working with dual carbs (was running single Amal on my 850 most of past 3 seasons of ownership), I just couldn't know for sure which way to be adjusting things and was likely going well off the reservation.
The Carbtune Pro was very reasonably priced as 59 Pounds plus 8 more for Royal postage from UK. Got to west coast of Canada within 10 days...no duty and no tax (usually hit or miss or due to total over a cetain point).
Got it all hooked up, right side up (can be used upside down to give better response for lower vacuum level bikes). Right away I could see left side showing way lower rod position (thus less vacuum). Tweaking air stops got both sides even...but had to think it over a bit that the faster air flow (less-open slide) means lower air pressure, higher rod reading. Then with a few higher rev holds, noted again left side much lower rod than right. Found left side cable adjuster needed quite a lot of slackening to get rods to stay in unison when throttling up. All these adjustments were done immediately following dowel movement evenness and slide movement/max position checks. I think using drillbits/dowels for balancing is just a proxy as it cannot take into account real air flow, just the physical characteristics of the slides/cables....which in the real world are not identical. Also wonder if having the choke slides out, leaving big holes in the throttle slides, giving weird air flows etc., has a significant role here.
Initial Carbtune dial in was without air cleaner attached and vacuum pipes attached at the manifold balance tubes. Re-fitted air cleaner. No appreciable difference in balance, though needed a bit of idle stop adjusting (done evenly). Had heard the balance pipe going back on would mess up the idle point again but found this not to be a problem on my bike.
At least now I have a valid, repeatable starting point for further run testing. Really seems to be a good thing to have for a rookie Commando owner.
The Carbtune Pro was very reasonably priced as 59 Pounds plus 8 more for Royal postage from UK. Got to west coast of Canada within 10 days...no duty and no tax (usually hit or miss or due to total over a cetain point).
Got it all hooked up, right side up (can be used upside down to give better response for lower vacuum level bikes). Right away I could see left side showing way lower rod position (thus less vacuum). Tweaking air stops got both sides even...but had to think it over a bit that the faster air flow (less-open slide) means lower air pressure, higher rod reading. Then with a few higher rev holds, noted again left side much lower rod than right. Found left side cable adjuster needed quite a lot of slackening to get rods to stay in unison when throttling up. All these adjustments were done immediately following dowel movement evenness and slide movement/max position checks. I think using drillbits/dowels for balancing is just a proxy as it cannot take into account real air flow, just the physical characteristics of the slides/cables....which in the real world are not identical. Also wonder if having the choke slides out, leaving big holes in the throttle slides, giving weird air flows etc., has a significant role here.
Initial Carbtune dial in was without air cleaner attached and vacuum pipes attached at the manifold balance tubes. Re-fitted air cleaner. No appreciable difference in balance, though needed a bit of idle stop adjusting (done evenly). Had heard the balance pipe going back on would mess up the idle point again but found this not to be a problem on my bike.
At least now I have a valid, repeatable starting point for further run testing. Really seems to be a good thing to have for a rookie Commando owner.
Morgan Carbtune - carburetor synchronizer for balancing motorcycle carbs
Carbtune motorcycle carburetor synchronizers;polycarbonate tool pouchs;for motorcyclists
www.carbtune.com
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