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I installed a VERNIER cable in the place of the OM hand throttle, WOW what a difference, I can FINE tune the RPM by almost down to 1 rpm (total control when hot, no wonder, from idle to 2100, a bit of wonder when cold but still better then the oem hand throttle).
Getting the old hand throttle out is a bit of a chore, the start/run switch has to be removed from the dash to get your hand where it needs to be, I left mine hanging from the wires, I drilled out the hand throttle hole, If I had to do it over again, I would drill about 1/8" oversize because of the way the vernier cable needs to go in. I cut the nub end off the vernier cable to get the attaching fixture and the cable end nuts off, this is necessary to get the cable though where the old hand throttle exited the firewall. When installing the v cable, leave one mount nut AND the lock washer on the control end (dash side), as you slide it though the dash put the inner mount nut ONLY on the cable, ,then thread the v cable though the a second hole behind the dash, this hole is a bit up from the dash hole center line ( the reason for the 1/8" oversize hole), thread the cable end through the firewall grommet where the old hand throttle went, as you thread though the dash, start/thread the inner mounting nut, at some point the inner nut will be against the back of the dash, MAKE SURE a flat of the nut is up because of the primer pressure gauge is above it, there is NO clearance, then turn from the outside the v cable while retaining the inner nut from turning, once you get the v cable where you want it, tighten down the outside nut. On the firewall side, secure the end of the v cable. if needed extend the cable so it goes though the hand throttle bracket on the throttle rod, using the om cable stop fixture on the v cable, set the cable with a TINY bit slack so there is NO load on the throttle rod, adjust a bit, on the m819 I have about maybe 3/8" of shaft showing with the knob pulled out when the tach is showing 1500, think you will be surprised just what little movement of the control knob it takes to get to intended rpm, DO NOT, I repeat DO NOT pull the control knob all the way out, the pump does not have that much travel.
Well that is my hand throttle upgrade, it is well worth the effort and expense.
Getting the old hand throttle out is a bit of a chore, the start/run switch has to be removed from the dash to get your hand where it needs to be, I left mine hanging from the wires, I drilled out the hand throttle hole, If I had to do it over again, I would drill about 1/8" oversize because of the way the vernier cable needs to go in. I cut the nub end off the vernier cable to get the attaching fixture and the cable end nuts off, this is necessary to get the cable though where the old hand throttle exited the firewall. When installing the v cable, leave one mount nut AND the lock washer on the control end (dash side), as you slide it though the dash put the inner mount nut ONLY on the cable, ,then thread the v cable though the a second hole behind the dash, this hole is a bit up from the dash hole center line ( the reason for the 1/8" oversize hole), thread the cable end through the firewall grommet where the old hand throttle went, as you thread though the dash, start/thread the inner mounting nut, at some point the inner nut will be against the back of the dash, MAKE SURE a flat of the nut is up because of the primer pressure gauge is above it, there is NO clearance, then turn from the outside the v cable while retaining the inner nut from turning, once you get the v cable where you want it, tighten down the outside nut. On the firewall side, secure the end of the v cable. if needed extend the cable so it goes though the hand throttle bracket on the throttle rod, using the om cable stop fixture on the v cable, set the cable with a TINY bit slack so there is NO load on the throttle rod, adjust a bit, on the m819 I have about maybe 3/8" of shaft showing with the knob pulled out when the tach is showing 1500, think you will be surprised just what little movement of the control knob it takes to get to intended rpm, DO NOT, I repeat DO NOT pull the control knob all the way out, the pump does not have that much travel.
Well that is my hand throttle upgrade, it is well worth the effort and expense.
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