voyageurpursuits
New member
Having trouble tuning the low speed on this motor (1976 25hp rope start). All new ignition components, carb cleaned (soaked in solvent and blown clean) with all new gaskets. 7/16" spark gap on both plugs now. I have a compression tester on the way but don't have measurements yet. Seems to run awesome one throttle plate opens (linkage lined up to begin opening just at second mark on cam) and really hums up to WOT.
However, I have to have the tiller handle set on "FAST" to start and it won't idle down below "START." I know that the tiler handle markings are suggestions but it seems to be running too fast. I read somewhere here that I should be able to idle down to where I can see the flywheel teeth but I'm nowhere near that. My main concern is shifting at too high RPM and causing extra wear/damage to gears.
Here's the procedure I went through last night:
Before starting, I turn low speed needle valve in until it seats and then back out 1-1/2 turns. In gear on lake, I lower speed (using tiller handle throttle) to where it barely stays alive. Motor vibrates a lot at this stage. Turning needle valve in does not seem to affect idle speed at all, but after 1/2 turn the motor will begin to cough and sneeze (too lean?). Turning needle valve out does not seem to affect idle speed either but after 1/2 out it seems to bog down and run rougher. Either way, I don't get to work throttle down any more than it is.
I have the throttle cam and link set per the manual to just begin to open the butterfly as it reaches the second mark on the cam. When I have it running about as slow as I can get it, the cam is still in about this position. Any past that it wants to die. Could it be that the low speed valve is plugged and not letting any/enough gas though, so that it only wants to run with the throttle butterfly valve open or about to open?
Is it worth pulling the carb apart and cleaning again? Maybe I didn't do a good enough job the first time, especially around the low speed valve. I did pop the core plug and thought it was all clean. My other thought is to decarb, as it's probably never been done and I can see the fouling in the cylinders through the plug holes. Not sure if this can improve idle, however. Also I have thought about going back to the J6C plugs instead of the J4C. It had J6Cs in it when I got it but I replaced them with the manual-recommended J4Cs.
Any insight or ideas would be greatly appreciated. Thanks!
However, I have to have the tiller handle set on "FAST" to start and it won't idle down below "START." I know that the tiler handle markings are suggestions but it seems to be running too fast. I read somewhere here that I should be able to idle down to where I can see the flywheel teeth but I'm nowhere near that. My main concern is shifting at too high RPM and causing extra wear/damage to gears.
Here's the procedure I went through last night:
Before starting, I turn low speed needle valve in until it seats and then back out 1-1/2 turns. In gear on lake, I lower speed (using tiller handle throttle) to where it barely stays alive. Motor vibrates a lot at this stage. Turning needle valve in does not seem to affect idle speed at all, but after 1/2 turn the motor will begin to cough and sneeze (too lean?). Turning needle valve out does not seem to affect idle speed either but after 1/2 out it seems to bog down and run rougher. Either way, I don't get to work throttle down any more than it is.
I have the throttle cam and link set per the manual to just begin to open the butterfly as it reaches the second mark on the cam. When I have it running about as slow as I can get it, the cam is still in about this position. Any past that it wants to die. Could it be that the low speed valve is plugged and not letting any/enough gas though, so that it only wants to run with the throttle butterfly valve open or about to open?
Is it worth pulling the carb apart and cleaning again? Maybe I didn't do a good enough job the first time, especially around the low speed valve. I did pop the core plug and thought it was all clean. My other thought is to decarb, as it's probably never been done and I can see the fouling in the cylinders through the plug holes. Not sure if this can improve idle, however. Also I have thought about going back to the J6C plugs instead of the J4C. It had J6Cs in it when I got it but I replaced them with the manual-recommended J4Cs.
Any insight or ideas would be greatly appreciated. Thanks!