casual_daze
Cadet
- Joined
- Sep 17, 2009
- Messages
- 11
Hello
I have a 1969 3.9hp and an early 1970's 4hp. The bottom end on the 3.9hp is shot and the 4hp has no spark so I decided to switch the lower case on the motors to get one good one. the case looks the same but the shifter rod on the 4hp was longer so I swapped them (wasn't easy to line everything up to get it back in... does anyone have any tips for doing this?). The only other visual difference is the water pump/impeller. The 3.9hp has a little pin in the shaft to spin the impeller and the water pump housing is metal while the 4hp has a key to operate the impeller and the pump housing is plastic. The pump looks the same so I decided to use the plastic pump.
Everything goes together well until it gets to the final 1-2mm, I then have to use the wrench to tighten the nuts to bring it together (not much pressure to get them together using the wrench). The problem is... when its together the motor is very tight to turn over by hand using the flywheel (spark plug out), but when I loosen off one of the nuts to allow the gap to come back... the motor turns over easy.
Does anyone know what I did wrong or does a 4hp bottom end not fit onto a 3.9hp?... does the 3.9hp have the parts I need to get spark back into the 4hp?
Thanks
I have a 1969 3.9hp and an early 1970's 4hp. The bottom end on the 3.9hp is shot and the 4hp has no spark so I decided to switch the lower case on the motors to get one good one. the case looks the same but the shifter rod on the 4hp was longer so I swapped them (wasn't easy to line everything up to get it back in... does anyone have any tips for doing this?). The only other visual difference is the water pump/impeller. The 3.9hp has a little pin in the shaft to spin the impeller and the water pump housing is metal while the 4hp has a key to operate the impeller and the pump housing is plastic. The pump looks the same so I decided to use the plastic pump.
Everything goes together well until it gets to the final 1-2mm, I then have to use the wrench to tighten the nuts to bring it together (not much pressure to get them together using the wrench). The problem is... when its together the motor is very tight to turn over by hand using the flywheel (spark plug out), but when I loosen off one of the nuts to allow the gap to come back... the motor turns over easy.
Does anyone know what I did wrong or does a 4hp bottom end not fit onto a 3.9hp?... does the 3.9hp have the parts I need to get spark back into the 4hp?
Thanks