Re: need help with 40hp nissan
In order to get into specifics, we need your actual model and serial numbers. Year is not important for servicing, but model/serial is critical. First thing you will need is a Factory service manual for specifications and test techniques. If you have the 2-cylinder NS40C, you will want Part #003-21035-1, $44.17; If you have the 3-cylinder 40D or D2, you will want Part #003-21036-1, $44.17, available from any dealer, including me. Since you mentioned carbs (plural), I'm guessing that you have a 3-cylinder D or a D2. That being the case, a manual is very important so that you can do the link-and-sync correctly.
In general, if the plugs came out white, you are probably lean enough to burn a piston. Always check compression to see the mechanical health of the motor. Or... If you accidentally ran without adding oil to the gas (if it's not an auto-mixing model), you may have scraped down the rings, pistons, and cylinders. which might allow the motor to barely run but nothing more. Likewise, if the fuel system is loaded with crud (check all the way from the carb to the tank), or a carb needs cleaning, (or if the fuel filter is plugged) (any of these from sitting for a coupla years), you might idle OK but not deliver enough fuel for more than idle. If you decide to clean the carbs, don't cut corners -- fully disassemble each one -- I mean completely -- and soak each one in real carb dip (such as Tyme) for about 4 hours at room temperature. Then you can blow out the carb passages, reassemble, and reinstall them.
