71 25hp wont start

[Haus]

I picked up a 71 25hp that had a broken throttle cam. previous owner said it ran great untill it broke. i replaced the cam, and now it wont start. its a rope start, has good spark on both cylinders. looks like one coil might be original, but still provides good spark, and points look good. thermostat and impeller were replaced by previous owner. put in new plugs (j6c), and the plug wires have been changed at some point aswell. did a compression test, and it seems kind of low, at 80 and 78psi.

It will not run at all, even with pre-mix sprayed into the cylinders via plug holes. would the low compression be the culprit?
any advice on getting this running would be greatly appreciated.

 

[jbjennings]

Re: 71 25hp wont start

If your gauge is accurate, the compression is low. However, they almost always have uneven compression if compression is bad so it could just be your gauge. How did you test spark? Spark could be the problem if it won't jump at least a 1/4" air gap. If so, either your compression is too low, your plug wires are crossed, or your flywheel key is sheared and the timing is off.
Just my best guess,
JBJ

 

[Daviet]

Re: 71 25hp wont start

If everything is correct, that engine will start and run with those compression numbers.
If it will not start by squirting fuel into the carb, I would recheck the ignition system, as stated before, the spark needs to jump a 1/4" air gap and be bright blue.

 

[Haus]

Re: 71 25hp wont start

i figured out what the problem was. i layed the engine down with the carb sticking up while i had it off the stand, and the float bowl drained into the engine. i guess this flooded the engine pretty bad. it sat for 2 days with the plugs out, and it fired right up today when i got a chance to play with it again.

im going to run some sea foam and see if that brings the compression numbers up.

thanks for the help