Johnson 25hp 1972 won't start, backfires after repair

Hello everybody

This is my first thread as I desesperely need help. I have an old Johnson 1972 25hp and it started doing this

http://www.youtube.com/watch?v=-i3BAs3b76Q&feature=plcp

As I had taken apart and cleaned the carb (it was already amazingly clean), I found out that there was a coil wire that was partially ripped and caused the problem. I very carefully changed the coil and put everything back the exact same way it was (flywheel, etc).

I was very enthusiast to start it again (it has ALWAYS started with 2-3 cranks) to hear it, but nothing happened. There is absolutely nothing going on, just a small backfire from time to time. I then hurt my hand, arm and back cranking it, so last night I rechecked the carb and it is very clean. Tonight I tried it again but by turning the flywheel with a hand drill instead of the crank but.. it only backfired from time to time.

Now, I see the spark on both plugs (they are kinda weak though), and I can't have switched the ignition wires as one is too short for the wrong plug. Fuel is getting to the carb and filling up the bowl correctly.

Here are my thoughts : I don't see the plugs getting very wet nor smelling gas a lot in the cylinder chamber, so I'm thinking the gas dos not get to the chamber... but it has always been perfect... My gas is brand new, no water in, etc.

I have never heard such backfires, and my spark plugs are new from last year. Tomorrow I will try something else, but I am kind of desperate here !! My wife keeps laughing at me cos I'm a mechanical engineer that can't get a motor running...

Help please !

Re: Johnson 25hp 1972 won't start, backfires after repair

Sounds like a lean miss, where do you have the low speed needle set?
Static setting should be 1 1/4 turn out from lightly seated and then fine tuned with the engine in the water in gear.
You can also use a timimg light to see if you have constant spark on both cylinders.

Re: Johnson 25hp 1972 won't start, backfires after repair

Thanks for the advice Daviet. By the way.. RickNoel, did you get it running well? I'm in the same boat as your above post (no pun intended). Cleaned out the carbs on a '98 25 hp Johnson. My Aunty's boyfriend was visiting and he's a mechanical engineer. We fired her up and she started right up. However, RPMS were really high on the muffs and she blew a spark plug out! So my aunty's boyfriend helped me helicoil and tap the threads for the spark plug to go back in. Tried starting again and nothing. Just a random backfire now! Well he had to go back to NYC so I'm trying to figure this out alone now. Took out the carb again, checked the float setting, re installed, and still nothing. Just a random backfire from the exhaust lower engine. Again took out the carb, reset the float. Still same thing. Just a backfire. no start. Help please anyone. Greatly appreciated.

Re: Johnson 25hp 1972 won't start, backfires after repair

Are you sure there is not water in the fuel? Sounds like your filter may be full of water.