40 hp Johnson 1961. Backfiring all the way in. Please help

[chead98]

Hi everyone. We were out last weekend and while out cruising, the idleing needle came out of my 1961 40 hp Johnson. I managed to get it back in enough to get us back to shore with a one set speed. The next morning, I fixed it and it seemed fine for a 30 minute run on Lake Simcoe. Yesterday, I flushed the gear oil and cleaned and greased the prop. Took it out today on Lake Ontario, ran fine slowly but when I reached open waters, it would open out. Everytime I tried to open it out it would bog down (slow down) It seemed to run fine a medium speed (15 mph). I ran it for about 20 minutes trying to figure out what was wrong. Maybe thing it could be something cought in the carb jet and it would push it through. Well no luck. It would bog at high speed and backfire at low speed. All the way in, it backfired as I could make no wake. FYI... The carbs should be clean as I did this already with a new carb kit. I'm thinking I set the ideling needle in wrong? Could this be the ideling needle? If I take it totally out again, how do I know where to set it again. Nut half way? Do I have to take the carb apart again? Sorry for making this so long. Please help. It's Canada Day weekend and I wanna go boating.. Thanks, Chris:blue:

 

[nwcove]

Re: 40 hp Johnson 1961. Backfiring all the way in. Please help

have a look in the top secret file at the beginning of this forum.....tons of good info!!

 

[Joe Reeves]

Re: 40 hp Johnson 1961. Backfiring all the way in. Please help

Did you manually clean the brass fixed high speed jet that is located horizontally in the bottom center of the float chamber... way in back of the drain screw/bolt? If not, do so as fuel must flow thru that jet before it has access to any other fuel passageway.

And adjust the slow speed N/V as follows:

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[chead98]

Re: 40 hp Johnson 1961. Backfiring all the way in. Please help

Hi Joe. I did fully clean the high speed jets and everything else in the carb. Although I may give it a quick clean again as it was quite simple. I will follow your instructions and adjust the S/S needle this evening. Although I noticed the needle is bent slightly, I don't think this will cause a problem. (it gets a little tight on every rotation). I find the only problem I see is the initial seating of the needle. I find that when I remove the nut, place the needle in, then put the nut back on, it usually gives me problems. Maybe it's just me. Thanks Joe for you helpful advice. Your quite knowledgeable and quite accurate. Chris