backfires but runs great

[00squirrel]

I have a 1985 85 HP Force outboard.<br /><br />Occassionally, I'd say once ever three strats, the engine backfires. After the backfire, the engine will start and run fine.<br /><br />Any idea what could be causing this?

 

[IRCRAZYWEIRDO]

Re: backfires but runs great

maybe leftover fuel in the cylinder. I sprayed a lil gas in the spark plug hole then replaced the plug, when I turned my key on it backfired without even turning it over.

 

[00squirrel]

Re: backfires but runs great

Is it possible that the carb(s) could be letting fuel into the cylinder(s) when the engine isn't running? Perhaps a stuck or sticking float?

 

[ljshein]

Re: backfires but runs great

My 84 - 125 has the same issue. Another symptom is when you tilt the motor forward, some fuel will leak out of the carb(s). <br /><br /><br />The needle valves are worn out and not sealing properly or the float level is out of adjustment in the carb. In my case it was both. I bought a Sierra carb kit locally and found it had the wrong needle valve. I have the correct needle valves on order.<br /><br />Jeff

 

[imported_bjs]

Re: backfires but runs great

my 120 does the same thing but right after backfires the motor always starts everyone says thats normal so i dont worry about it.if it runs dont mess with it 2 strokes are to touchy.

 

[00squirrel]

Re: backfires but runs great

Originally posted by ljshein:<br /> My 84 - 125 has the same issue. Another symptom is when you tilt the motor forward, some fuel will leak out of the carb(s). <br /><br /><br />The needle valves are worn out and not sealing properly or the float level is out of adjustment in the carb. In my case it was both. I bought a Sierra carb kit locally and found it had the wrong needle valve. I have the correct needle valves on order.<br /><br />Jeff

Yes! My boat has the exact same symptom of fuel leaking out of the carb(s) when the engine is tilted up. I don't know anything about setting the float level or how to tell if the needle valves are worn. Any help in this area would be greatly appreciated.

 

[t.martin]

Re: backfires but runs great

I think all Force motors leak a little when you tilt them all the way up. That is why they have the carb covers with return lines.

 

[00squirrel]

Re: backfires but runs great

Originally posted by t.martin:<br /> I think all Force motors leak a little when you tilt them all the way up. That is why they have the carb covers with return lines.

Fuel leaks into the engine housing when the engine is tilted up, and it seems to do a little when the engine is in a running (level) position, though, not nearly as much as when the engine is tilted up. I'd still like to know how to check the float level and needle valves, if someone could help me out.

 

[t.martin]

Re: backfires but runs great

If your motor is like mine, you can't change the needle seats as they are pressed in (walbro carb). Inspect your needles for wear. To set your floats: remove carb. remove bowl. turn carb upside down. float should be parallel with carb. if not adjust by bending tab. If you have your carbs off, you might as well clean them. I recommend soaking them in mercury power tune for a couple of hours. rinse well with water. then blow every hole you can find with compressed air.

 

[ljshein]

Re: backfires but runs great

Guys,<br /><br />I can't accept the idea that the carbs are designed to leak when you tilt the motor forward. The fuel that drips from the cowling is a huge health / safety issue and I don't se how the US government would have ever let that go, even in the late 80s.<br /><br />I just got my replacement needle valves and have not installed them yet but just cleaning the carbs and resetting the float levels has reduced the leak, reduced the backfire on startup and reduced the stalling when going into gear.<br /><br />I anticipate the new needle valves should make it even better.<br /><br />Maybe I'm just anal retentive but I don't see a reason why these engines can't be made to run correctly with some time, patience and a good understanding. Especially if we all stick together and share our knowledge.<br /><br />Jeff

 

[t.martin]

Re: backfires but runs great

When you shut your motor off and tilt it all the way up there will be some residual gas in the carbs. That is why there is a return system. If gas is dripping out of the motor then you do have a problem. The gaskets on your carb cover might need replaced.

 

[00squirrel]

Re: backfires but runs great

Originally posted by ljshein:<br /><br />I don't see a reason why these engines can't be made to run correctly with some time, patience and a good understanding. <br />Jeff

I compeletely agree!