1962 Lark 40hp

[zgbgwfs]

I have a 40hp 1962 lark. Model number 35531. I cleaned, rebuilt and synced the carb because of a lean sneeze. I also filed and gapped the points. Now there is no more lean sneeze but the motor seemes to have a medium size backfire of sorts in it at higher rpms. It shows up when you go past an idle but will dissappear if you back off the throttle. Anyone have any ideas what might be causing this?

 

[F_R]

Re: 1962 Lark 40hp

I have a 40hp 1962 lark. Model number 35531. I cleaned, rebuilt and synced the carb because of a lean sneeze. I also filed and gapped the points. Now there is no more lean sneeze but the motor seemes to have a medium size backfire of sorts in it at higher rpms. It shows up when you go past an idle but will dissappear if you back off the throttle. Anyone have any ideas what might be causing this?[/QUOTE

Worn clutch dog. It isn't backfiring, it is coming out of gear, rotating 180 degrees and slamming back into gear. Some people describe it as feeling like a misfire or backfire, but most describe it as feeling like they ran over a log. Or, here in FL, like they ran over a 'gator.

 

[zgbgwfs]

Re: 1962 Lark 40hp

Well, it does it in neutral, so it must be somthing else. any other ideas?

 

[lindy46]

Re: 1962 Lark 40hp

Have you had the flywheel off? Possibly a sheared key on the shaft?

 

[zgbgwfs]

Re: 1962 Lark 40hp

Yes, I had it off. I am going to go back under there tomorrow and recheck the points gap and the key. Also I think the lever the throttle control arm hooks into seems very loose. Do you think this might cause a problem?

 

[zgbgwfs]

Re: 1962 Lark 40hp

bump

 

[tx1961whaler]

Re: 1962 Lark 40hp

I'd continue with looking at the points. Make sure the magneto plate isn't too wobbly when you're under there.

As another check, spray some carb cleaner around (not in) the carb and fuel lines when it's running to check for vacuum leaks. Also try pumping the primer bulb when it's acting up

 

[samo_ott]

Re: 1962 Lark 40hp

Some people describe it as feeling like a misfire or backfire, but most describe it as feeling like they ran over a log. Or, here in FL, like they ran over a 'gator.

Better a 'gator than a manatee eh!

 

[coolguy147]

Re: 1962 Lark 40hp

dont fiel them use 400-600 grit sand paper then gap them at .020




jump ran over that gator but now there complaining about manatees

 

[F_R]

Re: 1962 Lark 40hp

Well, it does it in neutral, so it must be somthing else. any other ideas?

What are you doing revving it up in neutral? You are causing the vacuum cut-out switch to operate. That is, if the vacuum cut-out switch is still there. Too many people don't understand it and just yank it off.

 

[tx1961whaler]

Re: 1962 Lark 40hp

What are you doing revving it up in neutral? You are causing the vacuum cut-out switch to operate. That is, if the vacuum cut-out switch is still there. Too many people don't understand it and just yank it off.

..and I have had a mildly intermittent vacuum switch cause the same issue (high speed cut-out) during normal running. Took quite a bit of time to find that problem, since it tested just fine on the bench....

 

[Willyclay]

Re: 1962 Lark 40hp

Sent you a PM