backfires

[fakeplay]

62 fishing scott mfg by McCulloch 71/2 hp. Hi I tried starting this motor today and all I got was a few backfires. my initial carb settings were 11/4 turns out. everything seems to be ok but it won't start. What next new carb ? orr just take it apart AGAIN ? thanks for any hep.

 

[keith-uk]

Re: backfires

Is this motor a twin, if so are the HT leads on the right plug, it will just backfire if not.

 

[fakeplay]

Re: backfires

It is a twin, but, I'm not sure what yer talkin bout. do you mean are the plugs wired right ? I'mnot sure thats why I' m asskin' Thanks
What's HT ?

 

[ohm116]

Re: backfires

He is from the UK so he means the high tension leads or as we would call them spark plug wires

 

[CATransplant]

Re: backfires

If the spark plug wires are switched, that can cause backfires. Easy way to find out is to switch the plug wires and try again. If it starts, you've found the problem.

Another cause of backfires is a sheared flywheel to crankshaft key. This usually happens when the crankshaft nut is not properly torqued. In your case, if you haven't had the flywheel off, then the last person who did may not have properly torqued the nut.

So...swap the plug wires. If it still backfires, you're going to have to pull the flywheel to see if the key has sheared off. I don't know the proper torque setting for the nut on that engine.

 

[steelespike]

Re: backfires

Flywheel screw torque is 400 in lbs.Interesting the 9 is 300 in.lbs.

 

[fakeplay]

Re: backfires

Thank You much I'll try it all. Thanks

 

[fakeplay]

Re: backfires

fly wheel key is ok, I didn't tourqe but will,

 

[CATransplant]

Re: backfires

If you didn't torque the nut, then the key may well be sheared now. Just one backfire can do it. It's really, really common.