Backfiring

[Anonymous-0]

Guys,
I've got an 8n, front mounted distributor. I've had it about ten years, it's always been easy starting. It didn't start about a month ago. I did a tune up, and replaced the rotor and cap. I also cleaned the carburator. Now it starts, but harder than before. It idles nice, but at about 3/4 throttle it backfires. I have a fuel filter, the flow seems normal. Any ideas? Could it be the advance springs on the distributor?
Thanks, Jerry Barth

 

[Anonymous-0]

Sounds like a worn out part in the distributor. Use a dwell meter and watch for steady dwell as you speed up the engine. At some speed, the points may either not close or not open and cause that problem.

 

[Anonymous-0]

I'm about the same age as your tractor and I backfire a
lot more than I used to, about 3/4 throttle is the worst.;-)

 

[Anonymous-0]

Backfiring is generally a problem with ignition... usually timing. May be a worn part in the distributor, or the points cam.

 

[Anonymous-0]

Backing firing can be caused by a couple things. #1 is that its running lean and that will cause the problem. You also say you have a filter, is that an in-line type filter if so take it out they cause more trouble then there worth. Plus on an 8N you have or should have 3 filters in the system any how. 1 in the tank, 1 in the sediment bowl and 1 in the elbow on the carb. In-line filters are made for systems with a fuel pump and take 7 plus PSI to work like they should and theres no way you will get that type of pressure from a ravity flow fuel system
<ul><li><a href="http://www.geocities.com/trants_mrg/ourhobbyfarm.html">Hobby farm</a></ul>

 

[Anonymous-0]

That's funny cause all my lawn tractors have inline fuel filters does mean I should get rid of them to.
Walt

 

[Anonymous-0]

Inline filters specified for Lawn and garden (and Motorcycle) gravity feed are usually more open filter material, less pressure needed for flow, keep using them. RN

 

[Anonymous-0]

I have seen that backfiring caused by a failing coil. When it fails completely the backfiring stops. So does the engine.

 

[Anonymous-0]

Actually this could be a lot of things. A bad coil, a bad condenser, Point bounce, a valve hanging up at high speed. A week valve spring. Bad gas. Water in gas. What you need to do is take each thing and check it out throughly till you find the problem. That is what a good Mechanic does don't guess just go though the entire system one thing at a time. Start with the easiest thing and work back to the hardest sooner or later you will find it and along the way you will learn a lot about how your engine works.
Walt