Topic: model 28 wont start

[carnett3]

.004 for both

[The Tank]

A bit tight on exhaust but should run. What kind of plug?

[carnett3]

I set the valves at .004 for both

[The Tank]

Factory specs are
Intake: 0.003-0.005
Exhaust: 0.005-0.007

What kind of spark plug do you have in it?

[Michaelgc7]

If you are using a walbro carburetor or any "newer" carb for that matter the viton seals in it could have swelled and aren't sealing anymore. In walbro carburetors Briggs use a type of rubber called Viton primairily in their inlet needles and seats. The problem with this material which most people don't know is that is carb cleaner is applied to the viton, it swells. So if your carb was cleaned with carb cleaner the viton seals for your inlet needle could no longer be functioning and will need to be replaced. The proper way to clean a carb is to completely disassemble, clean with carb cleaner, rinse thoroughly under hot water and then blow dry with shop air.

Hopefully i didn't insult anyone, trying to share my knowledge with you guys.   

[redline]

Seeing that nobody asked, did you try my favorite remedy of giving it a good cussing out, and possibly kicking it?

[beaner]

I am having the same issues as you. If you have tried everything you can think of externally, it could be a worn cam or valves not closing properly.  I know the AVS motors are notorious for the cams wearing.

The 28 cu. in. AVS motor I have seems to point to the cam or maybe the valves not closing properly. I have replaced the flywheel key, spark plug, swapped carb with a known working one, checked compression, made sure the spark was adequate, made sure the push rods were straight, and adjusted the valves to spec.  The engine still backfires through the carb. The motor is getting torn down next, unless someone knows something else I may have missed. 
Matt

[carnett3]

I am going to re adjust my valves and try a working carb this coming weekend. I have a OEM replacement plug

[Bolens16]

I have only struck it once but have had a coil that, although it had spark, was faulty and the spark was happening at the wrong time causing a backfire.

[carnett3]

its a brand new coil though its only ran a few times with it on

[The Tank]

its a brand new coil though its only ran a few times with it on

Still can't rule out new components. I've gotten bad parts that would be brand new more than once.

[carolinablue]

Arc flywheel recomend's .045 coil gap also check that. I also seen broken cam's act the same way. Just gotta keep working at it till you find the problem Also check Head gasket

[carnett3]

the problem is ive sheared 4 flywheel keys, im gonna try lapping it and Torquing it down to 100 foot pounds

[carolinablue]

Are you using stock aluminum keys ? If you are change over to steel key and you also have to torque more than 100lbs.

[nip 19]

If it's lapped good you should be fine with stock keys for alignment. You just need a good seat. I have seen quite a  few that don't use keys at all.