8Hp Briggs Backfiring

[solomon]

Hey guys its been a while.. Anyhow its snow season up here and my snowblower seems to be backfiring. It has an older 1970 8HP Horizantal Briggs on it. I rebuilt the engine i believe a yr ago. And never really used it. The carb was rebuilt to. It was converted to electronic ignition and the key is not sheared. It has good compression and fuel flow. It does not use an air filter, just a air box. Good compression and all gaskets good motor has i think 89psi. Starts first pull and runs good. Runs fine as i rev up the throttle, until it gets to WOT. It begins to backfire, i have adjusted the highspeed needle evry which way, but it only makes it worse, Its not a REALLY bad backfire but 1 backfire every 2 minutes or so and LOTS OF SURGING. When i reinstalled the side cover of the engine during the rebuild is it possible the governor arm didnt engage to the gear properly? because if i loosen the governor bolt and turn it lust a little each way and tighten in, the engine revs way past 3600 rpm like, 6500 and wants to go higher so i immediately kill it. What are your opinions? thanks, oh btw it has had a full valve job including gapping, and i have tried a few plugs

 

[Russ2251]

...is it possible the governor arm didnt engage to the gear properly?

No, makes no difference.

because if i loosen the governor bolt and turn it lust a little each way and tighten in, the engine revs way past 3600 rpm like, 6500 and wants to go higher

What governor bolt?
Surging usually means a lean mixture...so does backfiring, however, being governor was played with, that could be the cause. Sounds like valves are floating at extreme (bad news) rpm.
Check that all springs/linkage are in place (correct holes) and are not binding.
Check section in Briggs manual entitled "Governors" and match up illustration(s) to your set-up.

 

[mike75925]

depending on where the backfiring is occuring, couldn't it also be getting too much gas? or rather unburnt gas is building up in the exhaust pipe and igniting once the pipe gets hot enough?

 

[Russ2251]

A true backfire would be a lean mix.

 

[slideways]

Check the throttle shaft and butterfly to see if there is slop in it. That can cause an air leak and make it do all kinds of crazy things.

 

[solomon]

well the valves are brand new, and the seats and valves were cut for perfect seal, the guides are in excellent condition and the springs. No slop in linkage, should i take a video of it? On the governor Im talking about the 3/8 nut and the flat head screw to adjust the governor speed. if i turn it the slightest bit eitherway, the engine revs like crazy, which makes me think that the governor arm wasnt seated correctly internally to the governor gear, is that even possible though? If i lean it or richen it it makes the problem worse. I think i will take a video of it