B&G 5hp engine wont turn over, seems to be exhausting through the carb

[DrFistington]

I have a wood chipper that had been giving me some grief lately, it has a B&G model 135212-1196-E1 5hp engine. The initial issue was that the engine would start up if I put some gas in the spark plug hole and gave it a few pulls, but it would quickly die. I cleaned out the carb since it was gunked up, but was still running into the same issue. When I looked at the cylinder and valves, it seemed like the exhaust valve wasn't sitting evenly and was a bit too high when it should be closed. I decided to relap both valves, but now it seems like the problem hasn't been fixed, and has changed slightly.

I was able to look at the valve retainers again and the exhaust valve retainer seemed to be cocked a little bit, so I adjusted it so its sitting flush now, and i put everything back together and tried to start it up with starting fluid. I would have to continually pull the rope and eventually the engine would start trying to turn over, and I could hear some combustion, smoke would start coming out of the top of the carb where the air filter would attach, and then i would see a pop of blue flame in the carb in the same spot. At that point it seems like all the starter fluid is used up and the engine settles back down.

It looks like there are two valve retainers for the exhast valve on this model, one clips onto the base of the valve on the bottom of the spring, and the other acts as a guide for the stem and sits on top of the spring. I'm wondering if maybe I have the retainer on the top of the spring upsidedown? Then again, at this point it seems like the problem is originating more from the intake valve than the exhaust, although the intake valve seems to be seated correctly and sealing. Does anyone have any suggestions/insights?

 

[Mkala]

Hello,

You never had an hard stop of the engine ? Could be the flywheel key sheared, this cause timing issue.

For the valves, they are known to to lose lash and burn if you don't set it again correctly. You should lap them to see if they seal all around.
If you have questions about precise point, please put pictures its more easy to understand things right.

If you want some I was working on this one last year (132200, note exactly the same model) : https://www.lawnmowerforum.com/threads/briggs-5hp-ic-generator.52044/
And recently I started on this one (same serie) : https://www.lawnmowerforum.com/threads/briggs-5hp-flathead-i-c-overhaul.59229/

 

[bertsmobile1]

Did you reset the valve lash ?
Side valves tend to burn the seats so the lash gets less & less over time thus the valves open too early & close too late.

 

[Romore]

By exhaust valve retainer are you referring to the seat (ring) it sits on? That indicates severe overheating. It can be staked into place with a flat punch but if that doesn't hold the block is junk.

 

[DrFistington]

Thanks for the advice, I had made sure to check the flywheel key and that was good, and there hadn't been any hard stops. Its sounding like it may be a valve lash issue, so I'll try checking that next. From what I can tell the valve laps are good and the valves are closing sealing when they are closed.

Also, by the valve retainer there are two pieces I'm referring to (at least on the exhaust valve) in this model. At the bottom of the valve spring there's one disc retainer with a hole and notch (keyhole style) that slides onto the base of the exhaust valve stem, and then there's another disc that seems to act more like a guide, and it sits on the top of the valve spring and the exhaust valve stem passes through it. I think I have the guide/retainer installed correctly, but it could be upside down, its hard to tell from the diagrams I've found.

 

[DrFistington]

Did you reset the valve lash ?
Side valves tend to burn the seats so the lash gets less & less over time thus the valves open too early & close too late.

Are there any good posts/videos you could point me towards that show how to adjust the valve lash on a side valve engine?

 

[Tinkerer200]

Sounds to me like you are referring to a valve seal as a second retainer which should be on the Intake valve IF it has a seal. Also, some discharge out the Intake Valve thru carb is normal at start and is the result of the Easy Spin cam grind which relieves a little compression for ease of starting. I can send you a Service Manual which should cover your engine IF you like. Address below, put in proper format and remind me what you want.
Walt Conner
wconner5 at frontier dot com

 

[bertsmobile1]

You measure he valve gap when the springs are in place
If too big you grind the seats to move the entire valve close to the cam follower
If too small you grind the end of the valve stem.
Side valve engines tend to close up the gap. particularly on the exhaust valve