g50b issue

[Attexnoob]

I checked my compression earlier today with 180 per cylinder with good hot spark. But then i ran the engine with the gas tank high and had a sypheon engine started idled raced up then stalled from low idle. i went inside and let it sit for around a half an hour and next thing i know the plugs fowed out and it had no compression ( 30 lbs.) removed the plugs cranked the the engine and gas shot to the roof literally. Why no compression? Now im letting it sit overnight with oil in it.

[turvuren]

g50

I'm not fan of this engine and it sounds like something bad may have occured. I assume you had premix fuel in it- yamalube R is at 40 to one is a good choice. If you get it running again I would suggest retorque the heads-saw one recently where loose head led to blown head gasket and engine seizure. A really good idea would be to replace with a Briggs and settle for a slower machine.

[jerbear]

If you lost compresssion after it got hot, sounds like ring failure. After all these motors are +/- 25 years old, and who knows the abuse they have had to endure after all those years. I'm going thru one of my superchief's g50b engines right now, and i'm glad i'm doing it. After getting it apart and looking at everything....it sure needed it.

[Don]

Any way you look at it, it doesn't sound good. 180 psi is more than I've seen on a G50B, but going from that high to 30psi means something went really, really wrong. I'd pull the heads and have a look. It may be something serious.

[Joe M]

Rings went, or small hole burnt through the top of the piston.

[patb069]

G50B

Hi Jerbear. Where are you finding parts for your G50B. As far as cylinder compression my machine tested out at 196psi in the right one and 194 in the left. If 180 is high, what is going on with my motor? It seems to run great...now I am worried.

[LarryW]

Hi Jerbear. Where are you finding parts for your G50B. As far as cylinder compression my machine tested out at 196psi in the right one and 194 in the left. If 180 is high, what is going on with my motor? It seems to run great...now I am worried.

Dont be worried about it being 2 high. If it was ever bored out it will read higher. The only issue with to high comp is pre ignition or spark knock which mean you need higher octane fuel. but if its running good I wont worry about changing anything. Spark knock is a knocking or pinging sound ussually on acceleration when the engine is under a load.

[jerbear]

G50b

Hi Jerbear. Where are you finding parts for your G50B. As far as cylinder compression my machine tested out at 196psi in the right one and 194 in the left. If 180 is high, what is going on with my motor? It seems to run great...now I am worried.

I find parts all over. Complete gasket set isn't hard to find. Pistons and rings come up on ebay every so often. As far a 194-196 compression test that seems pretty high. Maybe it's just your tester. The motor i'm going thru was pullin 55-60 psi, so it was time. Maybe Don or someone could chime in on actual specs. If it's runnin good tho.....don't fix it!

[Don]

I'll have to look up the compression specs and see what the book says, but I'd be surprised if it were that high. I fiind it's usually between 140 and 160 for the G50B (cold).

I was thinking about the sudden loss of compression and the only thing I can think of is that maybe the needle/seat in the carb was stuck wide open and the engine tried to compress a liquid. The only thing is, you'd have to fill quite a bit of the crankcase up with fuel before it pumped it up to the combustion chamber. I'm not sure that's what happened, but if it is, broken rings will be a best-case scenario. There's just as likely to be broken pistons and bent rods. I'm interested to see what's up with it.