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I'm starting a new thread to report the problem I identified that was causing the B&S Quantum engine to not run.

I pursued a variety of bad fuel-dirty carb solutions, none of which helped a bit.

Someone suggested checking the spark and opening the head to verify that the valves were working. The spark and valves were OK, but getting into the head caused me to disassemble the engine enough to find the actual problem:

The carb in the quantum engine fits against an O ring on the engine. The O ring is on a plastic part that conducts the fuel mixture to the port for the valve for fuel.

I found that plastic part to be cracked all the way around it, which prevented fuel from being sucked from the carb into the engine.

Result ----engine would not run. Has anyone seen that happen as a broken part before?

When I identified that as the problem, I easily found a replacement part from a junk quantum engine, and the old carb and the engine would now run..

However, I created another problem I need help with.

After starting and running OK briefly, the engine slowed down and stopped. Investigation showed that the piston appears to be off center, causing friction and making the engine hard to turn by hand.

I did take the head off to check the valves, but I didn't do anything else that I know of that would have caused this problem,

Fix one problem -----create another.

Cab anyone tell me what I did and how to fix it?

Bent connecting rod maybe?

The blade will make only a part of a revolution either direction before coming to a stop.

Darn! After putting a lot of time and effort into repairing that "wont run" problem, I really wish I had a chance to admire my effort before something else failed.

I suppose I'll tear into the engine to identify what's bad, and consider whether I can fix it with my limited skills.

seattlepioneer said:

The blade will make only a part of a revolution either direction before coming to a stop.

Darn! After putting a lot of time and effort into repairing that "wont run" problem, I really wish I had a chance to admire my effort before something else failed.

I suppose I'll tear into the engine to identify what's bad, and consider whether I can fix it with my limited skills.

Click to expand...

I did tear into the engine and something was broken off inside. I couldn't get the blade adapter off ----they are always too tough for me.

At this point I'm supposing that I'll swap another B&S engine into that Snapper mower.

If it's a quantum Model 12xxxx-xxx-xx A 799983 short block should work... i got one off of a member on here for $80 i think. Running great.
25MM or 7/8" crank... they're all over Ebay.