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2017/06/12 15:35:12

jerry.hawkins0

10 year old B & S 22 HP V-Twin

I have a B&S 22HP V-Twin engine that just started running rough. It has a really loud popping noise at higher RPMs and backfires up through the carb. How do I diagnose the issue?

16 comments Leave a comment

Mikel1

Are both cylinders working? Only one cylinder running will make it run rough.
Backfiring thru carb could be timing issue or valve issue.

2017/06/12 16:05:37

jerry.hawkins0

My father-in-law was a mechanic and believes it is in the R cylinder. He didn't have a compression tester with him but believes the compression is low. He thought there was oil on the plug. I didn't see it. I can check for spark. How else do I see if both cylinders are running?

2017/06/12 16:16:36

Mikel1

You can start it up and unplug spark plug boot from 1 cylinder then repeat for other cylinder. If it dies then check that cylinder that's not running.

2017/06/12 16:54:27

jerry.hawkins0

BTW Thanks for your quick responses!

The engine stopped when I pulled the right cylinder plug wire. It kept running with the left one off. I have spark at the plug wire and have tried several different spark plugs. Is it likely a valve on the left cylinder? I can pull the cover tonight to see if it appears to be working.

2017/06/13 17:10:45

Mikel1

Yeah I would pull the valve cover and check it out. Also check valve operation and valve travel.

2017/06/13 19:17:39

jerry.hawkins0

The push rod was loose and I pulled it out. It was bent. I straightened it and put it back in. Put the cover on and started it up. Still loud and popping some. I shut it off and took the cover off. The rod was again loose and bent. I was afraid that might happen that is why I didn't want to put a new one in until I was sure it would be ok. Does that mean a stuck valve or something terminal or ??? What do I do next?

2017/06/14 20:39:27

Mikel1

Sticking valve, valve guide moving, loose valve seat. I would make sure rocker arm studs are tight and check valve guide heights. If no problems there then your going to have to pull the head off. Is this the intake valve pushrod?

2017/06/14 21:53:20

jbrobinson33

I've got a similar problem with my V-Twin 22. Was running rough under load even though spark testers were showing fire to both cylinders. Pulling plug wires one at a time, I determined the left cylinder was not working - even though it's getting fire to the plug. The push rods are brand new, I just replaced them last week and they are still straight. (I had to replace one last year because the motor apparently ate it, so I replaced them both this year just for good measure.) Valves move when I turn the motor. I'm not sure how to check the valve adjustments like you suggest - is there somewhere I can find a how-to guide on doing that.

2017/06/15 18:15:38

Mikel1

jbrobinson33
I've got a similar problem with my V-Twin 22. Was running rough under load even though spark testers were showing fire to both cylinders. Pulling plug wires one at a time, I determined the left cylinder was not working - even though it's getting fire to the plug. The push rods are brand new, I just replaced them last week and they are still straight. (I had to replace one last year because the motor apparently ate it, so I replaced them both this year just for good measure.) Valves move when I turn the motor. I'm not sure how to check the valve adjustments like you suggest - is there somewhere I can find a how-to guide on doing that.

Have you tried another spark plug? What valve adjustments are you referring to?

2017/06/15 19:30:10

jbrobinson33

I swapped plugs from one side to the other. The good side fired up and ran just fine. The bad side fired up and ran really rough, slowed down, and then died. So both plugs are good - but only one cylinder runs properly.

I was just assuming the valve s or rockers needed adjustment, but I've delved into that kind of "mechanicing"- do you have another theory?

2017/06/15 21:11:39

jbrobinson33

*NEVER delved into that

2017/06/15 21:31:07

Mikel1

Not hard to adjust the valve clearances, probably some YouTube videos on it.
I would check valve clearances are to spec and then check the valves travel or lift.

2017/06/15 23:33:45

jbrobinson33

Adjusting the valves got the cylinder working!

It still bogs down a little bit and runs a little rough under load when mowing but NOTHING like it did before when it was running on one cylinder. Guess I just need to do a little fine tuning on it now.

Thanks for the help - much obliged.

2017/06/16 11:32:28

Mikel1

I do wonder what the compression is on both cylinders. A leak down tester is handy to ensure valves are not leaking.

2017/06/16 13:10:52

jbrobinson33

Are the inexpensive ones on ebay or Harbor Freight ($20) any good or do you have to spend more to get one that actually works?

2017/06/16 16:22:20

Mikel1

A regular compression tester doesn't cost much. However with the compression relief it can sometimes skew results. However you can still get an idea on compression.
A leak down tester needs an air compressor and cost more. Also have to make sure flywheel doesn't move, air pressure can move it. Not really practical to buy if only using it a few times. It does narrow the problem down faster though.
Easier just to check valve operation then pull the head to see if the valves are sealing. New head gasket doesn't cost much. Then if there is still a compression problem then you will have to dive deeper.

2017/06/16 23:47:47

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10 year old B & S 22 HP V-Twin

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