Engine surging?

[smstonypoint]

I have a 42" RER Snapper (circa 2001) with a two-cylinder B&S engine. The last time I mowed, the engine started surging when the mowing blades were not engaged, but sounded and acted normal when the blades were engaged.

Any ideas about the source of the problem?

Thanks in advance for any suggestions.

Steve

 

[oldnslo]

I have a 42" RER Snapper (circa 2001) with a two-cylinder B&S engine. The last time I mowed, the engine started surging when the mowing blades were not engaged, but sounded and acted normal when the blades were engaged.

Any ideas about the source of the problem?

Thanks in advance for any suggestions.

Steve

Steve,
since this is a twin cylinder I would suspect that one of the valves is slightly tight and causing the engine to run a little lean when under no load. Once under load the extra flywheel effect of the mower deck hides or masks this. It is also possibly that the idle jet is partially plugged in the carb and the two problems accent each other.

Can you do a compression test cold and then hot to see if there is any significant change. The valves grow in length when warm and may give an indication of which side to look at.

Roy

 

[smstonypoint]

Steve,
since this is a twin cylinder I would suspect that one of the valves is slightly tight and causing the engine to run a little lean when under no load. Once under load the extra flywheel effect of the mower deck hides or masks this. It is also possibly that the idle jet is partially plugged in the carb and the two problems accent each other.

Can you do a compression test cold and then hot to see if there is any significant change. The valves grow in length when warm and may give an indication of which side to look at.

Roy

Roy,

Thanks for the ideas. I don't have a compression tester, but your diagnosis sounds like the cure may be beyond my limited mechanical abilities.

Steve

 

[oldnslo]

Roy,

Thanks for the ideas. I don't have a compression tester, but your diagnosis sounds like the cure may be beyond my limited mechanical abilities.

Steve

Steve,
If manual choke, does choking it very slightly make a difference? If yes
Does the carb has any adjustments on it? If yes you could try adjusting it slightly richer to se if it helps any. Not sure what engine you have but it may be one of the "Sealed" EPA approved models that once the carb gets hair dirty or the compression changes slightly they start to lope.

Another option is to run some injector / carb cleaner through it. If your yard is a decent size where you burn the better part of a tank of fuel. Guess at the mixture and run some through it. Won't hurt and might help.

Roy

 

[smstonypoint]

Steve,
If manual choke, does choking it very slightly make a difference? If yes
Does the carb has any adjustments on it? If yes you could try adjusting it slightly richer to se if it helps any. Not sure what engine you have but it may be one of the "Sealed" EPA approved models that once the carb gets hair dirty or the compression changes slightly they start to lope.

Another option is to run some injector / carb cleaner through it. If your yard is a decent size where you burn the better part of a tank of fuel. Guess at the mixture and run some through it. Won't hurt and might help.

Roy

Roy,

The mower is at my farm and I won't be back up there until the 24th. I will certainly follow your suggestions. I had already bought some carb cleaner in advance of my next trip hoping that it might help.

The engine is a B&S V-Twin and my limited study of the carb indicated to me that it provided me with the opportunity to screw things up worse than they already were.

Thanks again for you help.

Steve

 

[Jim Thompson]

Actually, the carb on the B & S V- twins are relatively easy to disassemble for cleaning. They also seem to be more sensitive than most to dirt. I always put a good quality in-line filter on those after I clean them.

I think it would be money well spent for you to purchase the B & S repair manual for your engine. It has detailed and easy to understand instructions on rebuilding the carb and many other routine repairs- such as troubleshooting starter and charging system problems. It has loads of great info.
Jim