Engine Snapper Rear Engine-Motor revs up and down

[jimcahoe]

My mower revs up and down even at full idle. The plug also has a lot of carbon build up. When cleaned it comes back quick.

There is some smoke coming out around where the muffler is mounted sometime. The oil is full. Mower doesn't appear to use any oil.

Does anyone have any suggestions.

It is an SX825.

 

[mechanic mark]

250816BE SNAPPER REAR ENGINE RIDING MOWER Manual | SearsPartsDirect

 

[turbofiat124]

My mower revs up and down even at full idle. The plug also has a lot of carbon build up. When cleaned it comes back quick.

There is some smoke coming out around where the muffler is mounted sometime. The oil is full. Mower doesn't appear to use any oil.

Does anyone have any suggestions.

It is an SX825.

I was told by a small engine mechanic that an engine reving up and down is a sign that the throttle shaft is worn and is sucking in air around the throttle shaft seals. The reason it speeds up and down is due to the governor kicking in trying to maintain a constant speed.

Don't know about the carbon buildup on the plug.

As a matter of fact, my old 79 Snapper as a Tech. 8hp that did this before I pulled the deck off to put on my 2000 model. But when I engaged the blade to put a load on the engine it smoothed out. No big deal, just sounded like crap.

 

[mechanic mark]

Post snapper model & serial numbers as well as all numbers from engine and engine manufacturer. If B&S engine: model xxxxxx, type xxxx, trim xx.

 

[jimcahoe]

Post snapper model & serial numbers as well as all numbers from engine and engine manufacturer. If B&S engine: model xxxxxx, type xxxx, trim xx.

model 195707 type 016101 code 970224yd

 

[SeniorCitizen]

Remove the carb. float to check for internal gas and make sure the muffler heat shield is in place.