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I have been through several issues with my Mower this year-- I recently rebuilt the carb and now have had to replace the #2 cylinder head. A new issue has developed that I was hoping the get some input on. The engine is a Briggs and Stratton 44L777-0015-B1 23 HP. After completing the cylinder head install I was able to get the mower up and running. However it surges at full speed, runs fine at idle, and the surge largely disappear with PTO engaged. I was able to mow my entire 6 acre lot and other than a couple of small backfires during the process had no other issues. When shutting down it ran a little better, but the surge was still there. Any ideas?

Need to clean the main jet in the carb and check the float needle valve. If you didn't replace it when you first cleaned the carb, will need to do it now.

Rivets said:

Need to clean the main jet in the carb and check the float needle valve. If you didn't replace it when you first cleaned the carb, will need to do it now.

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The float needle was replaced, but there are two jets in this particular carb. If they were reversed, could that produce this issue?

Yes it could. These carbs have a tendency of driving mechanics nuts as they are more like two barrel auto carbs, which many have not worked on. Sounds like you carb is running rich, which can be caused by a few things if not check during rebuilding. First is float height, which is very critical as you are feeding two cylinders using "two carbs". Fuel transfer tube not seated properly causing an internal leak. Bad gasket. Attached a service manual, if you don't already have one. Good luck.

http://dl.dropbox.com/u/12502267/B&S Service Manuals/05_273521TwinCylinderOHV.pdf

Thanks for the input and the manual. I will recheck the carb at this point.

Another possibility is a leaking intake manifold. I have a 21hp Craftsman acting up in a similar way. When I recently replaced the carb recently I noticed the manifold was warped. It still surged and backfired so I sealed it with a little silicone and it ran great, for a couple hours. I ordered a new manifold, I'm sure that is my problem. Just another idea.

Carvel Loafer said:

Another possibility is a leaking intake manifold. I have a 21hp Craftsman acting up in a similar way. When I recently replaced the carb recently I noticed the manifold was warped. It still surged and backfired so I sealed it with a little silicone and it ran great, for a couple hours. I ordered a new manifold, I'm sure that is my problem. Just another idea.

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Thanks for the input.