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jeeperaaron · Jan 21, 2009, 10:29 PM

I have a 17.5 briggs about 2 years old. I have read on here numerous posts regarding the vales. I may likely just need to adjust mine, but wanted to run all of my symptoms by someone and also hopefully verify int. and exh. Clearence. Mine misses and does crank hard. All of the electrical seems fine and the hard cranking seems compression related. Now one other thing I noticed was while idling in the garage it is back firing back through the carb and also an occasional exh back fire. Also I bought this mower second hand and noticed upon servicing it initially there was signs of dirt getting past the ait cleaner. I replaced the cleaner and greased the seating surfaces well to better prevent any contaminantes. The mower does not smoke any white smoke so I am hoping no deeper damage was caused by the dirt intrusion. Any thoughts?

jeeperaaron · Jan 23, 2009, 08:03 PM

Ok so I adjusted the valves to .004 int and .006 exh. This solved the hard cranking and they were out quite a bit. I still have a miss fire through carb and a back fire through exhaust. No one responded to my post so I though I might try at least giving an update. It has good compression (so it seems) so I can't imagine it's a burned or sticking valve. Any ideas on were to go next.

Any help would be greatly appreciated.

KISS · Jan 23, 2009, 09:11 PM

Where was the piston when you adjusted them?

jeeperaaron · Jan 23, 2009, 10:25 PM

About 1/4" aft tdc

KISS · Jan 23, 2009, 10:34 PM

There are two tdc's. Were you down from the power stroke or the intake stroke. You need to be down on the power stroke.

jeeperaaron · Jan 23, 2009, 10:37 PM

Thank you for the help! I was down on the power stroke. I ran it through intake comp power and exhaust a couple of times by hand before measuring aft tdc.

KISS · Jan 24, 2009, 04:19 AM

Did you by chance check the flywheel key? That will affect timing.

crigby · Jan 24, 2009, 05:53 PM

Hi,
Flywheel key is not an issue here! The fact that 120,000 engines with bad(improperly heat-treated) cams is the problem. Just a thought.
Try a warranty program.
Peace
Clarke

jeeperaaron · Jan 24, 2009, 10:22 PM

Thank you!

Would a cam problem be visisble. It looks as though there is a good amount of throw on the rockers. I just cleaned the carb again trying to determine if it is a lean condition. It is one of those emission carbs with a limited range of movement on the adjusting screw. I discovered that I can get the engine to smooth out some by choking it slightly. Have great fuel flow and the carb is spotless, I don't like the limited adjuxtment though. I will check into the warranty programs.

crigby · Jan 25, 2009, 11:28 AM

Hi,
Yes, a cam problem would be visible with the rocker arm cover removed. When turning the engine over, one rocker arm will have good travel and the other will have visibly less.
Peace,
Clarke