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Garden Tractors / Mowers / Scooters Vintage lawn and garden tractors, mowers, snow blowers, snowmobiles and other old machinery that is driven by small air cooled engines.

Garden Tractors / Mowers / Scooters

B&S cam timing issue


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  #1  
Old 06-09-2009, 06:19:57 PM
Ramz Ramz is offline
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Smile B&S cam timing issue

I have an old Lawn Flite mower with a 400cc Briggs and Stratton 11hp motor (model 252707). It threw a rod so I decided to try and see if I could fix it (first time with one of these things apart). To make a long story short, I have it all back together with the new rod and it will not start (doesn't even backfire or anything). It turns over fine, has good compression, has lots of fire at the spark plug and both of the valves are making a good seat when closed. When turning the motor over with the plug out, it tends to spray a fair amount of fuel out of the carb however I am not getting any fuel coming out of the spark plug hole. (perhaps something happened to the carb during the repair process?) All of the internals appear to be fine upon inspection and the flywheel is installed properly with the key in place.

However I do wonder if I timed the cam correctly because the cam shaft gear in that motor has 2 marks. One mark is a dimple on the outer edge of the cam shaft gear (which, from my research, would be the mark that is used to time the cam shaft) however it also has a second mark in the form of a hole. (see drawing) I know the crank shaft gear isn't an issue as it is keyed to the crank. When I put it back together I aligned the crank shaft gear to the hole on the cam shaft gear (not the dimple) because when turning over the motor while observing the valves (with the head off of course), it appeared to make sense...being a 4 stroke engine and all. I am going to take the engine apart again and try and fix the problem however I would like to get some advice from you seasoned pro's out there who can pretty much troubleshoot these things in your sleep! : ) I hope that it is a simple of "your an idiot...line up the crank shaft gear with the dimple on the cam gear". I tried lining it up with the dimple and the timing of the valve movements didn't seem to make sense. Any and all help would be appreciated.

Thanks.

Mark.
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  #2  
Old 06-09-2009, 06:52:33 PM
Sky
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Default Re: B&S cam timing issue

Line the dimple with the dot on the crank tooth. It'l make sence when it's running.
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Old 06-09-2009, 09:44:57 PM
Ramz Ramz is offline
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Default Re: B&S cam timing issue

Any idea what the hole in the cam gear is for? balance perhaps?
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Old 06-09-2009, 11:51:24 PM
Sky
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Default Re: B&S cam timing issue

That hole is for when they turn the cam on the Hobb machine to cut the teeth at the factory.
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