Running Issues After A Rebuild - Snowblower Forum : Snow Blower Forums
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post #1 of 13 Old 07-26-2015, 08:52 AM Thread Starter
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Running Issues After A Rebuild

My Briggs 8 HP was using a lot of oil so I replaced the rings, glaze-busted the cylinder, had a new exh guide pressed in, ground the valve seats and installed new valves. I adjusted valve clearance and put it back together. Now it won't build up much speed and backfires out the carb and exhaust. I put a used magnetron coil on it also. Any ideas what went wrong?
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post #2 of 13 Old 07-26-2015, 09:52 AM
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Did it do this immediately after rebuild? If so.
Hate to say it, but are you sure the timing marks are lined up,,,,correctly?
Easy would be a sheared flywheel key or forgetting to put it back in. I've never done either ( I'm not telling the truth).
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post #3 of 13 Old 07-26-2015, 08:40 PM Thread Starter
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The problems started right away. The flywheel key seemed a bit worn but its there. I felt confident the timing marks were correct but I'm feeling like maybe I need to look again. I did put a used magnetron coil on it. Is it possible for the coil to have an issue? It came off a non running engine.
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post #4 of 13 Old 07-27-2015, 10:11 AM
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I've never screwed up this bad
I'd start at the easiest, that "new" electronic piece sounds quick. If it checks out you have other points to search, those darn timing marks. Been there, done it.
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post #5 of 13 Old 07-27-2015, 01:23 PM
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you might just have to lean out the carburetor with the adjustment at the bottom of the bowl. sometimes when you rebuild an engine you may have to adjust the carb
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post #6 of 13 Old 07-27-2015, 08:47 PM
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You switched to a magnatron Ignition coil from the stock breaker points? Check the flywheel key and maybe even get a new flywheel key which is nice and snug so you know the timing is on. Other than it burning oil how did it run before the rebuild? The old Flo jet 2 piece updraft carburetors were prone to warping and the float bowel needle leaking on the old carburetor. Possibly try another carburetor to see if it runs better. As to buying a new carburetor that can get a bit expensive. Good luck.
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post #7 of 13 Old 08-06-2015, 11:05 PM Thread Starter
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It ran fine prior to the rebuild. And yes, I eliminated the points by putting on a magnatron coil.
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post #8 of 13 Old 08-07-2015, 06:31 PM
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I don't remember where I read the information, but I understand that it is possible to put certain Briggs coils on backwards and that could lead to your problems???? Have you done a leak down or compression test to insure that your valves are closing completely? Pulling the cylinder head and confirming both valves are closed when the piston is at top dead center or 1/4" past might help determine if the timing marks are off inside the engine block.

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post #9 of 13 Old 08-07-2015, 11:13 PM
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I would check the valve clearance. The valve lash is set at TDC is .011 exhaust and the intake is .007. You measure the clearance with a feeler gauge. It is also possible that your flywheel is not positioned properly since you mentioned that the flywheel key was loose in the slot it could have shifted, I would try a new key. The carburetor also could be contributing to this. Those Briggs Flojet updraft carbs were notorious for warping. However since it ran well before the rebuild I would say valves and flywheel key are the thing to check.

Last edited by GustoGuy; 08-07-2015 at 11:15 PM.
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post #10 of 13 Old 10-16-2015, 07:51 AM Thread Starter
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After taking a break from the project, I'm finally getting back to it. So far, I rechecked timing marks and they look good. The line on the crank gear lines up with the dot on the cam gear. Also, rechecked valve clearance and it's within specs
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