John Deere 826 snowblower with HM80 issues - Snowblower Forum : Snow Blower Forums
 
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post #1 of 10 Old 11-07-2016, 02:27 PM Thread Starter
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John Deere 826 snowblower with HM80 issues

I have a late 80's early 90's vintage Deere 826 snowblower with an HM80 engine.

I am having issues getting it to run smoothly. It misses at idle and backfires out the exhaust when coming down from full throttle. When it misses, you can hear a ting ting sound in the muffler.

I have replaced the solidstate coil, carb, plug. I have pulled the head and checked valve clearance (lapped valves as well) and cleaned the combustion chamber.

What can I check next? I looks like the muffler gasket need replacing but can that cause my issues? I have played around with the high and low speed setting on the carb but I still cannot get it to run smoothly.

I have good strong compression as well.

HELP!!!!
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post #2 of 10 Old 11-07-2016, 08:47 PM
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I suspect that it's either running super rich or the timing could be off due to a sheared flywheel key.

the carb presets are:
main jet: 1 1/2 turns out from lightly seated
idle jet: 1 turn out from lightly seated.


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post #3 of 10 Old 11-08-2016, 07:35 AM Thread Starter
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It is certainly possible I am rich. I will readjust the carb once the gasket comes for the muffler.

I did check the flywheel key and it is good.
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post #4 of 10 Old 11-09-2016, 12:37 AM
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If you were rich, you wouldn't be on here.
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post #5 of 10 Old 11-09-2016, 12:18 PM Thread Starter
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If you were rich, you wouldn't be on here.
Touche.
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post #6 of 10 Old 11-09-2016, 12:52 PM
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An exhaust leak will definitely cause the exhaust to pop while slowing down, and possibly at idle. The leak allows fresh air to be drawn in, mix with hot exhaust gas and burn off any unburned gasoline.

Back in the early days of auto emissions, engines with belt driven air pumps had diverter valves for this exact reason.
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post #7 of 10 Old 11-09-2016, 01:53 PM Thread Starter
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Quote:
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An exhaust leak will definitely cause the exhaust to pop while slowing down, and possibly at idle. The leak allows fresh air to be drawn in, mix with hot exhaust gas and burn off any unburned gasoline.

Back in the early days of auto emissions, engines with belt driven air pumps had diverter valves for this exact reason.
Good to know. I received the new exhaust gasket (this one is paper and the one on the engine is metal) yesterday. I will get that installed and try again tonight.
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post #8 of 10 Old 11-11-2016, 11:01 AM Thread Starter
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It looks like the exhaust gasket has helped a ton. I am still getting random afterfire coming off of full throttle but it not happened often so I consider this a completed project.

Thanks for the help everyone!
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post #9 of 10 Old 01-04-2017, 02:45 PM
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Nothing runs like a Deere.
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post #10 of 10 Old 01-04-2017, 03:46 PM
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If it even runs..
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