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Old 01-08-2013, 09:00 PM   post #1 of 13
Shoey
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Default Craftsman Snowblower Surging/Hunting & Running Rough

I am working Craftsman 536.887990 Snowblower. It has a Sears (Tecumseh) engine 143.029003. It starts easily with one push of the primer and one good pull on the starter rope but quickly begins to surge. Turning the choke back to partially on makes the surging less extreme but still very noticeable. It won't idle very slow without dying. I cleaned the carburetor and it still didn't work so I bought the rebuild kit and replaced even the welch plugs to no avail. I even tried a known good carburetor and it still surges like it did before. It has fresh gas with Stabil in it and I have tried several different sparkplugs. I have tried to hold the governor rod while it was running and it didn't surge as much but instead sputtered and died. Took the muffler off, it is not clogged. This snowblower is only a few years old so I wouldn't suspect any valve problems or the engine to be filled with carbon deposits. Any ideas? Thanks in advance.
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Old 01-08-2013, 09:07 PM   post #2 of 13
greenbud21
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

If the fly wheel is easy to met to its always a good idea to check the rust has not built up in the ignition coil. See this alot in the spring on lawn tractor up north here
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Old 01-08-2013, 10:47 PM   post #3 of 13
mla2ofus
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

Sounds like an intake valve sticking enough so it's not quite seating completely.
Mike
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Old 01-09-2013, 07:30 PM   post #4 of 13
THH2079
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

Some of that is normal, I have a 6 year old Techumseh 8HP that does that till you put it under load. Then it runs great and throws snow to the neighbors house 50 feet away. I've seen posts on here and other places that have said that that is just normal operation of that particular year of machine.
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Old 01-09-2013, 08:43 PM   post #5 of 13
Shoey
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

Thanks for all of the advice. I am starting to think that the problem is with the valves also. I thought maybe the surging was just a part of normal operation and poor design too, but the surging just started recently and I think it is too severe to be normal because I can't idle the engine much less than full throttle without it dying. I guess I will be taking a look at the valves and while I'm at it, the flywheel for rust. Any other thoughts?
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Old 01-09-2013, 09:03 PM   post #6 of 13
mikeinri
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

Are you getting good fuel flow to the carb? Is the tank clean inside, is there a screen (and is it plugged)? Is there a fuel cutoff valve, and it is opening properly and unobstructed from debris? Is there a fuel filter, and is it clean? Are the fuel lines clean and not shedding inside?

Just thinking of simple things before you rip it open.

Mike
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Old 01-10-2013, 04:27 PM   post #7 of 13
THH2079
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

I also had a snowblower I worked on last year that would idle fine, but when you tried to put it under load, any load, it would die. I pulled my hair out over that one and did internet research like crazy. Finally opened up the head, cleaned all the crap off the valves, relaped and adjusted the valve clearances and it worked splendid. Take the time to clean up the head and put on a new gasket while your at it.
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Old 01-10-2013, 06:51 PM   post #8 of 13
Shoey
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

Sounds like a plan. I will check out all of those things. Thanks again for the advice.
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Old 01-12-2013, 03:39 PM   post #9 of 13
Shoey
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

I opened up the engine and found that the valves had no clearance. I ground the valves shorter so that there was a proper clearance. I also cleaned them and the cylinder head and replaced the cylinder head gasket. It still surges and I think it may run even worse than before. I think I will just have to put it back together and give it back to the guy.
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Old 01-12-2013, 05:17 PM   post #10 of 13
THH2079
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

Did you lap the valves? Tighten head bolts to spec? Fine tune carb now that you played with the innards?

Just some additional suggestions. When I did mine I cleaned all the gunk off the valves, lapped them, ground them and adjusted for proper clearance then put it all back together with new gaskets and torqued the head for proper tightness and did a final carb adjustment.

Good Luck!

Todd
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Old 01-12-2013, 05:46 PM   post #11 of 13
rscurtis
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

Most likely, the idle circuit in the carb. is clogged. The fact that it responds to partial choking vindicates the valves or ignition system. This is a very common snowblower ailment.
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Old 01-13-2013, 04:39 PM   post #12 of 13
Shoey
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

I did not lap the valves but I did thoroughly clean the valves and seats. I tightened the head bolts to spec. I did find a replacement motor for the guy's snow blower but I am keeping the old engine and would like to get it working. One thing I didn't look at was to see if the flywheel key was sheared. I wouldn't think to check that on a snow blower since sheared keys seem more like a lawnmower thing, but I will look at that anyways. I am a little suspicious of the exhaust valve as it looks like it is not seating on the correct part of the valve. It is seating more on the non angled part so that may be the problem too.
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Old 01-19-2013, 02:53 PM   post #13 of 13
Shoey
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Default Re: Craftsman Snowblower Surging/Hunting & Running Rough

Woo! It is finally running! Culprit: not enough gas in the tank. For testing purposes, I only filled the tank just so the bottom was covered, I decided to fill up the tank about 1/3 of the way and started it, adjusted the carb and now it runs like a dream. It must have good compression and a heavy flywheel because I was able to get it to idle at like 600 rpm. Amazing! Thanks for all your help!
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