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Discussion Starter #1
Hi

I was given a 2011 platinum 30 (model 921018) that would not start.
Engine is B & S OHV 342cc.(model 21m314 type 2121f1)

Electric starter was missing and pull cord did not work.Fixed the recoil starter
but engine was turning over hard enough to damage cheap recoil mechanism.
Removed valve cover and found bent push rods.After removing head found exhaust valve guide had slid out of place.Also the lower part of the intake valve was blueish... sign of overheating?? To make a long story short I pressed the guide in place lapped valves and installed head with new push rods and head gasket.

Engine started right up ,I removed a few drifts of snow in the drive and when I dropped the throttle to idle speed the engine backfired and stopped.It would not start.

Apparently this is common with this engine.The the valve guide was out of place again and exhaust push rod bent.

Has any one had this problem and would a new or good used head with tight valve guides solve the problem? The backfiring problem should not push out a valve guide if the head has not overheated.

Thanks...Flattop
 

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Hmm, maybe a good candidate for a $300 Predator? Sounds like something is up with that engine. Possible to fix, but how much money are you going to spend hoping the next thing fixes it?

Are the valves overheating and expanding and jamming in the guides?

Are those guides supposed to be peened in place? I think on some you are suppose to take a punch and put a little dent in both ends to hold them in.
 

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did you check the head and block to make sure they are plane? head or block tha isnt true would most efinately be a sign of overheating.. resolving this should resolve the warping issue.. warped heads or block needs to be either planed by a machine shop or changed out

maybe a repower would be easier on the wallet??
 

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Discussion Starter #5
I checked the head and it is not warped.I called the guy who gave it to me .He says he gave it a hard time but after it backfired an stopped it still turned over but would not start so I assumed the engine did not stick but could have overheated since the intake valve stem is blue at the base .The valve stems are not scored.These engines run lean and hot to meet EPA standards and backfire unless you slow them down slowly, tend to backfire. But this should not damage engine.A new head is expensive with the low Canadian dollar but a good used one is feasible .The rest of the sno-thro is like new.
 

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tap the guide back in then put some lapping compound on the exhaust valve stem n run it in the guide bore. the blued stem tells me it getting tight in the guide. fatten up the carb a bit to drop operating temp,
 
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