Author Topic: Hey guys. What do you think happened.  (Read 8958 times)

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chaddyg8

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Re: Hey guys. What do you think happened.
« Reply #30 on: February 19, 2018, 11:57:21 AM »
Crankshaft was not touched. Bought the sled. Replaced the crank seals , pistons and rings.. Also carb boots (artic cat). All new fuel line. And drove  it around a few times. Plugs looked good and it ran pretty good. First 2-3 mile trip at mid throttle there was a back fire and it stopped.

Mark Hill

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Re: Hey guys. What do you think happened.
« Reply #31 on: February 20, 2018, 12:24:35 AM »
 Notice the shine on the left edge of cylinder inyour pic , coolant leaks will leave a track like that and will cause detonation . Thinking pieces of the ring bent the electrode . Is there any damage inside the cylinder where the ring might’ve caught it and curious how your head looks .  Good Luck

mswyka

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Re: Hey guys. What do you think happened.
« Reply #32 on: February 20, 2018, 06:55:57 AM »
The part of the story that keeps my mind going back to an air leak is the part about the backfire.  From our experience there is a very close correlation between backfiring and air.  This thought conflicts me however since you say that the failed piston is on the PTO side of the engine which in essence has a double seal.  Most of our crank seal failures have been on the Mag side of the engine.  If there is oil left in the gear box then I would rule out crank seal failure. 

So the next place I would look is to the carb boot.  Did you use any sealant on the carb boot and carb spacer?  If so, what type?  And, is it still intact? 

There is a taper to the inside hole of the carb spacer.  Was the spacer installed with the taper in the correct orientation?

Then the last place that I would ever suspect is where the base of the cylinder seals to the crankcase.  Are these mating surfaces clean and flat?  Did you use any sealer on the gaskets?
Intruders:  1978, 1979, 1981 Custom (Pink)
Invaders:   1980 440
Projects:    1981 Invader 440

chaddyg8

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Re: Hey guys. What do you think happened.
« Reply #33 on: February 20, 2018, 08:28:16 AM »
mswyak.  The backfire also baffles me. It never backfired before? I prob did 20 small trips around the house just taking it easy prob 2-4 miles 10-30 min trips. This was the first (longer) trip and it was not at full throttle but moving right along and then boom! Backfired once and Stumbled. Then started running bad and died.  I did use sealant on the carb boots and all other Surfaces was moto-seal.

kawhead

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Re: Hey guys. What do you think happened.
« Reply #34 on: February 20, 2018, 08:40:36 AM »
back fire was from the final lean out as the piston failed.....

gixxer6

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Re: Hey guys. What do you think happened.
« Reply #35 on: February 20, 2018, 09:27:49 AM »
I've heard that final sound before.   :'(

chaddyg8

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Re: Hey guys. What do you think happened.
« Reply #36 on: February 20, 2018, 09:33:58 AM »
 I appreciate the responses guys!  When I got the sled it didn’t have a fuel pump.  So I bought a new Mikuni duel feed. I’ve never seen air in the lines but could that have caused this?  My biggest thing is I’m not putting this back together and getting the same result! So it’s goin together really slow. Lol. Thanks again.

Doug in NY

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Re: Hey guys. What do you think happened.
« Reply #37 on: February 20, 2018, 11:14:20 AM »
I believe a good test after a re seal job is a leak down test. I was surprised on the last 440 I re sealed, the carb spacers kept leaking even with the use of a sealer. I took the spacers to a shop and had them flat lapped. Then the engine passed my test of 6 lbs. for 6 minutes. :)

kawhead

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Re: Hey guys. What do you think happened.
« Reply #38 on: February 21, 2018, 11:06:18 AM »
I also have heard that sound.....and worse

sprocket

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Re: Hey guys. What do you think happened.
« Reply #39 on: February 22, 2018, 06:51:45 AM »
Check your stator make sure you have 18 ohms & I seal everything with yamabond on most of my gaskets including my carb boots