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Discussion Starter #1
I'm hoping someone can give me an idea of what I can look at to get this thing running. This may be a long post, but I'm trying to give as much info as possible.

Third mowing of last season, blew the engine in my Husqvarna YTH18542 so I bought an old Troy Built with the same engine to do a swap. I decided to park the Husqvarna and just do the swap before this season. I used the Troy Bilt for the rest of last season and it ran fine, except for the last time when I had a little trouble starting it (had to turn the key 3 or 4 times before it would finally "catch" and start). Fast forward to today. Got everything hooked up and hit the key. It turned over about two times and as I was reaching for the throttle control to put the choke on, it started. It was running at an idle though as I soon realized that I forgot to hook up the throttle cable. Shut it off and hooked up the throttle cable. Hit the key again and it fired right up. Ran it on high speed for probably 20 or 30 seconds and dropped it back to low speed for about the same amount of time and then back to high speed. Ran smooth in both positions. Shut it off and restarted it two or three times. (Happy dance begins) Pulled the deck outside to start cleaning it in preparation for installation. About that time my wife gets home and asks how it's going. I smile and hit the key and it fires up, runs for about three or four seconds and then the RPM's start to drop. BOOM, loud backfire through the exhaust (sounded like I shot my .44 inside the shop). (Happy dance stops, smile goes away.) I hit the key again and it starts backfiring though the exhaust. Wife looks at me funny, shrugs and goes in the house. I figured one of the valve locks may have loosened so I popped the valve cover. Bought a new set of feeler gauges since my old ones were in pretty bad shape. Readjusted the valves and put the valve cover back on. Now it turns over, but nothing - no backfire, no start. I pulled the fuel line off the carb and hit the key. As long as it shouldn't squirt fuel out like an automotive fuel pump, it appears that the fuel pump is working. Took off the breather and let it pump a little fuel into the inlet. When I did that as I turned the engine over, it was spraying some of the fuel back at me. Put my hand over the inlet and cranked it and it literally sucked my hand onto the opening. I check, and it is getting a spark as well. No gas (flooding) smell.

Details of the swap:
Original engine - B/S Intek 31Q777
Donor engine - B/S Intek 31P777
Original engine used a fuel pump, but the donor was a gravity feed so I swapped the fuel pump from the original.
Carb is the one that was on the donor engine.
Original engine used a higher amp alternator than the donor, so I swapped the flywheel and alternator from the original to the donor.
Original used a voltage regulator, but the donor did not so I installed the regulator on the donor (plus the alternator wiring was different).
Changed oil and filter, new plug and new air filter and pre-filter.
As mentioned above, adjusted valves - Intake - .003, Exhaust - .006

Any help or ideas would be greatly appreciated! I really need to mow (lost one of the dogs for about an hour yesterday).
 

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First thing i would check since you changed flywheel is the flywheel key, sounds as if key sheared or is/was damaged causing flywheel to move and throw timing off............

hope this helps!!! and good luck getting it running again!!!
 

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Discussion Starter #4
I may be able to answer my own question. I used the keyway that was still in the flywheel which came from the original engine. Is it possible that it was weakened due to abrupt stop the engine made when it seized? Also, could it be improper torque on the bolt? I couldn't figure out a way to keep the flywheel from turning while I torqued it down so I just hit it pretty good with my 1/2" impact.
 

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Impact could have done it in.
On the bottom end of the crank is the drive pulley. I've put a belt around it (while holding up my pants) to loosen and tighten the flywheel nut.
You might have just solved a similiar problem for me, that I'm having with a Kohler engine.
 

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Best way to stop the engine from rotating is to remove a spark plug, rotate the engine to lower the piston, then stuff some rope in the hole.
 

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Best way to stop the engine from rotating is to remove a spark plug, rotate the engine to lower the piston, then stuff some rope in the hole.
I've heard that one before but can you bend a valve doing that?
 

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You have to rememeber too, the key is mainly for alignment not for driving from. If the taper is rusty or for some reason doesn't fully seat together the key will eventually shear.
Whenever I take one apart, I put a bit of lapping compound between the two and make sure to clean them up. Just make sure you get all the compound off.....Mike
 

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:howdy: Ditto on what mike stated. I lap every flywheel that I remove. On some of our go-kart racing engines we do not run a key, we just lap the flywheel end.
 

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Discussion Starter #13
Just want to say thanks to everyone for their help. Took a lot of work to get the flywheel off. Finally got it to free up by using my two bolt puller (cranked down) and popping both sides of the flywheel at the same time with a 4lb. sledge in each hand. Removed what was left of the keyway. Cleaned and lapped the flywheel and crank (surprised my lapping compound was still good after about twenty years), installed new key and torqued it down (rope trick in the cylinder bore worked great). Put it all back together and it fired right up. Finished cleaning the deck. Installed new blades. Put the deck back on and adjusted it. Just as I hung the hood back on I hear this sound. I turn around and look out the shop door and it's freakin pouring! So much for mowing today.
 

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Discussion Starter #14
Just want to say thanks to everyone for their help. Took a lot of work to get the flywheel off. Finally got it to free up by using my two bolt puller (cranked down) and popping both sides of the flywheel at the same time with a 4lb. sledge in each hand. Removed what was left of the keyway. Cleaned and lapped the flywheel and crank (surprised my lapping compound was still good after about twenty years), installed new key and torqued it down (rope trick in the cylinder bore worked great). Put it all back together and it fired right up. Finished cleaning the deck. Installed new blades. Put the deck back on and adjusted it. Just as I hung the hood back on I hear this sound. I turn around and look out the shop door and it's freakin pouring! So much for mowing today.
 

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:howdy: Job well done. glad to hear you got it going. Every time I turn around its raining up here in NE IN, I am going to have to buy a cow/goat to get the grass mowed. Ground is like a sponge.
 
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