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Discussion Starter #1
The engine numbers are 287707 0220 01 9309094A. It overheated and seized. When I took it apart as soon as I loosened the rod cap it spun freely. The crank wasn't hurt and the rod just had a little problem. The machine shop polished the crank, resized the rod, honed the cylinder, and did a valve job.

I put it together, all clearences are right and it spins fine. I set the valves at .003 intake and.008 exhaust. When I tried to start it, it backfired through the carb hard enough to sheere the flywheel key. Figuring I did something wrong I pulled the engine back out and pulled the bottom cover off. The timing marks are kinda hard to mess up with but I checked them anyway.

Put everything back together with a new flywheel key and it started and ran real nice. I let it rub for about 15 minutes and ran it at all throttle levels. I shut it off and when I tried to restart it again it backfired again and sheered the flywheel key.

The only thing I noticed that I'm not sure about is when the intake valve closes it then bumps open again right away maybe .040 or .050. Since the ignition module is going the fire everytime the crankshaft makes a revolution it's non compression stroke firing happens during the time the intake valve is doing this little secondary bump after it closes. Does this have anything to do with the compression release?

I am totally confused by this one, HELP PLEASE.
 

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That is the compression release operating, but you should not have spark at that time, unless of course, the flywheel key is partially sheared. I assume you are using the correct key, not one of the old style with convex corners. Be sure the belleville washer under the flywheel nut is installed correctly. Also, be sure the taper on the crankshaft and flywheel is clean and dry.
 

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Are you sure you are torquing the flywheel nut to the proper spec.? If it's not tight enough it will cause it to keep shearing the key. Also like rscurtis states... Make sure the taper is clean and dry..
 

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Discussion Starter #4
Thanks for the ideas. I did notice that on the parts breakdown they don't show the flywheel bolt like the one on this engine. The flywheel sits sits .5 inches over the end of the crankshaft. I thought that looked kinda strange but the engine has not been apart before and the starter gear aligns with the ring gear ok. The match up for the taper seems ok as well.
 

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Whatever flywheel key used make no difference. The flywheel keys ONLY duty it to hold the flywheel in alignment with the crankshaft keyway UNTIL the nut or bolt is torqued to proper torque. Obviously flywheel is not being properly torqued OR crankshaft or flywheel tapper has oil or dirt on them. That is the entire problem.

Walt Conner
 

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Discussion Starter #6
Without the key installed, the flywheel seems to spin on the crankshaft very easy. Shouldn't there be some resistance just pushing down on the flywheel? The crankshaft end and the flywheel seem to be very clean. Would you suggest spraying with brake cleaner or maybe even a light scuff with find emery cloth? The fit seems good and both pieces look like they are polished.
 

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"Shouldn't there be some resistance just pushing down on the flywheel?"

The tapper of the crankshaft and flywheel bore should jam just the same as a morris tapper does on a drill press or lathe. I have never experienced it but some say they take fine valve lapping compound and lap the two together to fit. Of course, all this has to be very, very cleaned off afterward. You must have some sort of contamination there.

I think you are missing something.

Walt Conner
 

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Discussion Starter #8
I keep thinking I've missed something, but can't for the life of me figure out what. After the flywheel bolt is torqued it seems like it fits nice and tight. I got a pretty good snap when the flywheel released from the crankshaft.

I think tomorrow I will look real close at that fit, clean the parts well and try it again.

Thanks for the ideas.
 

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Discussion Starter #9
For those who helped out with my problem, I took some fine grit emery cloth the the flywheel and crank end and put it back together. I put a little more torqe on it then the specs call for and sent it on it way running fine. The customer called me in the morning and said it sputtered, backfired a little and died again.

Just knowng my fix didn't work, I tore it apart again. Much to my surprise the key was fine. At least that held. Now I have to look at what is making it quit when it gets hot.

Thanks for the crankshaft fit idea.
 

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CalifornianGravelynator
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4,330 Posts
sorry to hear it dont work right. good luck
 
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