MTD Yardwork mower kick back , is flywheel key damaged ?

[naimc]

Hi my brother broke the balde off his Yardword mower MTD OEM I think.
I opened up the top head of the mower and inspected the piston and valves for damage. I found none so I just cleaned everything up removing all the carbon build up.
I did not adjust the vavles.

After cleaning the carburator I was able to start up the engine but noticed that it does kick back.

I tried starting it again and broke the pull cord and then tried to start it with a drill and experineced the same kick back.

I saw on YouTube videos that a broken flywheel key can cause the kick back.

Here is the sticker on the engine.its a 173 CC OHV made by MTD model : 6CZHS 173 FV ?
the model is :

The impact to the blade broke off the blade shaft adapter

Pictures of the flywheel and key

We can see a small gauge in the key channel . Is this flywheel done ?, causing the kick back or could it be cause by the fact I did not adjust the valves. ?

the key looks fine to me.

Mover with valve cover off.

My next corse of action should be to try and adjust the valves but I a not sure of what process I have have to follow. I do have some "feeler guages" for the valve adjustment.
I am I heading in the correct direction or id the flywheel damaged.

thanks for any suggestions

 

[gainestruk]

The only thing that concerns me it that grove on flywheel, I would buy a new key and make sure grove of flywheel and crankshaft line up perfectly, it doesn't take much to get it out of time.

 

[dougand3]

I agree - I bet you had a shifted key and a new key aligned perfectly will work. Wouldn't hurt to check valve clearances. Lots of youtube videos.

 

[naimc]

I will adjust the valves and cross my fingers that that tiny indent see on the left is not enough to throw the timming off.

I'll bring the flywheel and old key to local small engine repair place as I can't find much about this made in china MTD engine online. No parts, no manual etc.

Here is another shot of the indent, would trying to fill that with JB weld and sanding to original finish have a chance of working ?

 

[dougand3]

I wouldn't' do jb weld. I'd try at home first. Remember, the key is just for placement. It doesn't hold the FW - the super clean taper does. New key placed properly, ignore the "slice". Torque down good.

 

[naimc]

I reset the flywheel with the existing key as there is no obvious damage and I also adjusted the valves as spec on the mower .10mm intake, .15mm exhaust ( which works to to .004 inches intake, and .006 exhaust)

I tried to start the engine again using my drill with 1/4 to 1/2 dewalt adapter. no sign of on any starting but at the end of the cycle the engine snapped back and broke the adapter.

https://www.dewalt.com/products/acc...dy-14-hex-shank-to-12-socket-adaptor/dw2547ir

Specs say it can withsand 2,000 in. lbs. of torque. I have seen lots of people start mower engines with Drills on youtube, are they using a special socket ?

After this occured I did not bother to try starting with the pull cord as i have broken 2 already. When I turned the engine over, its seems to me that the compression was getting harder and harder on every 4th spin. I will get a compression tester to see what kind of presures are occuring during the kick back.

Can anything else be causing a kick back ? ( ie as timing belt inside the engine that could have jumped ? again not sure this engine has a belt)

 

[Scrubcadet10]

Usually the Crankshaft gear and camshaft are geared directly to each other, no belt or chain. Honda OHC engines use a belt.
I'm not sure if the gears could have skipped a tooth somehow...

 

[slomo]

Usually the Crankshaft gear and camshaft are geared directly to each other, no belt or chain. Honda OHC engines use a belt.
I'm not sure if the gears could have skipped a tooth somehow...

That is what I was thinking. Cam timing got off some how. Or the compression release if that engine has one? Might need to open her up and take a look.

slomo

 

[Scrubcadet10]

Yeah, could be the compression release

 

[Its Me]

Something was hit, blade should be bent or a good size nick unless it was a tree root, that leave not show of contact on the blade, I would say bent crankshaft, I made a unit to fix them in the engine that was 50 years ago and got the pattern from an old lawnmower shade mechanic, really he worked under a shade tree I learned so much from that old gentleman, when they do what your is doing and the sheared key I would say that is what it is, quick test, if you don't have a dial indicator put the blade back on, with the spark plug removed, carburetor facing up, mower tiled on its side and mark a place on the deck where one side of the blade is turn it 1/2 round and see where the other side is, think you will find that before you get there you will feel the resistance, I straighten several a season, most of the time the mower was loaded to a friend with tall grass that he left stuff in only to find it with the mower, I charge 50.00 unless it one like a Honda with all the self propel, brake blade clutch, that is 80, check the shaft before you do a bunch of work. I should work with that flywheel you have just hammer it up real tight, that is fine thread and can take the stress on the threads. I put a few pics, with the bent part facing down the upward pull is make and the long bolt is where the dial indicator it put to get to (0) reading