HS40 piston arrow direction

ugmold

Active Member
#1
I picked up an HS40, had a split flywheel key. Replaced, hard pulling the rope, but started, sounded good, and stopped, another flywheel key split.

Took the engine apart and found the piston with an arrow pointing towards the valves.... I know my motorcycles pistons pointed forward, but my memory is pretty bad.

Which is correct?

Thanks
 

mustangfrank

Well-Known Member
#2
I picked up an HS40, had a split flywheel key. Replaced, hard pulling the rope, but started, sounded good, and stopped, another flywheel key split.

Took the engine apart and found the piston with an arrow pointing towards the valves.... I know my motorcycles pistons pointed forward, but my memory is pretty bad.

Which is correct?

Thanks
It is correct, arrow pointing toward the valves.
 
#3
I picked up an HS40, had a split flywheel key. Replaced, hard pulling the rope, but started, sounded good, and stopped, another flywheel key split.

Took the engine apart and found the piston with an arrow pointing towards the valves.... I know my motorcycles pistons pointed forward, but my memory is pretty bad.

Which is correct?

Thanks
"...hard pulling the rope..." You may want to check the valve lash. It could be that it is too wide. Also, something is funky if you keep shearing the flywheel key. Are you using a torque wrench and tightening it properly?
Michael
 
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ugmold

Active Member
#4
HS50 BTW.
Tore it down, tried the piston the wrong way...then back again to the arrow pointing towards the valves. Piston looks new-ish, rings look healthy. Piston ring end gap looks good. Journals are clean. With the crank out and the con rod attached there is no play, feels smooth. Wrist pin on con rod feels a little less than smooth, but I think ok.

Turns a bit hard (no cam) crank-rod-piston installed, there is also movement at the bottom of the stroke where the piston is at its lowest point but crank still turns before it makes the piston move again. Doesn't seem right.
++++++++
Michael, I used a key that fit snug. When you look up what it is supposed to look like you get a variety, one with a step, one with an offset. Not sure which one to use.

Thanks Frank, piston arrow now pointing at valves. Long side of con rod facing valves as well.
 

ugmold

Active Member
#5
I put the side cover on and rotation seemed a lot smoother so I buttoned things up. It now feels like it might be ok. Still don't know what key to use. The "exploded views" I see look like a straight key, no step or offset. I noticed the points cam had Tecumseh written on one side (inside) and on the other it is says top and has a little arrow that I am using to set the points, assuming that is correct. This runs flush to the keyway, so no key can slide under the points cover.
 

mustangfrank

Well-Known Member
#7
I found a stepped key and it did slip under the point cover..I'll give it a try if it pulls over ok.
Look up your engine with the full engine number, Parts Tree, Jack's wherever. Use the key listed, stepped keys will change timing slightly.

I agree with above, something is off, shouldn't be shearing keys. Check key fit in flywheel groove with it off the engine, any slack could cause it.
 
#8
Setting the spark timing requires a dial indicator measuring TDC and then setting the piston to .035” BTDC.
The flathead service manual has a good tutorial on timing an HS50

Edited To Add-
Actually I just realized that none if this is applicable unless you have a points ignition.
 
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ugmold

Active Member
#9
Frank. It's a Craftsman engine. I didn't think they listed them, I cross referenced the number to find out it was an HS50. You are right they do list them. Correct flywheel key is the "stepped" key. Thanks.

Massacre. No dial indicator here, I'm leaving the mag set where it is, looks like it has never budged, or been tampered with, I had it running and it sounded good previously. I just slapped it back together, fought to get a spark for hours (new points-condenser), got a weak one, still hard to pull start, will have to get back to it tomorrow. Thanks.
 
#11
I put the side cover on and rotation seemed a lot smoother so I buttoned things up. It now feels like it might be ok. Still don't know what key to use. The "exploded views" I see look like a straight key, no step or offset. I noticed the points cam had Tecumseh written on one side (inside) and on the other it is says top and has a little arrow that I am using to set the points, assuming that is correct. This runs flush to the keyway, so no key can slide under the points cover.
Did you lap the flywheel with some Clover and have a good look around? If any of the taper material around the key way is deformed, some could be proud of the taper. That would interfere with a proper fit. The taper fit can be easily overlooked, I’ve done it. I would break-out a blue sharpie and 400 or 600 clover, and my Optivisors.
 

ugmold

Active Member
#12
Did you lap the flywheel with some Clover and have a good look around? If any of the taper material around the key way is deformed, some could be proud of the taper. That would interfere with a proper fit. The taper fit can be easily overlooked, I’ve done it. I would break-out a blue sharpie and 400 or 600 clover, and my Optivisors.
Good idea SAT, I'll do that before I try starting it again.

Thanks Massacre. Going to Gomas?
 

ugmold

Active Member
#14
Tried starting this a.m. Gave a kick and heard a spin. Another key can only assume. I really think there is something internally wrong with this engine the way the piston stops at bottom dead center with play in the crank back and forth. All fits tight. Wrong rod? I have no idea about it's past. The rope being so hard to pull illustrates this, it shouldn't be that hard.
+++++
Massacre: No Swap Meet this year at Gomas.
 
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mustangfrank

Well-Known Member
#15
Tried starting this a.m. Gave a kick and heard a spin. Another key can only assume. I really think there is something internally wrong with this engine the way the piston stops at bottom dead center with play in the crank back and forth. All fits tight. Wrong rod? I have no idea about it's past. The rope being so hard to pull illustrates this, it shouldn't be that hard.
+++++
Massacre: No Swap Meet this year at Gomas.
Post up some pictures, including the model and serial.
 

ugmold

Active Member
#17
4:15 First evidence of sheared key
16:35 first run
20:00 2nd run after Oil change (metallic)

Part 2 of video (tear down) coming:

 

ugmold

Active Member
#18
Part 2
1:20 sheared key
7:00 engine resistance
8:20 a look at the piston
10:45 piston rings
15:18 ring end gap
17:08 WHAT I THINK THE PROBLEM IS

 
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