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crankshaft end play

S

Swagonmaster

Regular Contributor
Perhaps one of you guys that build 2 strokes regularly might offer an opinion, I am finally building my 1999 14 hp and the crank end play is only .002 which is a lot too tight, do I have to shim both the top and bottom end caps? I see that the shim kit for the bottom is hard to find and much more expensive than the kit for the top end cap. If I need to do both ends then fine but wondered because of the difference in supply availability of the kits.
 
I try to add an equal shim to both. If you can't, shim the bottom since the weight pulls the assembly down ward.

Jeff
 
Sounds as though it would be better to just shim both ends and be done with it since I have to order anyway.
Thanks for the advice, Bob
 
You shim so crank throw has equal play in both directions to keep rod/wrist pin as centered as possible...the crank rises during RPM increase and weight has nothing to do with it.
 
Pappy, what causes crankshaft to rise as rpm increases? Interesting statement. Certainly not questioning you that's it's not true, but explaination requested. You are one of my mentors here.
 
Note------The block is aluminum.----The crank is steel.------Co-efficient of expansion is double for aluminum.-----So block that is 20" long get longer by 0.000011" / inch / degree F.-------Or 20 X 0.000011 X 100 or so if temperature change is 100 degrees F.-----So parts are assembled and measured when cold.----Then a motor warms up and things change.
 
And, I'm taking a s.w.a.g. guess here, as the crankshaft tries to turn the driveshft it could ride up in the coupling.
Ok Pappy is anyone right?
 
And as I think about it, when the pinion gear is loaded the driveshaft will go up to the extent of the free play which will push the crank a touch.
 
That is quite possible but seeing how this one is laid out I thought it would be the case here. My shims have come in the mail, so it's time to get to work.
 
Had to stop and throw this in, it is probably the combination of all of the above. I've been totally blown away by articles on what is involved in high performance engine building and even though this is a stocker there are still a lot of forces flying around in a rotating hot mass of timed explosions that I for one tend to forget about. I am going to have a short moment of silence in sympathy for the engineers that have to keep track of all of this regularly.
 
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