MS201t not turning thru bottom dead center.

[67L36Driver]

I have three from a landscaper I’m rebuilding.

Aftermarket top ends.

On assembly I found that they wouldn’t turn past BDC. WTF !!

At first I thought it was piston skirt length but after measuring with dial calipers I could find no significant difference between the OEM and aftermarket piston. .003-.005 at the most lengthwise.

Then I see marks where the crank counterweights touch the transfer port ‘spigot’.

So I ground some clearance. And then ground more clearance.

Actually ground a gob of clearance. [emoji2960]

Stihl no joy.

Anyone else run into a problem like this?

 

[67L36Driver]

Assembled piston, cylinder, wrist pin and bearing on the crankcase. Spun it over using my impact wrench on the clutch hub.

Now we can see where the interference lies.

Both sides.

One doesn’t expect something like this. [emoji43]‍[emoji94]

Dremeled a bunch of clearance and we are good. [emoji106]

 

[Hinerman]

@Lone Wolf

 

[Ketchup]

What aftermarket brand?

 

[67L36Driver]

What aftermarket brand?

IDK, white box.

 

[67L36Driver]

So, we had two problems actually. Counterweights hitting the underside of the piston and the transfer port ‘spigot’.

 

[smokey7]

Oem crank and case? Probably clears the stuff they make since they make everything to use less material.

 

[67L36Driver]

Oem crank and case? Probably clears the stuff they make since they make everything to use less material.

They ? Who is they?

Painfully apparent is Stihl designed an absolute minimum crankcase volume at BDC in order it maximize the air/fuel charge going to the combustion chamber.

If any of the bearings get sloppy there will be collateral damage.

 

[smokey7]

They= aftermarket suppliers. Especially the economy cheap white box stuff online. I hope im not pissing you off. Just my observation.