Stihl ts400 take 2

rusty.western.flyer

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I have no idea what to look for, but need a new crank case for the saw hybrid saw engine. Prices are all over the place.

Think I might have time to break it down today, would also like recommendations for bearings.

Was lazy and didn't take the jug off to press a metal carb tube on it and pulled the head bolts. I now have a Bridgeport, so want to start with a new case and weld/drill it proper.

Started with a CG, stuck a ts400 jug on it with a spacer for squish. It has the correct sized wrist pin bearing, but the jug holes have a tighter pattern. Thought I was being slick, so filled the stock holes with aluminum screws, then re-drilled the head bolt pattern. Well, the holes overlap ever so slightly, should have welded the plugs in, which will be done this time. I balanced the crank with the new jug before assembly, so would rather just transfer to a new case.

A video of it running before I screwed it up.

 

ImpulseRocket89

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Why not simply remove the jug, clean things up, put in a stud or long bolt into the holes for the jug that you drilled and tapped to protect them, and then weld the filler bolts? Might require a bit of light machining to flatten the flange out again, but that would give you better retention of said filler bolts. Then just chase the holes out with a tap to ensure they are good to go.
 

rusty.western.flyer

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If I did it again, I would fill the 8mm threaded holes with aluminum bolts, chop off slightly short, then cap with a TIG fillet.

Last time, threaded ally bolts, staked them, then faced with a file. Set the jug/piston on, centered everything and used a center punch to mark the case halves. Setup in pillar drill, and used the same pattern as the saw. Two holes overlap about 60%. Thread are now trashed and would like to start over. It's going to be more labor to save this case than to buy new.

As an added benefit, I can change the main crank bearings. Hence the asking for bearing recommendations as well as a case source.
 

rusty.western.flyer

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Maybe difficult to see in this pic, but the jug has a ~1/4" flange to catch socket cap screws that are sent through the jug cooling fins. A stud isn't easily viable, a wrench and nut would have to clear the casting.
 

ImpulseRocket89

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Maybe difficult to see in this pic, but the jug has a ~1/4" flange to catch socket cap screws that are sent through the jug cooling fins. A stud isn't easily viable, a wrench and nut would have to clear the casting.
My stud suggestion wasn't for the jug, it was to fill your drilled/tapped holes to protect them so you could weld in the bolts used to plug the original holes.
 

rusty.western.flyer

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Hard to describe via characters. Pretty sure the tear down pics will explain.

Two of the bolts for the jug actually foul the two top lateral case bolts. Once they are screwed in and machined, no going back. I have a solution for this,but want to prove the long engine before tampering with cases and such.
 

rusty.western.flyer

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I think crazy glue would work. :ROFLMAO: :ROFLMAO: :ROFLMAO:
While you kid, I really do use CA all the time. When making BMW oil drive bearings, I have to turn a blank close enough for super glue to hold a tight fit and easily released. When I'm ready to take the part off the lathe, just hit it lightly with a propane torch as the chuck slows and they pop right off.

I got the idea from a channel on YouTube called "Click Spring".
 

Chainlube

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Hard to describe via characters. Pretty sure the tear down pics will explain.

Two of the bolts for the jug actually foul the two top lateral case bolts. Once they are screwed in and machined, no going back. I have a solution for this,but want to prove the long engine before tampering with cases and such.
Ideally it's a combo of adapter plate, piston and jug. The big question is which jug.
 
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