Tightening flywheel nut on Stihl ms170

[Tomyp89]

Next time Mark the nut and the flywheel.
Tighten it to the same mark or a hair further.
Will be close enough.

 

[Dacha]

I would have no problem tightening it by feel, if i locked the piston.

Without piston locked have very little feel.

No convinient place to slot scredriver to lock flywheel unfortunately.

 

[Old2stroke]

I would have no problem tightening it by feel, if i locked the piston.

Without piston locked have very little feel.

No convinient place to slot scredriver to lock flywheel unfortunately.

Many people break fins off by wedging a screwdriver in them

 

[Mad Professor]

I would have no problem tightening it by feel, if i locked the piston.

Without piston locked have very little feel.

No convinient place to slot scredriver to lock flywheel unfortunately.

A length of soft rope inserted into the spark plug hole works great as a piston stop. Just be sure the piston is just above the ex port so you don't jam the rope in a port.

 

[montana59]

A length of soft rope inserted into the spark plug hole works great as a piston stop. Just be sure the piston is just above the ex port so you don't jam the rope in a port.

View attachment 1233221

I use a piece of 3/8 nylon, less chance of getting in port

 

[Dacha]

I was thinking of using nylon or cotton type rope 5-6mm (approx 1/4 inch) double fold, so no end of the rope is going into cylinder, to reduce the chance of fraying residue. Inserting it double folded side rather than loose end side. Also that way it is easier to inspect the rope when taken out if it is intact.

If i ever get around to doing it, or anytime soon.

 

[pioneerguy600]

Anyone remember the bent con rod syndrome on the small saws with the stamped out con rods. I believe Brad Snelling was the first to post about it in a thread on here. A few of the engineer types all piled on that thread and it was determined the best piston stop was the one sold by Stihl made of a white plastic material. Thall added that the plastic stop was designed especially for the 170 sized saws and others with that same style con rod.

 

[Mad Professor]

I use a piece of 3/8 nylon, less chance of getting in port

I was thinking of using nylon or cotton type rope 5-6mm (approx 1/4 inch) double fold, so no end of the rope is going into cylinder, to reduce the chance of fraying residue. Inserting it double folded side rather than loose end side. Also that way it is easier to inspect the rope when taken out if it is intact.

If i ever get around to doing it, or anytime soon.

The rope in the picture is a soft braided nylon, it feeds in the plug hole easy, not sure of dia.?

When you cut nylon rope, fuse the end strands by burning it a bit, and cooling.

 

[Mad Professor]

Anyone remember the bent con rod syndrome on the small saws with the stamped out con rods. I believe Brad Snelling was the first to post about it in a thread on here. A few of the engineer types all piled on that thread and it was determined the best piston stop was the one sold by Stihl made of a white plastic material. Thall added that the plastic stop was designed especially for the 170 sized saws and others with that same style con rod.

I missed Brad's thread and didn't know about the 170 cranks/stamped rods. Will see if I can find it.

Would those 170s get hurt using rope as a piston stop? Soft rope spreads the force out over a good portion of the piston dome.

 

[pioneerguy600]

I missed Brad's thread and didn't know about the 170 cranks/stamped rods. Will see if I can find it.

Would those 170s get hurt using rope as a piston stop? Soft rope spreads the force out over a good portion of the piston dome.

Well I got pretty badly berated for suggesting the rope stop by one of the engineers. He had figured the throw of the crank would be too far out from centerline and that would cause exponentially more force on the rod leading to it bending with the force required to tighten the nut. The proper white nylon stop Sthil recommends allows the piston to be higher up in the bore when the piston acts upon it thus the rod would be more vertical to the centerline and less stress would be exerted upon it from the crank.

 

[Mad Professor]

Well I got pretty badly berated for suggesting the rope stop by one of the engineers. He had figured the throw of the crank would be too far out from centerline and that would cause exponentially more force on the rod leading to it bending with the force required to tighten the nut. The proper white nylon stop Sthil recommends allows the piston to be higher up in the bore when the piston acts upon it thus the rod would be more vertical to the centerline and less stress would be exerted upon it from the crank.

i.e. don't use too much rope.

 

[pioneerguy600]

i.e. don't use too much rope.

The rope compresses too much so to get enough in the cylinder the piston must be down, most times just above the exhaust port. I stopped monkeying around and bought a set of the nylon piston stops, quick and easy to insert and no chance of catching in the exhaust port, when the piston raises up. The white ones are not the best for bigger cc saws, the black ones work better for them. The combustion chamber dome is higher, more pronounced , the ball shaped end of the stop always seems to be pushed into the highest part of the combustion dome.

 

[Dacha]

I have just ordered Stihl piston stop tool - metal one.

There is affordable torque wrench - beam type (not click type). That i may get. That covers required torque value.