FS360 seized

[openspaceman]

Last week was unlucky but this week looks better...

 

The story; I was asked to demonstrate strimming so dug out my 1993ish FS360 which I only use in the garden nowadays, it hasn't done much work as we were mostly harvesting those days.

 

Ran through the start routine, told the lad to stand back 3m and started her up no problem. Cut a few brambles to clear the engine out of accumulated 2t in the crankcase but it wouldn't come up to speed, four stroking like the choke was half on. Thinking the air filter was clagged I took out the inner element and started it again, ran like a goodun but after a few seconds it started playing up and stopped. No amount of fiddling would get it going so I felt sure it had seized. I left it in the workshop saying I'd look at it later but curiosity overcame the fitter and he had a peer down the carb and saw scoring on the piston.

 

 

 

See pictures of strip-down below.

 

 

This shows damage to the ring lands

 

 

This shows damage on the other side and the air inlet area of the piston.

 

 

More detail of damage at inlet side

 

 

This shows corresponding damage to the cylinder

 

 

And this shows the culprit, a steel pin 8mm long and 0.75mm diameter

 

It must have been floating around inside the air filter for a while but where could it have come from?

 

I don't know whether the cylinder is recoverable and whether I would get away with just piston and rings?

 

I'm also loathe to do anything without establishing what may have happened to cause the pin to get into the motor.

 

Or shall I relegate it with the Makita backpack blower with possible faulty coil and old Tondu hedge cutter to the scrap and get some new Stihl gear...

 

Seems a shame to waste all those microdots Stihl and Datatag put on for me!

[GardenKit]

Last week was unlucky but this week looks better...

 

The story; I was asked to demonstrate strimming so dug out my 1993ish FS360 which I only use in the garden nowadays, it hasn't done much work as we were mostly harvesting those days.

 

Ran through the start routine, told the lad to stand back 3m and started her up no problem. Cut a few brambles to clear the engine out of accumulated 2t in the crankcase but it wouldn't come up to speed, four stroking like the choke was half on. Thinking the air filter was clagged I took out the inner element and started it again, ran like a goodun but after a few seconds it started playing up and stopped. No amount of fiddling would get it going so I felt sure it had seized. I left it in the workshop saying I'd look at it later but curiosity overcame the fitter and he had a peer down the carb and saw scoring on the piston.

 

 

 

See pictures of strip-down below.

 

[ATTACH]168330[/ATTACH]

 

This shows damage to the ring lands

 

[ATTACH]168331[/ATTACH]

 

This shows damage on the other side and the air inlet area of the piston.

 

[ATTACH]168332[/ATTACH]

 

More detail of damage at inlet side

 

[ATTACH]168333[/ATTACH]

 

This shows corresponding damage to the cylinder

 

[ATTACH]168334[/ATTACH]

 

And this shows the culprit, a steel pin 8mm long and 0.75mm diameter

 

It must have been floating around inside the air filter for a while but where could it have come from?

 

I don't know whether the cylinder is recoverable and whether I would get away with just piston and rings?

 

I'm also loathe to do anything without establishing what may have happened to cause the pin to get into the motor.

 

Or shall I relegate it with the Makita backpack blower with possible faulty coil and old Tondu hedge cutter to the scrap and get some new Stihl gear...

 

Seems a shame to waste all those microdots Stihl and Datatag put on for me!

That pin looks like a roller from a con rod bearing.

[spudulike]

That pin looks like a roller from a con rod bearing.

 

Lost likely cause, also looks like a small end roller but dont think it could pop out!

[openspaceman]

Lost likely cause, also looks like a small end roller but dont think it could pop out!

 

The coincidence of the air filter being out and the fact that the big and small ends seem fine plus the fact the damage is from the inlet port makes me believe it was a tramp bit of metal in the carb housing but I cannot think what. I have had it from new and only cleaned the air filter, not done anything else on the engine.

 

Anyway what thoughts about the prognosis?

[bobh]

Its not the pivot pin from the metering arm is it?

[openspaceman]

Its not the pivot pin from the metering arm is it?

 

I've just checked with some Walbro spares and that is 13mm by 1.5 mm whereas the piece that did the damage is 8mm by 0.75mm

[peatff]

It looks like a pin that holds a wrist watch strap on, have you broken a strap while cleaning the filter ?

[openspaceman]

It looks like a pin that holds a wrist watch strap on, have you broken a strap while cleaning the filter ?

 

No, I haven't warn a wrist watch for over 30 years.

[openspaceman]

 

Anyway what thoughts about the prognosis?

 

A bit lacking for ideas I see.

 

I spoke with the local Stihl dealer and they wanted 250 quid for a new pot and piston. I aked them if they would hone the bore and just supply piston and rings but nowadays they will not even lightly hone bores.

 

I haven’t seen any after-market offerings for this engine but would any of the other 44mm Stihl pistons be the same?

[openspaceman]

A bit lacking for ideas I see.

 

I spoke with the local Stihl dealer and they wanted 250 quid for a new pot and piston. I aked them if they would hone the bore and just supply piston and rings but nowadays they will not even lightly hone bores.

 

I haven’t seen any after-market offerings for this engine but would any of the other 44mm Stihl pistons be the same?

 

Can anyone help with some part numbers?

 

I have found a Meteor kit for a 460 but the bore is 46mm, I have measured my FS360 at 44mm. Are the pot and piston off the later model interchangeable?