What's on your bench today?

[openspaceman]

1 hour ago, littlelionlee88 said:

The time involved to get it bang on may not be feasible but if it was just for shits and giggles i'd try it. Not too sure how an all ready buggered flywheel would take to some butchery though? 

Yes, I'm no machinist but with a flywheel costing £100ish it may be worthwhile. I see some people grind one side of the fixed key to advance the timing but understand the accuracy required.

[bmp01]

16 hours ago, Mark_Skyland said:

This was something I havent seen before.

 

 

 

Saw is a T540XP.

 

Have a guess at what is covering the piston and why.

 

That's a whole lot of ally swarf and big chunks to collect on the piston must happened pretty quick, a few seconds only,  maybe as saw slowed down.

It's piston crown is cracked through. ...? I'm not sure if i can see a cracked piston there or not. Would that be primary or secondary failure? 

Crankcase is brown,  piston is same colour above and below the ring so I'd guess combustion gases below the piston. Edit: but the ring is stuck so that might be a red herring. ..

Don't know what that other 'stuff' is on the piston,  looks like chewed up green plastic,  bearing cage? 

 

Is there any ally below the piston - can't see any, but blurry though. 

 

Good puzzle, another clue please....

Edited November 18, 2017 by bmp01
Comment added

[Macpherson]

3 hours ago, openspaceman said:

Yes, I'm no machinist but with a flywheel costing £100ish it may be worthwhile. I see some people grind one side of the fixed key to advance the timing but understand the accuracy required.

As you asked, here's a link to broaching a keyway in a tapered hole, something I used to do a lot of. 

 

 

 I know this example is much bigger but this is how you would do it but on a smaller scale, the tapered piece of a knackered crank could have a slot milled in it to accept the broach and then be cut to length to forming guide bush, lining it up in the right position would be 'key' .

 Broaching alloy would only require a lightweight bench press which most mechanics will have access to, so a broach of the right width is all you'd need to buy.  Perhaps somebody could make a bit of cash providing this service. 

 

It seems a common problem with other models having the same cheapo design, some huskys as well, I wonder if one tapered sleeve could be used to repair many different flywheels, I would imagine that all the Stihls would have the same taper at least,  cheers.

[Mark_Skyland]

6 hours ago, bmp01 said:

That's a whole lot of ally swarf and big chunks to collect on the piston must happened pretty quick, a few seconds only,  maybe as saw slowed down.

It's piston crown is cracked through. ...? I'm not sure if i can see a cracked piston there or not. Would that be primary or secondary failure? 

Crankcase is brown,  piston is same colour above and below the ring so I'd guess combustion gases below the piston. Edit: but the ring is stuck so that might be a red herring. ..

Don't know what that other 'stuff' is on the piston,  looks like chewed up green plastic,  bearing cage? 

 

Is there any ally below the piston - can't see any, but blurry though. 

 

Good puzzle, another clue please....

Sorry, I meant to post today but have been out enjoying a bit of Christmas festivities.

 

I was going to reveal all but if you after another clue,  this was down to primarily owner and then "mechanic" error, nothing on the saw failed under its own accord.

 

The repair involved a bit of cleaning, a replacement part of sorts, new piston ring and gaskets.  I did it for a good price £80 as the owner is a nice guy and has spent a fair bit on this saw in the past (he is rough with it mind and does like to smash his saws up) and had reached the point that if it needed a new piston and pot it was getting scrapped. That was from my initial analysis of nowt all compression, must be something nasty.

 

 

 

 

[lurkalot]

38 minutes ago, Mark_Skyland said:

Sorry, I meant to post today but have been out enjoying a bit of Christmas festivities.

 

I was going to reveal all but if you after another clue,  this was down to primarily owner and then "mechanic" error, nothing on the saw failed under its own accord.

 

The repair involved a bit of cleaning, a replacement part of sorts, new piston ring and gaskets.  I did it for a good price £80 as the owner is a nice guy and has spent a fair bit on this saw in the past (he is rough with it mind and does like to smash his saws up) and had reached the point that if it needed a new piston and pot it was getting scrapped. That was from my initial analysis of nowt all compression, must be something nasty.

 

 

 

 

Did some ejit try to fill a hole with solder?

[spudulike]

Piston ring in upside down?

[GardenKit]

Looks like maybe someone had had a go at spark plug thread restoration or helicoil fitting and not removed the swarf?

[Mark_Skyland]

2 hours ago, GardenKit said:

Looks like maybe someone had had a go at spark plug thread restoration or helicoil fitting and not removed the swarf?

 

 

Plus they thought it best to pack some grease in there too, I suppose to catch the alu filings, would have then been a good idea to flush it out!  Hence the gunk on top of the piston. That also caused the piston ring to stick in its groove. Luckily no damage to the cylinder so new piston ring and a couple of gaskets, plus the new helicoil it runs like a good un.

 

 

[spudulike]

Mmm, nice bit of helicoil left sticking out of that hole. Guess the "other guy" was far cheaper, promised the world and produced......the stuff the soil pipe takes away!

You pays your money and ...............!!!

[openspaceman]

8 minutes ago, Mark_Skyland said:

Plus they thought it best to pack some grease in there too, I suppose to catch the alu filings, would have then been a good idea to flush it out!  Hence the gunk on top of the piston. That also caused the piston ring to stick in its groove. Luckily no damage to the cylinder so new piston ring and a couple of gaskets, plus the new helicoil it runs like a good un.

I cannot see much excuse for this with a saw engine but have done it on a subaru boxer engine, to save taking the engine out.

 

The idea is you fill the cylinder with grease as it come up toward, but not at, TDC, tap and insert the helicoil, then eject the swarf with the grease by bringing piston up. Spin the engine over a few times on starter and then put plug in.