Stihl 024 air leak

[ihatesaws]

47 minutes ago, spudulike said:

The oil tank state won't change anything and a tank full of nuts and white spirit will loosen up any loose paint rather than stripping it down. 

 

 

I'm not worried about the oil tank but the same paint loss is around and underneath the crank so bits of paint will be coming up inside the cylinder.  I can fill it with white spirits alright but I don't think I should be throwing nuts down there.  What are they supposed to do, bang against the paint and knock off loose stuff?

[spudulike]

It is an old way of cleaning loose stuff from small tanks. Think of rush on a motorbike fuel tank, that sort of thing....it removes the loose stuff.

[ihatesaws]

I installed the meteor piston into the oem cylinder.  I got a compression reading of 140psi.  I ran the saw for around ten minutes, cutting small bits and pieces and leaving it idle.  It was definitely more powerful than before and the idle with the wte1 carb seemed acceptable.  Before testing any further I took off the exhaust to look at the piston and there seems to be vertical lines worn through the machining marks.  I took off the cylinder and it seems to have more damage than when I put it back on.  There is a vertical line to the right of the exhaust port and a small round chip to the left that i can feel with my finger nail.  I've sanded the area again and this is how it looks now.  The compression was still 140psi after running it btw before taking it apart. There is some stuff on the roof of the cylinder and in the ports that I can't reach to clean out.  Any tips? 

[Muddy42]

Sorry your photo isn't the best - but either the cylinder could be past repair or just requires more polishing.  Generally people say your fingernail shouldn't catch on anything.

 

Meteor pistons tend to be good, are you sure it is the right size, how did the fit feel, any rocking?

[ihatesaws]

2 hours ago, Muddy42 said:

Sorry your photo isn't the best - but either the cylinder could be past repair or just requires more polishing.  Generally people say your fingernail shouldn't catch on anything.

 

Meteor pistons tend to be good, are you sure it is the right size, how did the fit feel, any rocking?

 

I've attached another one.  I've gone through the plating in the spot on the left but I'll keep sanding on the right.  The piston seemed tight enough but what do I know?

 

The piston felt tight.

[spudulike]

The black bit just under the left hand side of the port on your second picture looks like it has had chemical on it but the oxide is still present. This mark coincides with the most wear on the piston.

The vertical score will lower compression, the high points will wear the piston and ring lowering compression.

On this sort of repair, there should be no high bits or deep scores. The scores you may get away with if they are not too deep.

All you can do is see how it goes from what you have. The engine will bed down and get better with use sothe best option is to stick some hours on it. If you persist in rubbing small areas of the cylinder, you are likely to cause very small cavities and that really will kill your compression and cause blow by on the ring!

140psi is a bit low on a 024 but it may just be your compression gauge. 

[Muddy42]

13 hours ago, spudulike said:

The black bit just under the left hand side of the port on your second picture looks like it has had chemical on it but the oxide is still present. This mark coincides with the most wear on the piston.

The vertical score will lower compression, the high points will wear the piston and ring lowering compression.

On this sort of repair, there should be no high bits or deep scores. The scores you may get away with if they are not too deep.

All you can do is see how it goes from what you have. The engine will bed down and get better with use sothe best option is to stick some hours on it. If you persist in rubbing small areas of the cylinder, you are likely to cause very small cavities and that really will kill your compression and cause blow by on the ring!

140psi is a bit low on a 024 but it may just be your compression gauge. 

 

Agree.  I've concluded that I have over-rubbed a cylinder recently which resulted in too poor compression to run.  But then if you leave marks you wear the piston.  This is why some cylinders are beyond it.  All you can do now is run it - use plenty of 2 stroke oil when assembling the piston and in your mix. 

Edited July 4, 2023 by Muddy42

[openspaceman]

10 minutes ago, Muddy42 said:

Agree.  I've concluded that I have over-rubbed a cylinder recently which resulted in too poor compression to run. 

Nikasil is a deposit on the aluminium that is only about 20 thou thick so rubbing or honing is only really to scratch circumferential micro grooves to hold oil.

 

The big thing is to remove all the aluminium which has been picked up from the piston and melted onto the bore with chemicals and only lightly hone after.

 

IME the nikasil hardly wears at all on a saw but, from what @adw has posted in the past, stone cutters with poor filtering make short work of it with concrete dust.

 

I am still using 30 year old saws for the little firewood I need and at most they need a new ring as long as they haven't seized.

[Muddy42]

1 hour ago, openspaceman said:

Nikasil is a deposit on the aluminium that is only about 20 thou thick so rubbing or honing is only really to scratch circumferential micro grooves to hold oil.

 

The big thing is to remove all the aluminium which has been picked up from the piston and melted onto the bore with chemicals and only lightly hone after.

 

IME the nikasil hardly wears at all on a saw but, from what @adw has posted in the past, stone cutters with poor filtering make short work of it with concrete dust.

 

I am still using 30 year old saws for the little firewood I need and at most they need a new ring as long as they haven't seized.

 

Yes I agree with that.  My cylinder looked very like the pictures above with deep scoring and gouges.  Maybe too much sawdust got past the air filter (husqvarna ranchers are known for a flawed choke and air filter design), or it was poorly tuned or used with poor fuel?  Anything could have happened over its 30 years. I'm going to have to try an aftermarket cylinder and piston next.

[spudulike]

I have seen poor filtration cause the Nikasil to wear on the inlet side. It is damn tough but given enough fine wood chip dust through a dirty air filter and it will wear through in time.

Funnily enough, the saw in mind was a 024 with a wire mesh air filter.