A Tail of Two–MS200T–Top Handles & Compression Tests

[arborlicious]

It is not yet the winter of despair but I'm worried for my second born MS200T. I fear that one day it'll no longer be the powerful slayer of hardwood timber as it has been for nigh on five or so years.

 

My first born MS200T (2009 vintage) tests at 135psi cold and 120psi warm (Gunson Hi-Gauge) while the aforementioned second MS200T tested at 150psi cold–and it kicks arse.

 

The older MS200T starts and runs fine but bogs down when in the cut. Based on the above mentioned compression tests I'm thinking time for new rings? 

 

I want to get my old MS200T back in the game before the newer one gets tired. Any ideas.

 

As usual wishing spud was nearby or at least in the same country...

 

[Stubby]

1 hour ago, arborlicious said:

It is not yet the winter of despair but I'm worried for my second born MS200T. I fear that one day it'll no longer be the powerful slayer of hardwood timber as it has been for nigh on five or so years.

 

My first born MS200T (2009 vintage) tests at 135psi cold and 120psi warm (Gunson Hi-Gauge) while the aforementioned second MS200T tested at 150psi cold–and it kicks arse.

 

The older MS200T starts and runs fine but bogs down when in the cut. Based on the above mentioned compression tests I'm thinking time for new rings? 

 

I want to get my old MS200T back in the game before the newer one gets tired. Any ideas.

 

As usual wishing spud was nearby or at least in the same country...

 

Do it yourself if you confident or send it to Spud for a proper birthday .

[arborlicious]

12 hours ago, Stubby said:

Do it yourself if you confident or send it to Spud for a proper birthday .

Assuming the piston and cylinder look fine is it okay to replace only the rings? 

[spudulike]

You can put the rings in the bore and measure the end gap plus measure the ring thickness/depth (where it contacts the bore and the inner surface) in different areas of the ring to check for wear then replace if necessary.

I would try to fit a Meteor piston or a complete top end if the bore is worn - they typically fail near the inlet port! If the rings are significantly worn then fill your boots!

[openspaceman]

9 hours ago, spudulike said:

You can put the rings in the bore and measure the end gap plus measure the ring thickness/depth (where it contacts the bore and the inner surface) in different areas of the *ring* to check for wear then replace if necessary.

I would try to fit a Meteor piston or a complete top end if the bore is worn - they typically fail near the inlet port! If the rings are significantly worn then fill your boots!

If it isn't obvious because Spud  made a typo putting ring where he meant bore:

 

You put a bare new ring in the bore and square it up with a piston, you then use feeler gauges to check the end gap of the ring. Repeat this in several places of the bore. If the gap doesn't vary and the gap is negligible the bore is okay and you may get away with just new rings. I'm not sure of the correct ring gap but it shouldn't be more than 15-20 thou.

 

You can use the old ring as it's the variation in the bore that you are checking to see if it's worth reusing.

[spudulike]

No typo on my side???

[arborlicious]

Okay, got it now. Hopefully have time over the weekend to dismantle the saw and get some measurements.

 

Also, warmed up my other good MS200T yesterday and tested the compression. 150psi cold which dropped to 125psi hot! Is that considered a big drop? I triple checked and still the same. Note: I'm about 1,000m above sea level which makes the reading about 10% lower than beachside saws.

 

Got a mityvac on the way so can see how the crank seals are holding up too.

 

[spudulike]

A new cylinder and piston will give 170 - 180, a reasonably well worn cylinder will give 150 and is a little low but acceptable. Dropping to 125 is a bit low but probably OK for now, it is normal to get a 20psi drop cold to hot.

Ported, it will pull 200 - 220psi due to dropping the base gasket!

[openspaceman]

1 hour ago, spudulike said:

No typo on my side???

Sorry my mistake then, you did mean measure the ring, not something I ever did as a wide ring gap meant a new ring for me. I never found a nikasil bore which was worn other than ones that had obvious damage.

[spudulike]

I was saying to measure the ring in different areas around its circumference to compare the thickness but was trying to say the thickness between the outer surface that contacts the bore and the inner that butts up to the bottom of the piston groove and not the height of the ring as if you laid it flat on a table! Ring wear will give too much end gap and will effect compression.

 

Nikasil can wear due to ingress of fine woodchip, seen a few but not common.