new to me 036 adventure

[flatsfisher]

it's like Christmas in june (wow, almost july).

 

[flatsfisher]

OEM base gasket.

 

[flatsfisher]

the base gasket used with the AM cylinder appears to be home made and thinner than the stock one.

 

[flatsfisher]

quite a few differences between the OEM and AM top ends. most obvious to the naked eye is the different size piston ports.

 

[flatsfisher]

also the bosses that go around the wrist pin are beefier on the OEM piston.

 

[flatsfisher]

and the reinforcement webbing cast on the underside of the piston crown is much heavier on the OEM.

 

[flatsfisher]

not sure what this huge blob on the AM piston is unless it was to balance the piston.

 

[Mad Professor]

well, just for fun I went ahead and bought this NOS OEM top end from ebay. will be interesting to see if it actually has more power and torque than the after-market top end. it is a KS (Kolben-Schmidt) top end with Stihl markings. includes cylinder, piston, rings, wrist pin and circlips. everything is OEM. I need to find and order an OEM wrist pin bearing today as that was not included. the stock base gasket is 1mm thick. I have an aftermarket base gasket that is .55mm thick. will check squish when the parts arrive in a few days.
View attachment 997699

Good find on the oem top end. $tihl dealers price them like gold.

Stihl gasket set come with seals and both thickness base gaskets.

If you check the squish you might be able to get by with a gasket delete?

 

[Mad Professor]

If you've got a decent scale (+/- < 0.1g) , check mass of both pistons.

And a comparison of the cylinders/ports.

Nice to see side by side OEM vs aftermarket for reference.

 

[flatsfisher]

the cylinder domes are very different. the OEM cylinder has a 33mm dia dome with a 7.49mm wide flat ring around it. I call the flat ring the squish ring. the AM cylinder has a 29mm dia dome with a 9.5mm wide squish ring. moreover, the dome on the OEM is quite a bit deeper than the dome on the AM cylinder.

 

[flatsfisher]

If you've got a decent scale (+/- < 0.1g) , check mass of both pistons.

And a comparison of the cylinders/ports.

Nice to see side by side OEM vs aftermarket for reference.

yeah, I'm getting to the ports here shortly. I'm having to download the photos from my phone to my laptop as I go.

 

[flatsfisher]

I don't have a degree wheel so not sure if these measurements mean much other than to compare the cylinders.

the OEM intake port on the outside at the carb boot has a width of 20.65mm and a height of 18.16mm. the AM is 21.5mm x 19mm.
the OEM intake port inside the cylinder is 25.50mm wide and 15mm high. AM is 25.72mm x 15mm. the intake ports on the inside have very different shapes. from my reading smaller intakes are better for creating velocity. not sure. from squish ring to top of OEM intake port is 39.44mm. AM is 39.26mm.

 

[flatsfisher]

OEM exhaust port on the outside at the muffler is 28.08mm wide x 17.62mm high. AM is 28.45mm x 18.06mm.
OEM exhaust port on the inside of the cylinder is 26.31mm wide x 11,5mm high. AM is 28.45x12.0mm.

from squish ring to top of OEM exhaust port is 23.66mm. AM is 28.45mm.

 

[flatsfisher]

If you've got a decent scale (+/- < 0.1g) , check mass of both pistons.

And a comparison of the cylinders/ports.

Nice to see side by side OEM vs aftermarket for reference.

 

[flatsfisher]

If you've got a decent scale (+/- < 0.1g) , check mass of both pistons.

And a comparison of the cylinders/ports.

Nice to see side by side OEM vs aftermarket for reference.

and just for fun.

 

[flatsfisher]

ok, transfer ports.

lower transfers (the big ones). OEM are 26.51mm wide x 18.60mm high (both are almost exactly the same). AM is 26.54 x 18.77 and also both are almost identical.

squish ring to top of lower transfers on OEM is 45.18 and the other one is 45.24mm. AM is 45.65mm and the other one is 45.20mm.

the biggest difference in the lower transfers, and it's a huge difference is that on the OEM transfers the top is nicely knife edged and on the AM cylinder instead of being knife edged they are hugely rounded. on the OEM ones, the knife edge on the side closest to the exhaust port is 1mm wide and on the intake port side it is 4.5mm.
the AM ones are 4.22mm wide next to the exhaust port and 8.11mm wide next to the intake port.

the OEM squish ring to top of lower transfer ports is 45.18mm on one side and 45.24mm on the other side.
the AM squish ring to top of lower transfer ports is 45.65mm on one side and 45.20mm on the other side.

 

[flatsfisher]

upper transfers (the small ones) are pictured with the lowers above. OEM are 21.23mm wide x 6.54mm high. AM are 21.40mm wide and one is 8.79mm high and the other is 8.36mm high.

OEM squish ring to top of upper transfers is 28.04mm and 27.97mm.
AM is 27.50mm and 27.07mm.

 

[Mad Professor]

Good pictures and thanks for measuring things too. Port shapes, and just the piston windows are going to effect flow.

Here are some pics from an OEM 036 cyl I saved from a straight gas episode (free saw). It was ugly to start with (see piston), but cleaned up nice. I imagine this cylinder is from 1995-1996? I wish I'd saved more pictures

It looks like the chamfers on the ports are a little cleaner than your NOS. I'd not worked on them. I did clean up and match the ex outlet to muffler.

 

[flatsfisher]

Good find on the oem top end. $tihl dealers price them like gold.

Stihl gasket set come with seals and both thickness base gaskets.

If you check the squish you might be able to get by with a gasket delete?

the guy on ebay has 7 more of these kits. also, if I did porting I would def look at the base gasket delete but if you do that without grinding the ports you are moving the port timing from OEM. could be a good thing or a bad thing.

 

[Maintenance supervisor]

I love working on these things. my NOS top end kit will be here tomorrow (UPS usually gets here after dark dammit) so I pulled the top end off in anticipation. took like 10 minutes to get the cylinder off, including cleaning as I went. speaking of cleaning is this a normal amount of crap on the air filter after 4 days or so of cutting (dry, hard oak)? guess I need to clean it more often.
View attachment 998330

The sharper your chain the less dust you have to clean, dry oak can be dirty though.