HELP! Ground for 038 av

[Sloa]

Hi I am wanting to know if I use both ground wires on a 038av or just one. Had after market handle on worked fine except would not turn off. So prepped original back on but IPL shows both. Is this correct. My thoughts are just the small strap. Sure running with both on would be fine but seems redundant.

 

[MG porting]

One ground wire from coil to switch and one from switch to chassis. Probably the reason why it wasn't shutting down with the new handle.

 

[Coupe]

0ne will be to the coil and the other on to the engine. I would say that is why
it was not working with your new handle. Any bolt that is screwing into your
engine make sure it is nice and clean and put under there.

 

[Sloa]

0ne will be to the coil and the other on to the engine. I would say that is why
it was not working with your new handle. Any bolt that is screwing into your
engine make sure it is nice and clean and put under there

Thanks and yes went back cleaned both screws and piped cleaned holes in handle and case. Replaced rear av rubber and checked wire from coil.
Tried saw with old handle before doing these things above and worked really well, gave it a growl. Must be the resonance through magnesium. But it would still not turn off. So followed up on your thinking. And it will still not turn off.
Please understand I have never worked on a stihl except for the 170 and it only looked similar. Also both handles came looking the same old and new where contact spring was concerned . Up above and seemed to do as expected With locking in choke. Have it positioned properly.
He runs, and turns off and now I know.

 

[Wood Doctor]

I sold my 038 about eight years ago. I should have kept it. Great saw in my book:

New owner still has it and runs it every year.

 

[Coupe]

Thanks and yes went back cleaned both screws and piped cleaned holes in handle and case. Replaced rear av rubber and checked wire from coil.
Tried saw with old handle before doing these things above and worked really well, gave it a growl. Must be the resonance through magnesium. But it would still not turn off. So followed up on your thinking. And it will still not turn off.
Please understand I have never worked on a stihl except for the 170 and it only looked similar. Also both handles came looking the same old and new where contact spring was concerned . Up above and seemed to do as expected With locking in choke. Have it positioned properly.
He runs, and turns off and now I know.

If you have a multimeter check the switch is not faulty because all the switch does is break the
circuit between the coil and the motor. You will also have to make sure you have the wire on the
motor as if not and on the handle everything is rubber mounted so that will not work either.
Find a good spot on your motor under a bolt make sure where it is bedding to and tighten it
up good. I would check switch first because many a good mechanic has been caught out there.

 

[Coupe]

If you have a multimeter check the switch is not faulty because all the switch does is break the
circuit between the coil and the motor. You will also have to make sure you have the wire on the
motor as if not and on the handle everything is rubber mounted so that will not work either.
Find a good spot on your motor under a bolt make sure where it is bedding to and tighten it
up good. I would check switch first because many a good mechanic has been caught out there.

If you test the switch with a multimeter it should show a full circuit one way
on your meter and when you switch it the other way it should show nothing.
Same as pulling one wire off your switch it will run but you will not get it to stop.

 

[Mad Professor]

The top cover screw is a good place to ground it.

 

[Sloa]

The top cover screw is a good place to ground it.

Now spring placed correctly I put both on so it’s carrying more copper bling. Works just the same.one below one above attached to motor mounting screw.

 

[Mad Professor]

Now spring placed correctly I put both on so it’s carrying more copper bling. Works just the same.one below one above attached to motor mounting screw.

That is correct good ground. Screw goes right into crankcase. The wire from the coil goes to the switch, the other wire you just worked on goes from switch to ground.

Have to remember to connect that wire when you put top cover back on.

With switch in off position it grounds the coil (not main ground/that's the mounting bolts, an internal ground). Grounded in off position, open circuit on run/choke. You can test with an ohm meter, on the end of the wire from the coil at the switch, or spade connector at coil.

Both wires from the switch need to be routed through the grommet/hole in the front of the airbox/handle. On the coil, there is wire retainer to route the wire from the coil (not sure all coils have these?). Check wire routing when you put cover on it does not pinch wires, and check/flex AV mounts/bushings look for pinching. I've lost a coil/plug wire when worn mounts pinched it.

Pictures are in the manual, attached.

I have a bunch of 038 , a 038M and 038S----->038M conversions.

 

[Sloa]

That is correct good ground. Screw goes right into crankcase. The wire from the coil goes to the switch, the other wire you just worked on goes from switch to ground.

Have to remember to connect that wire when you put top cover back on.

With switch in off position it grounds the coil (not main ground/that's the mounting bolts, an internal ground). Grounded in off position, open circuit on run/choke. You can test with an ohm meter, on the end of the wire from the coil at the switch, or spade connector at coil.

Both wires from the switch need to be routed through the grommet/hole in the front of the airbox/handle. On the coil, there is wire retainer to route the wire from the coil (not sure all coils have these?). Check wire routing when you put cover on it does not pinch wires, and check/flex AV mounts/bushings look for pinching. I've lost a coil/plug wire when worn mounts pinched it.

Pictures are in the manual, attached.

I have a bunch of 038 , a 038M and 038S----->038M conversions.

Mad professor what in your opinion is the best combination for a conversion .

 

[Mad Professor]

Mad professor what in your opinion is the best combination for a conversion .

I used NOS OEM 038M P/C, and Tecomec 038M when they were still all Italian made.

A good used 038M cylinder and a OEM or Meteor piston would work good too. Note 038 cylinders are sized A and B (stamped on top) , replacement pistons a "hybrid" to fit either A/B. Meteor are sized too. Check clearances and ring gaps.

The old Tecomec P/C were OEM quality.

 

[Mad Professor]

NOS 038S piston (shopworn) vs Tecomec




You have to slot the holes on the cyl to match the 038S case screw holes, a 038S base gasket makes a good template. And grind a bit on the cyl where the screw heads seat, to clearance the screw heads (or screws will try to seat crooked and cross thread). Then open up the holes in the fins to allow the T27 torx driver to get at the screws.

The other thing is the 038M ex port is wider, so need to grind the muffler inlet to match the port outlet.

Below were all NOS assys

Piston Assy Mass (g)	Piston dia. Skirt (in.)	Piston dia. Top (in.)	Cyl bore dia. (in.)	Cyl clearance (in.)	Piston pin. Dia. (in.)	Piston pin Bore (in)	Piston pin Clearance (in.)
O38S
94.48	1.967	1.962 (0.005 taper)	1.969	0.002	0.4725	0.4735	0.001
038M OEM
106.67	2.045	2.039 (0.006 taper)	2.047	0.002	0.4725	0.4735	0.001
038M Tecomec
104.27	2.046	2.041 (0.005 taper)	2.0485	0.0025	0.4725	0.4735	0.001

 

[Sloa]

NOS 038S piston (shopworn) vs Tecomec

View attachment 445727View attachment 445728
View attachment 445729

You have to slot the holes on the cyl to match the 038S case screw holes, a 038S base gasket makes a good template. And grind a bit on the cyl where the screw heads seat, to clearance the screw heads (or screws will try to seat crooked and cross thread). Then open up the holes in the fins to allow the T27 torx driver to get at the screws.

The other thing is the 038M ex port is wider, so need to grind the muffler inlet to match the port outlet.

Below were all NOS assys

Piston Assy Mass (g)	Piston dia. Skirt (in.)	Piston dia. Top (in.)	Cyl bore dia. (in.)	Cyl clearance (in.)	Piston pin. Dia. (in.)	Piston pin Bore (in)	Piston pin Clearance (in.)
O38S
94.48	1.967	1.962 (0.005 taper)	1.969	0.002	0.4725	0.4735	0.001
038M OEM
106.67	2.045	2.039 (0.006 taper)	2.047	0.002	0.4725	0.4735	0.001
038M Tecomec
104.27	2.046	2.041 (0.005 taper)	2.0485	0.0025	0.4725	0.4735	0.001

Pure gold . So let’s say I have an original 52mm p/c with no noticeable rocking with piston but the piston should be changed out do to wear so a good meteor piston with caber rings. The compression must be unreal with the tecomec p/c.
Cylinder already slotted and ready. I took specs of it to set 381 p/c on current. In regards to the case is there an advantage or disadvantage to things like power, low end torque. Feel does one feel just right. With the two handles I’ve tried the aftermarket made saw feel beefy and more substantial where as the Oem 038 handle makes it feel more nimble and with a throatier timber.

 

[Sloa]

I should have drilled those holes in fins as I wallowed out the cylinder head bolt holes getting them off. Now I have to fill. Got my brothers 028 with same issue 3 stuck head bolts, will slot and drill fins for suitable flat head. Want to use 038 as a faller but also want to put it on a shelf. So I’ll make two. Magnesium has a different feel.

 

[Sloa]

This piston is within spec’s so expect cylinder to still be within tolerance.
Pics are not to precise of numbers but did zero in and came up with final being
Skirt….2.046
Top….2.040

 

[Mad Professor]

This piston is within spec’s so expect cylinder to still be within tolerance.
Pics are not to precise of numbers but did zero in and came up with final being
Skirt….2.046
Top….2.040

That is the taper.

You want to measure skirt vs bore. New is ~0.002-0.0025". A caliper has hard time reading 0.001" accurate, but will tell if too tight or loose. When I did measurements I had access to a machine shop/tools. In a pinch you can use feeler gauges. If you see > 0.004" it's not like new.

Pure gold . So let’s say I have an original 52mm p/c with no noticeable rocking with piston but the piston should be changed out do to wear so a good meteor piston with caber rings. The compression must be unreal with the tecomec p/c.
Cylinder already slotted and ready. I took specs of it to set 381 p/c on current. In regards to the case is there an advantage or disadvantage to things like power, low end torque. Feel does one feel just right. With the two handles I’ve tried the aftermarket made saw feel beefy and more substantial where as the Oem 038 handle makes it feel more nimble and with a throatier timber.

The cases are nearly the same besides cyl screw pattern. Have to check clearance issue at clutch side on 038, early case may have to be clearanced/ground . Stihl mentions this if putting a 038 P/C on a 038 case

Crank, flywheel, clutch, ignition (except early points type), the same.

Carbs from 038S usually Tillotson 038M Bing, both have same size venturi, 038 Tillotson carb is smaller. I've ran both 038S Tillotson and Bings and they both run good on same saw. Rebuild kits for Bings are 2-3 X as much.

Mufflers came in 1,2, and 3 port (rare). I've used opened up dual ports.

I should have drilled those holes in fins as I wallowed out the cylinder head bolt holes getting them off. Now I have to fill. Got my brothers 028 with same issue 3 stuck head bolts, will slot and drill fins for suitable flat head. Want to use 038 as a faller but also want to put it on a shelf. So I’ll make two. Magnesium has a different feel.

Not sure what you are asking here? Taking off original cylinder?

 

[Sloa]

That is the taper.

You want to measure skirt vs bore. New is ~0.002-0.0025". A caliper has hard time reading 0.001" accurate, but will tell if too tight or loose. When I did measurements I had access to a machine shop/tools. In a pinch you can use feeler gauges. If you see > 0.004" it's not like new.


The cases are nearly the same besides cyl screw pattern. Have to check clearance issue at clutch side on 038, early case may have to be clearanced/ground . Stihl mentions this if putting a 038 P/C on a 038 case

Crank, flywheel, clutch, ignition (except early points type), the same.

Carbs from 038S usually Tillotson 038M Bing, both have same size venturi, 038 Tillotson carb is smaller. I've ran both 038S Tillotson and Bings and they both run good on same saw. Rebuild kits for Bings are 2-3 X as much.

Mufflers came in 1,2, and 3 port (rare). I've used opened up dual ports.


Not sure what you are asking here? Taking off original cylinder?

Yes sorry I have a terrible habit of mashing my thoughts together. Yes the original cylinder. Poor folks on the McCulloch thread have shown me great patience.

 

[Mad Professor]

Yes sorry I have a terrible habit of mashing my thoughts together. Yes the original cylinder. Poor folks on the McCulloch thread have shown me great patience.

Get a good T-27 like a Whia or Snap-on. And be sure to clean out the T-27 pockets in the screws before trying to remove dirty ones.

 

[MG porting]

Thanks and yes went back cleaned both screws and piped cleaned holes in handle and case. Replaced rear av rubber and checked wire from coil.
Tried saw with old handle before doing these things above and worked really well, gave it a growl. Must be the resonance through magnesium. But it would still not turn off. So followed up on your thinking. And it will still not turn off.
Please understand I have never worked on a stihl except for the 170 and it only looked similar. Also both handles came looking the same old and new where contact spring was concerned . Up above and seemed to do as expected With locking in choke. Have it positioned properly.
He runs, and turns off and now I know.

Most likely bad switch.