Very Early 038AV Chain Brake and Ignition Parts Questions

[TheTone]

Just started work on an 038AV with a seven digit (!) serial number. The P&C are pristine and the bottom end seems solid. It's missing some chain brake parts (photos 1 and 2) which would be hard to find. My question is: was the PTO side of the case changed when the later chain brake parts were instituted? If not, I figure I can retrofit the newer parts. Also, the electronic ignition is different and it has no spark. Is there a newer coil which could be installed after removing the under-the flywheel component that would work with the old flywheel (#3,4,5)? The compression is 158 psi and, if not for these problems, all I would do is carb rebuild (Tillotson), new Cabers and seals, assuming the rubber lines are serviceable.

 

[Mad Professor]

What's under the flywheel is the generator for optional handlebar heating system. You should have some extra wiring and heating elements in handlebars if it's all still there. That stuff is rare save it even if you don't use it.



Not sure on chain brake as never had a real early one? I assume yours is 48mm bore and metal fuel tank? That is the real early original clutch, I think some of the oil pump drive parts might be different too. Here is some more scans from the 038 shop manual. I didn't read through it all, but has some good info






Maybe Jerry @pioneerguy600 knows about the chain brake ? He's an old time stihl/chainsaw lover.

 

[pioneerguy600]

I don`t have much info on the early 038 chainbrake as to what is different from later models but I think the saw in the OP`s pic is an early points/condenser saw. I don`t see the magnets on the flywheel for a generator. I could be wrong though as my eyes are not as sharp as they used to be and my screen today is quite small.

 

[TheTone]

What's under the flywheel is the generator for optional handlebar heating system. You should have some extra wiring and heating elements in handlebars if it's all still there. That stuff is rare save it even if you don't use it.

I don't think it's a generator. There is no wire leading to an output to handle or carb (see photos), also no carb heat plate or wires to the handle. The generators have visible rectangles on the edge with stacked metal sheets like a magneto. I've run across one of these circular units like the one on this saw before, but since it had spark I left well enough alone. I think it is part of the early electronic spark generation/timing mechanism. The resistance across this unit seems high at 125K ohms, but I have no reference to go on.

I don`t have much info on the early 038 chainbrake as to what is different from later models but I think the saw in the OP`s pic is an early points/condenser saw. I don`t see the magnets on the flywheel for a generator. I could be wrong though as my eyes are not as sharp as they used to be and my screen today is quite small.

There was no points plate, but i wonder if this circular unit was mounted to the case in the same holes as the plate was in earlier models. The only magnets I saw were the usual two on the outer edge of the flywheel, and they tested strong.

There seemed to be a bad connection where the plug wire joins the coil module. I snipped off a bit of wire and screwed it back in and got 9000 ohms from boot to coil ground, which seems reasonable. Will try temporary reassembly and see if it will give a spark.

 

[TheTone]

The ignition problem is a moot point now. With everything cleaned up and tweaked as in previous post, I get a good blue spark. All that's left now is the chain brake question: was the PTO side of the case modified to accept the newer chain brake mechanism? My guess is no. Probably the new chain brake, clutch sprocket and oil pump drive mechanisms were modified to fit the original case. This seems like the most cost effective solution. But then again this is Stihl German engineering . . .

 

[Mad Professor]

I don`t have much info on the early 038 chainbrake as to what is different from later models but I think the saw in the OP`s pic is an early points/condenser saw. I don`t see the magnets on the flywheel for a generator. I could be wrong though as my eyes are not as sharp as they used to be and my screen today is quite small.

Well, I've been wrong before and will be again.........