Stihl 038 magnum mods??

[Stihlproincky]

Bought this saw from a neighbor for $75, I'd say it's been almost the best 75 I've spent. About a year ago I tore the intake boot/manifold next to the cylinder, which was when I really started learning about how to work on my own saws, as the dealer didn't fix the problem. Anyways, tonight I decided to tear it down for a checkup, it had been running like it had an air leak, which I found, it was a torn impulse hose. Now this has been a great saw to me, but I'm wondering if there is anything that I can do to boost power/performance while I've got it tore down, I took pictures before I started cleaning it.
Any suggestions on what if anything might benefit or improve this saw? Thanks in advance

Also, I did a compression test, came in at 155-160psi, possibly needs new rings? Shouldn't it be higher than that? And, how's best to clean the exhaust port? Thanks again.

 

[Bob Hedgecutter]

Whilst you have it apart- decarbon the cylinder and piston- will help a bit.
Then consider your fuel oil choices, mixture ratio and tuning to stop the carbon build up again.
Get a new gasket and clean out/off all that RTV silicone all over the place- or delete the gasket if squish allows and use a proper liquid gasket maker in place of the paper gasket.
Clean the exhaust port while the cylider is off by scraping out the heavy stuff and sanding out the fine stuff- if you are that fussy. Flush and clean well before reassembly.
Find a triple port muffler and tune saw to suit.
Good 038M is a good saw- up there with the 044, bit slower and punchier, but up there for an old girl.

 

[singinwoodwackr]

flush out the crankcase with mix gas before you button things up.

 

[ballisticdoughnut]

I’ve got two 038 mags that I’ve churched up a bit. As long as it’s mechanically sound a muffler mod will wake it up a fair bit. Beyond that your looking at porting and timing advance. Here’s a few pics of a muffler on one of mine.

 

[Mad Professor]

155-160 psi is fine for compression. Piston looks OK. While it's apart check P/C clearance. If you don't have mics, feeler gauges work but are cruder. Always use new OEM circlips. Although comp is good a set of rings if you don't need a piston due to wear. Cabers will be <$20 I think

A base gasket delete /set squish, and open up the muffler. Match muffler to ex port. The modification above looks like a good one.

To clean export hit it with brake cleaner first to get oily crap out. Scrape it if caked, Then some wet/dry paper/detergent or wire wheel on a dremel. If you polish the port with fine paper you won't get as much buildup.

If the muffler halves are caked you can put them in a fire and burn the crud out, but not so hot so they glow/melt. Then repaint them.

If the intake boot and impulse line went check the AV mounts. They could have just went because of age too. Pres/vac test won't hurt as the seals are 35+ years old if original. Seals come in a gasket set, and are cheaper than seals alone. May just want to replace seals while it's apart, then pres/vac test when back together

Clean out everything. Under the flywheel and clutch. 35 years a lot of crud can buildup. Check drive gears for the oil pump.

Clean the groove out on the bar, true the rails.

 

[Mad Professor]

I’ve got two 038 mags that I’ve churched up a bit. As long as it’s mechanically sound a muffler mod will wake it up a fair bit. Beyond that your looking at porting and timing advance. Here’s a few pics of a muffler on one of mine.
View attachment 1191584View attachment 1191585View attachment 1191588

Where did you find the deflectors for the ex mod? I'd buy a few of those.

 

[ballisticdoughnut]

Where did you find the deflectors for the ex mod? I'd buy a few of those.

Couldn’t tell you where it came from unfortunately, found it in the scrap bin at work. Been trying to figure it out myself lol.

 

[Stihlproincky]

Did some cleaning last night, it's all ready to go back together as soon as I get some rtv silicone.
Got the cylinder cleaned up pretty good, gonna go do some more cleaning this evening cuz it's raining here, lol

 

[Bob Hedgecutter]

Hardware store RTV silicone has no place on the saw bench.
Use proper liquid gasket maker- not cheap RTV.

 

[ballisticdoughnut]

Hardware store RTV silicone has no place on the saw bench.
Use proper liquid gasket maker- not cheap RTV.

I agree. Better yet just install a OEM cylinder gasket.

 

[Stihlproincky]

Hardware store RTV silicone has no place on the saw bench.
Use proper liquid gasket maker- not cheap RTV.

What stuff/brand should I get? I know stihl recommends derko ht, but I've heard it's not even rated for such. I figured if derko was recommend, similar couldn't be worse.

 

[Stihlproincky]

I agree. Better yet just install a OEM cylinder gasket.

I would, but I was going for a gasket delete, I might just get a new gasket if they're still available.

 

[Stihlproincky]

I misspoke, I picked up some permatex motoseal, not rtv silicone.

 

[ballisticdoughnut]

I would, but I was going for a gasket delete, I might just get a new gasket if they're still available.

They are still available. 1119 029 2302 is the part number.

 

[Bob Hedgecutter]

What stuff/brand should I get? I know stihl recommends derko ht, but I've heard it's not even rated for such. I figured if derko was recommend, similar couldn't be worse.

Dont believe all you have heard or read regarding sealant but RTV is cheap crap and will fail you as a cylinder to crankcase sealer.
Any of the recognised liquid gasket makers will work, some is indeed the same stuff in a different labelled tube.
As you say, Stihl recommends Dirko and indeed use it on many of their small clamshell type engines- yet you have cause to doubt its suitability?
More important is to check you have the available squish space to allow for the deleting the gasket that Stihl saw fit to use, before you go deleting it.
Motoseal will work fine and a much better choice than RTV.

 

[thompsoncustom]

I would, but I was going for a gasket delete, I might just get a new gasket if they're still available.

Dont believe all you have heard or read regarding sealant but RTV is cheap crap and will fail you as a cylinder to crankcase sealer.
Any of the recognised liquid gasket makers will work, some is indeed the same stuff in a different labelled tube.
As you say, Stihl recommends Dirko and indeed use it on many of their small clamshell type engines- yet you have cause to doubt its suitability?
More important is to check you have the available squish space to allow for the deleting the gasket that Stihl saw fit to use, before you go deleting it.
Motoseal will work fine and a much better choice than RTV.

What he said report back with your squish before assembling.

Everyone has a slightly different method for checking squish I find the most accurate way is to take 2 small pieces of solder and place them on the piston in a dab of grease on the PTO and flywheel sides of the piston. Then I bolt the cylinder down and with the spark plug out run the saw over with a small impact on the clutch for a couple seconds. This ensures that the solder is truly squished and there is no spring back. Most people would tell you .020 thousands is safe but you can go down to .015 on that saw without issues if your measurements are correct but I wouldn't recommend under .015 just aim for somewhere in between .015 to .020

I would also recommend Rings like mad professor did above you are already there and it's only gonna help your compression, also hit the cylinder some scotch brite or sand paper to rough it up.

Taking .030 off the keyway is something else you might want to look into

 

[Stihlproincky]

Dont believe all you have heard or read regarding sealant but RTV is cheap crap and will fail you as a cylinder to crankcase sealer.
Any of the recognised liquid gasket makers will work, some is indeed the same stuff in a different labelled tube.
As you say, Stihl recommends Dirko and indeed use it on many of their small clamshell type engines- yet you have cause to doubt its suitability?
More important is to check you have the available squish space to allow for the deleting the gasket that Stihl saw fit to use, before you go deleting it.
Motoseal will work fine and a much better choice than RTV.

Yeah, after y'all said no rtv I looked up some threads, man I feel like a *******, lol. I'll check the squish, thanks guys