Baumr Ag/Husky 372 compatibility

[BenC]

I've got a Baumr Ag SX92 that has done remarkably well for a few years, but has now scuffed the piston and scored both it and the cylinder badly. It's a later model (Series 2 it claims) and so is quite different to the earlier ones I've seen discussed. Measurements are 50mm bore and 37(ish)mm stroke, making it 72cc. Piston pin is 10mm. Cylinder bolt spacing is 60mm front-back and 48mm across. Some photos are attached below.

From what I can tell, a round port Husky 372 cylinder could fit it. But I'm not certain. Does anyone have any experience with these and can confirm fitment? Or see any reason why it wouldn't work? A project for educational purposes would be ok, but even better if it results in a running saw.

Thanks

 

[Woodslasher]

I’ve got a loose 372 cylinder, I‘ll go out and measure the bolt spacing later today. Provided that matches I’d say go for it!

 

[Bob Hedgecutter]

Unless you have access to a free 372 cylinder- given your location, if you have to buy a genuine 372 cylinder to try this experiment, you are going to have a very expensive fit for a very cheap saw and if you have not discovered what made the original cylinder look like that- the new one will look the same in short order if it not corrected.
Of course if you are looking at a cheap knockoff copy of a 372 cylinder, then you can afford to just go for it and see.

 

[Czed]

I've got a Baumr Ag SX92 that has done remarkably well for a few years, but has now scuffed the piston and scored both it and the cylinder badly. It's a later model (Series 2 it claims) and so is quite different to the earlier ones I've seen discussed. Measurements are 50mm bore and 37(ish)mm stroke, making it 72cc. Piston pin is 10mm. Cylinder bolt spacing is 60mm front-back and 48mm across. Some photos are attached below.

From what I can tell, a round port Husky 372 cylinder could fit it. But I'm not certain. Does anyone have any experience with these and can confirm fitment? Or see any reason why it wouldn't work? A project for educational purposes would be ok, but even better if it results in a running saw.

Thanks

View attachment 916248

View attachment 916249

View attachment 916250

After talking to some Australian and new Zealand guy's on these forum's.
About the saws from baumr-ag and mtm and johno and johno?
We can't get those brands here but I did import 6 of the complete no name saws
From china.
They appear exactly as the baumr saw do
Just different color.
I've used oem,hyway and farmertec cylinder kits on those saws
Completely interchangeable.

 

[BenC]

Thanks gents.

I can get a rebuild kit, or even 52mm big bore kit, for $75-100 AUD, and I'm willing to invest that into trying/learning, even if it doesn't work out.

Regarding the original problem of scored piston and bore, it looks like either:
- Straight fuel. Unlikely as it definitely had oil at 1:25, though just standard mower 2 stroke oil. Crankcase had oily residue in it.
- Too lean. Quite likely as I'm no tuning expert and may have left the top end too fast and too lean. It started mis-behaving when I was making a series of cuts with minimal pauses.
- Air leak. No idea here, I'll have to check the intake and crank seals after rebuilding.
- Debris in cylinder. The piston crown and head showed clear signs of hitting something hard, and I found a small piece of steel lodged in the crown. NFI where it came from. This may have started the process.

Given my very limited 2 stroke experience I'm a little concerned I'll kill the rebuilt saw in short order, but I'll check the above and ensure it all looks alright before working it hard.

 

[Bob Hedgecutter]

Thanks gents.

I can get a rebuild kit, or even 52mm big bore kit, for $75-100 AUD, and I'm willing to invest that into trying/learning, even if it doesn't work out.

Regarding the original problem of scored piston and bore, it looks like either:
- Straight fuel. Unlikely as it definitely had oil at 1:25, though just standard mower 2 stroke oil. Crankcase had oily residue in it.
- Too lean. Quite likely as I'm no tuning expert and may have left the top end too fast and too lean. It started mis-behaving when I was making a series of cuts with minimal pauses.
- Air leak. No idea here, I'll have to check the intake and crank seals after rebuilding.
- Debris in cylinder. The piston crown and head showed clear signs of hitting something hard, and I found a small piece of steel lodged in the crown. NFI where it came from. This may have started the process.

Given my very limited 2 stroke experience I'm a little concerned I'll kill the rebuilt saw in short order, but I'll check the above and ensure it all looks alright before working it hard.

I would personally hold off ordering a Chinga top end for AU$100 and think seriously about the metal bits on top of the piston, you might have NFI, but I am willing to bet they are bits of one of the bearings on the crank- either case bearings, or perhaps more likely big end bearing.
That kind of means the bottom end is shagged as well and for a Baumr- is it worth the cost in parts?

 

[BenC]

Yes, I've had as good a look around as I can (so far without splitting cases) and no signs of anything disintegrating. Little end bearing is fine. Big end bearing, while hard to see, looks and feels fine. Crank bearings are unknown. I might have to fully strip the thing after all.

I appreciate the advice and suggestions on what to investigate.

 

[Mike Gudgeon]

Have a really good look at that bit of steel you found in there - if you haven't sorted it already. That sort of thing is, as Bob H says, usually indicative of something going badly astray in the gizzards or intake of the saw.

 

[BenC]

So, I eventually got a cheapo 372 big bore kit (82cc) and fitted it to this saw. The cylinder looked a bit rough, so I cleaned up a few things, and chamfered the edges of ports. Timing numbers look reasonable (exhaust 102ATDC, intake 73BTDC), squish was big at 1mm/40 thou even with no base gasket. It runs, seemingly OK on first impressions, but I doubt it has any more power than the previous 72cc version.

I may try porting it slightly, and would love to tighten the squish, but don't have the tools to deck the cylinder. May try a 272 or other piston if I get motivated.

 

[Bob Hedgecutter]

So, I eventually got a cheapo 372 big bore kit (82cc) and fitted it to this saw. The cylinder looked a bit rough, so I cleaned up a few things, and chamfered the edges of ports. Timing numbers look reasonable (exhaust 102ATDC, intake 73BTDC), squish was big at 1mm/40 thou even with no base gasket. It runs, seemingly OK on first impressions, but I doubt it has any more power than the previous 72cc version.

I may try porting it slightly, and would love to tighten the squish, but don't have the tools to deck the cylinder. May try a 272 or other piston if I get motivated.

Smack a bit of mig splatter on the piston and make it a pop up- problem solved.

 

[BenC]

Nor do I have an AC welder. Though, now we're heading that way, how about some buttonhead screws threaded into the top of the piston, or a bit of JB Weld.

 

[Bob Hedgecutter]

Nor do I have an AC welder. Though, now we're heading that way, how about some buttonhead screws threaded into the top of the piston, or a bit of JB Weld.

Perfect- like the hob nailed boots of old.