029 w 125psi-rings, piston kit, or BB?

[kcr357]

Saved this decent 029 super off of some offerup dimwit who bought and sold small engine stuff. Didn't even have 2 stroke oil in the gas when I brought it home.

Saw runs/ran great. I was in the process of removing the cylinder to decrease squish to .020ish(someone already removed the gasket...) Checked compression before I started and it's damn low. 125. Piston and rings are in great shape, as is the cylinder. Visually at least.

Im quite knowledgeable on dirt bikes and jet skis, saws not so much. Would a ring set be ok, or is a piston kit in order?

OR, I've noticed there are quite a few really reasonably priced BB kits on ebay, which would be awesome, but Im guessing you get what you pay for with these.

Edit-anyone have experience with these?
https://www.ebay.com/itm/THE-DUKES-...700116?hash=item42050ed6d4:g:pNMAAOSwrL9dtfnT

 

[Captain Brown]

125 psi where I live is excellent compression, but I live at almost 8,000 ft above sea level, so everything is lower when it comes to compression. I have a few saws with barely 100 psi. Last summer, I purchased that same kit for a friend's 290 that he wanted rebuilt, and it ran pretty good after I put it back together, and he is always telling me how much more power it has now. He has cut several cords of wood with it, and no problems. Also, removing the gasket on those for higher compression is a no go, with the engine being a clamshell. If you want more compression, I think there is a pop up piston on the market for the 390 cylinders, you could always go that route if you do put the big bore on.

 

[Captain Brown]

Edit to my previous post, I think those saws came out of the factory with no gasket, just a sealant to seal the engine together.

 

[67L36Driver]

SOP in my garage is to drop in a complete Farmertec MS390 engine and send them on their way.

Save the leftover parts from the 290 for patch jobs.

You may have to wait a spell as shipping from China is in flux.

 

[kcr357]

Thanks to both of you. Going with a 390 kit.

 

[kcr357]

of course now I have to buy the domed piston. These things are worse than jet skis, can't quit spending money on them.

 

[67L36Driver]

Thanks to both of you. Going with a 390 kit.

Tip: Use the machine thread screws that come with it.[emoji108]

The fast lead self tapping screws Stihl used suck big time. [emoji90]

 

[SteveSr]

[QUOTE="kcr357, post: 7275005, member: 124012" Checked compression before I started and it's damn low. 125. Piston and rings are in great shape, as is the cylinder. Visually at least.[/QUOTE]

Your compression gauge may be suspect if it is not designed for small displacement engines and doesn't have a low pressure Schrader valve in the tip of the hose. You may not need a top end at all! If you do tear it apart I would measure the ring end gap as the "wear indicator".

 

[kcr357]

Tip: Use the machine thread screws that come with it.[emoji108]

The fast lead self tapping screws Stihl used suck big time. [emoji90]

Any recommendation on a cylinder? Definitely getting a domed piston, need to find a good cylinder. Is a used oem stihl a better idea than am?

 

[kcr357]

[QUOTE="kcr357, post: 7275005, member: 124012" Checked compression before I started and it's damn low. 125. Piston and rings are in great shape, as is the cylinder. Visually at least.

Your compression gauge may be suspect if it is not designed for small displacement engines and doesn't have a low pressure Schrader valve in the tip of the hose. You may not need a top end at all! If you do tear it apart I would measure the ring end gap as the "wear indicator".
[/QUOTE]
Had it for years, it's accurate. Saw is already stripped down

 

[drf255]

BTW, that’s a clamshell. You can’t adjust squish in any way simple. You’d need to weld a piston crown and turn it down on a lathe to spec, or machine the bearing pockets and mill the crankcase lower half to make up the difference. You’re pretty much stuck with what you’ve got.

IIRC, the 029 Super is more displacement than the regular 029. Don’t toss your OEM setup, it may make more power than the 390 China crapola.

 

[kcr357]

BTW, that’s a clamshell. You can’t adjust squish in any way simple. You’d need to weld a piston crown and turn it down on a lathe to spec, or machine the bearing pockets and mill the crankcase lower half to make up the difference. You’re pretty much stuck with what you’ve got.

IIRC, the 029 Super is more displacement than the regular 029. Don’t toss your OEM setup, it may make more power than the 390 China crapola.

Never thought of that. Yeah, no adjusting squish whatsoever. What about an oem 390?

 

[kcr357]

BTW, that’s a clamshell. You can’t adjust squish in any way simple. You’d need to weld a piston crown and turn it down on a lathe to spec, or machine the bearing pockets and mill the crankcase lower half to make up the difference. You’re pretty much stuck with what you’ve got.

IIRC, the 029 Super is more displacement than the regular 029. Don’t toss your OEM setup, it may make more power than the 390 China crapola.

Also, that chinese cylinder I posting in the first post, upon looking at the pics close up, appears to have been worked on in someone's garage using a dremel tool. Chamfering looks awful, the crosshatching looks worse, and these's metal flaking off the transfer ports.