have I done something REALLY wrong?

[harrygrey382]

ok, I'm reassembling my 056 after a light hone and new rings. I get the jug bolted on fine. Thought I'd do a quick compression test, so screw the gauge in and turn the crank with my thumb. BUT THERE'S NO COMPRESSION! I can spin the flywheel and the gauge doesn't register.

It had 140psi before. I gave it a light hone, didn't do any damage (that I can see). The rings are aftermarket - for an 051. They are exactly the same dimensionally as the old ones, but a very slightly bigger half moon for the pins. They do have a matt black finish though, I gave them a pollish with a plastic scourer but no help.

I put the old rings back in, same deal. So, is this normal? Do you need to spin it fast (with the cord) to get a compression reading. I assume you don't need the carb and impulse line hooked up? It has a new base gasket. What could I have done? I also tried the parkplug in there, same thing.

 

[PB]

You need to pull the pull cord several times to get a reading. Pull it like you are trying to start it.

You can always hold the saw by the pull handle and see if it drops.

Why did you replace the piston ring? 140psi is acceptable.

Lakeside?

 

[harrygrey382]

You need to pull the pull cord several times to get a reading. Pull it like you are trying to start it.

You can always hold the saw by the pull handle and see if it drops.

Why did you replace the piston ring? 140psi is acceptable.

Lakeside?

phew, glad to hear it, i'll get it back together then. Why did I pull it down? Long story, hunting a power loss problem I guess, and suspected the skirt as well as wanting a bit more compression. I also found it is a non-super though, another power thing I guess... Anyway, my first saw apart so experience as well!
Thanks

 

[16:1mix]

Add a little lightweight oil to the cylinder to 'seal' things and expect better compression readings. A dry cylinder will leak compression.

 

[Lakeside53]

:monkey: :monkey: :monkey:


Put a spark pug in and see if you get compression.. I've never had a saw that didn't have a good "snap" to the rotation of the flywheel, especially as I use assembly oil...

 

[blsnelling]

Add a little lightweight oil to the cylinder to 'seal' things and expect better compression readings. A dry cylinder will leak compression.

I would hope he put it back together with a coat of 2-stroke lube.

 

[GASoline71]

Yup... just a light coat of 2 stroke during assembly should be all that is needed.

Gary

 

[Log Splitter]

Yup... just a light coat of 2 stroke during assembly should be all that is needed.

Gary

What kind of 2 stroke do you recommend, Gary?

Sorry, I could not resist, totally bored at work right now.

 

[GASoline71]

The kind you buy at the dealer, or store... comes in these handy little bottles.

LMAO...

Gary

 

[harrygrey382]

well I put it together with a liberal does of mix. I know, should have been pure oil, but didn't have any on hand. I've sprayed some wd40 in there though. I'm only getting a shade over 130psi now. These new rings are much less springy than the old ones, but much more open too. Could the matt finish be affecting the compression - will it improve with running. In fact, do I need to run these rings in now?
Or are they just crap aftermarket, and I should put the old ones back in?

 

[harrygrey382]

uh oh, I just did a search... and found out ring seating is a topic that closely follows oil mix and husky/stihl wars in terms of opinion differences!

I assume I've just got to 'run it in'

 

[Lakeside53]

I'd put real rings in... I see rings out here for as little as 80 cents, but they are junk. At least put in the rings for an 056. The larger ring pin cutouts are likely your problem - a path for leaking compression.

BTW, you can use oil/gas mix for assembly if you like, but gas is not the most pleasant to work with. I use straight mix OIL - any old junk brand.

If you are going to use your old rings, put the ring that has the smallest end gap (size them in the bore) in the top. Some guys put the best ring in the lower slot, and a new ring in the upper. But that's just being cheap

I was up at cheapstihlparts last week and he has a bunch of genuine rings...

 

[blsnelling]

Why did you use 051 rings? OEM 056 rings are available as Lakeside said. It's not worh the hassle to risk it using questionable parts.

 

[sugarbush]

how did you hone it and what with?

 

[blsnelling]

I'm also confused about where you say you polished the matte black finish on the rings with a plastic scourer? Also, you'll never get any reading on a compression guage spinning the flywheel by hand.

I think we need to start afresh here and help you through this process.

1. Start by telling us how you honed the cylinder. An improper hone can ruin a plated cylinder such as you have. Some pics would be helpful in assessing it's current condition.
2. Get yourself a proper set of OEM 056 rings.
3. Assemble with a thin coat of straight oil.
4. Use a new cylinder gasket.
5. Torque cylinder bolts to 132 in/lbs. I think that's 11.5 Nm.

Yes this stuff is simple, but you can't just hack at it and expect it to be right. Don't hesitate to ask questions. We'll help you through it.

 

[harrygrey382]

there are no geniune 52mm 056 rings here, not that the dealers can get anyway. No one has aftermarket 056 52mm rings either, that's why I went 051/064 (not sure which), and they weren't cheap - £13.

I've written to cheapstihlparts about 52mm 056 (he only lists 54mm). So do you reckon there's no point putting it back together with the new rings? I was planning on using it this w/e, what a pain. Maybe I'll put the old rings back while I'm waiting. Will the new ones bed in and get better compression?

 

[blsnelling]

I'm not sure if the new ones are ok or not. You mentioned polishing on them and that the ends are different. It's not worth ruining a good cylinder. You also said you put the originals back in. Is the compression back to what it was? Tell us more about the honing you did.

 

[harrygrey382]

I'm not sure if the new ones are ok or not. You mentioned polishing on them and that the ends are different. It's not worth ruining a good cylinder. You also said you put the originals back in. Is the compression back to what it was? Tell us more about the honing you did.

The rings have a quarter circle cut out each end for the little pins in the piston grooves. The new rings have slightly larger cutouts for a larger pin. I gave them a little scrub to remove some of the matt black finish, there's still some black but they're pretty smoothe now. I didn't try the compression (put the cord on) with the old rings. I could do that though.

To hone, I used a brake cylinder hone, and really didn't take much out. The surface looks very slightly rougher (matt, not shiny), but feels the same. I didn't do it for long, maybe 4-5 seconds total.

I can't see how the new rings would damage the cylinder, but as lake said air may be leaking round the very slightly larger cutouts. They do have a smaller end gap when in the bore than the old ones though. Will they bed in?

 

[blsnelling]

How can you hone a cylinder with ports in it with a brake hone? It would catch on the port holes and tear up either the hone, the cylinder, or both if not careful. You might be ale to do just the compression area above all the ports.

Take a bright light and inspect the cylinder bore closely. Makes sure that you have not worn through the Ni plating anywhere. Make sure there are no "hangnails" on the edges of the port from the hone if it caught. If it looks ok, I'd put it back together with the original rings until I can get a proper set.

How are you resealing the cylinder to the case?

If the end gap isn't proper, they can expand and seize in the cylinder.

 

[harrygrey382]

It would catch on the port holes and tear up either the hone, the cylinder, or both if not careful. You might be ale to do just the compression area above all the ports.

yeah that's what I did, didn't want to risk the stones slipping into the ports, so slid it carefully past them into the compression region and honed, moving up and down slightly, but not so they caught. Looking carefully under a light, I can't see any patch of non-chrome. It's got a brand new stihl gasket for the base