Noob advice for 028 AV S rebuild

[ashbugwoody]

The rings are intact but have lots of vertical scores on the exhaust side. They might be pinched in the ring grooves also. That same side of the piston has lots of scoring on the aluminum. Pin retainers and pin are all there, they didnt get loose. Piston pin bearings on top are smooth with no up and down slop. Piston crank bearing has no slop in the rod direction, also feels smooth like needles are good. Bottom end bearings also feel smooth without play / slop at the flywheel or sprocket side. Still waiting on the post office to deliver flywheel puller so I have not removed seals yet. Looked real good inside case and see no evidence if metal trash. Sent a small magnet in and it came up clean.

 

[Mad Professor]

I use acid all the time. Just use eye protection, wear gloves, and apply with Qtip and watch. Use common sense. keep a bucket of warm baking soda solution nearby to dip and neutralize the acid on the jug.

Sand a bit and then keep repeating acid. Watch out by port edges, and watch out for areas that keep fizzing with not much apparent transfer-there could be a pit there.

I do acid and sanding together and end with scotchbrite. Sanding alone can polish transfer and not fully remove it in my limited experience. I will sometimes rub some acid over a final repair area and see if it reacts at all. Acid isn’t as perilous as some make it, you just need to pay attention. I wouldn’t soak a rag in acid and leave it in the jug overnight.

I'm on board with the acid method alternating with hand sanding too. Just take off the transfer and don't scratch up the plating.

You do need to be careful handling it and also use in well ventilated area. Hydrogen chloride is actually a gas and it is dissolved in water. Gloves, goggles, and clothing that covers your skin. The baking soda for spills or accidents, and to neutralize things as your working in the cylinder.

You're right the "fizz" tells you if your acid is working on aluminum transfer. The bubbles are hydrogen gas (hydrogen gets reduced and the aluminum oxidized). You have to get any oil or carbon off the transfer for it to work, that's why I use dish detergent solution with wet/dry paper when sanding. The q-tips with the long wooden handles are great applicators for the acid, and a small glass bottle to hold the acid you are working with.

Go slow and just apply to the transfer, rinse with baking soda solution then water, and wet sand again. You have to be careful around port edges to keep off the aluminum. You can smear a little grease there to protect the aluminum

I'd not have the patience to use that method working on somebody else's saws, and that's why shops want to sell you a cylinder.

 

[ashbugwoody]

Acid can be problematic and high risk. If there are any holes in the plating or near a port edge acid will get under the plating and then it is Game Over. Less risky approach is with abrasives. Look for a @Mastermind Worksaws thread that describes the process. If you use a rotary tool and a split mandrel you still need to watch out for the port edges.


Existing piston is toast. Meteor is probably the best AM if it is available for your saw. Use OEM circlips if same size as the meteor or cut the ears off of the meteor. Install either type with the gap facing either up or down.

When you say cut the ears off, you mean before installing clips, right? Should you cut the ears completely off so the clips look like the OEM ones? Thanks.

 

[SteveSr]

When you say cut the ears off, you mean before installing clips, right? Should you cut the ears completely off so the clips look like the OEM ones? Thanks.

Circlips are nothing more than springs. The ears add extra mass at the end of the spring which can cause the clips to jump out of their groove resulting in a trashed cylinder (or worse). This is the same reason to install them with the gap pointing either up or down.

Did you verify if the cylinder gouges were actually through the plating or if it is still transfer? The Nikasil plating is tough stuff and would be difficult to sand through especially by hand. The other thing is to check what is coming off with the sandpaper. If it comes off easy and in volume it is probably still aluminum.

 

[ashbugwoody]

Circlips are nothing more than springs. The ears add extra mass at the end of the spring which can cause the clips to jump out of their groove resulting in a trashed cylinder (or worse). This is the same reason to install them with the gap pointing either up or down.

Did you verify if the cylinder gouges were actually through the plating or if it is still transfer? The Nikasil plating is tough stuff and would be difficult to sand through especially by hand. The other thing is to check what is coming off with the sandpaper. If it comes off easy and in volume it is probably still aluminum.

 

[ashbugwoody]

Seems like that long one in the pic's is a score. I can feel my nail drop in it rather than scrape on something raised. Most of the transfer is out I removed it anyway just to get some practice. If I was to run the Scotchbrite in there with the drill, like in the video, it would be all clean. Thats how little transfer is left. I'm down for a few days, a few of the tools I need are lost in the mail. Cant get to the main bearings yet but I think they are good. Pin bearing looked fine and no slop in the rod bottom bearing. I'm exploring cylinder options now. Thanks for all the help.

 

[drf255]

You can use that jug, it’s not preferred obviously.

As long as the edges of the grooves arent “proud” to the bore (sticking into the bore). The amount of compression you’ll lose from those tiny grooves are 12,000 rpm is negligible. You just don’t want any proud surfaces grooving the rings or piston. Being you used sanding as you method to clean, you likely wore down any high points on the grooves.

Use a meteor piston. I bet you’re fine. Worst case is you ruined a $40 piston, but I doubt it. I just wouldn’t sell the saw without disclosure, but I’d run it as my own saw.

As you already know, you need to figure out why it got toasted in the first place so it doesn’t happen again.

 

[SteveSr]

Seems like that long one in the pic's is a score. I can feel my nail drop in it rather than scrape on something raised. Most of the transfer is out I removed it anyway just to get some practice. If I was to run the Scotchbrite in there with the drill, like in the video, it would be all clean. Thats how little transfer is left. I'm down for a few days, a few of the tools I need are lost in the mail. Cant get to the main bearings yet but I think they are good. Pin bearing looked fine and no slop in the rod bottom bearing. I'm exploring cylinder options now. Thanks for all the help.

A saw that old really should have the crank seals replaced... While they are still available This will at least allow you to see the outside of the bearing retainers and whether they are metal or plastic. I would expect metal for this vintage.

 

[ashbugwoody]

So here is the newest roadblock. I got the Hyway P&C kit (nikasil). As you can see, there is big difference between the OEM c-clip and the one supplied. I have no problem installing OEM clips but a gorilla would struggle with the replacement clip. I cant even get it started good. Before it is 1/2 way around it is already riding out of the groove and impossible to compress. I am waiting to get access to a c-clipper installer but this spring is so stiff, I'm concerned that wont work. Any suggestions.

 

[CausticUC]

If it is the right size to fit the piston's ring groove, it is the right clip.

Those two clips are very different AWG sizes.

 

[ashbugwoody]

Yeah that's what I thought. You can't see it in the pic but the new clip is larger (dia) than the OEM clip sitting on top of it. The dealer that sold me the kit is shipping new clips just to be sure they are right. I can't believe how stiff they are.

 

[CausticUC]

Well, that is the reason for the ear - extra leverage to compress the ring. Pretty sure you are putting it in right as its fairly self explanatory, but just in case:

You put the non-ear end in first and then twist towards the non-ear end to compress, push and snap it in-place.

 

[Mad Professor]

View attachment 869130View attachment 869133
So here is the newest roadblock. I got the Hyway P&C kit (nikasil). As you can see, there is big difference between the OEM c-clip and the one supplied. I have no problem installing OEM clips but a gorilla would struggle with the replacement clip. I cant even get it started good. Before it is 1/2 way around it is already riding out of the groove and impossible to compress. I am waiting to get access to a c-clipper installer but this spring is so stiff, I'm concerned that wont work. Any suggestions.

I'd be worried w/oem clips, the groove in the Chinese piston is too big and would pop out for that reason. Do the chi-com clips fit?

Those clips are FUGLY!!!

 

[ashbugwoody]

In short, I have not been able to get one in. When you lay the clip in to start it, it only rides in the groove for less than 180 degrees. Then you can see it rising up out of the groove. If it is not in there for 180 degrees, you have nothing (except your thumb) to push against to compress it. My thumb loses every time. I don't know WTF, and I have installed clips on many other 2 strokes and never had this kind of problem. Even put the OEM clips back in the toasted piston just for comparison and had no problem.

 

[CausticUC]

Your thumb? Use needle nosed pliers to hold the ear.

 

[ashbugwoody]

I am using my thumb to cover the pin bore and needle nose to grab ear and try to compress it. Clip pops out of groove and bore before I can compress it close to enough.

 

[CausticUC]

I am using my thumb to cover the pin bore and needle nose to grab ear and try to compress it. Clip pops out of groove and bore before I can compress it close to enough.

Maybe try the wiseco non-ear method then:

 

[ashbugwoody]

Notice how the clip doesn't ride the groove even on the non-ear end that is started first. This cant be the right clip.

 

[CausticUC]

View attachment 869163View attachment 869162
Notice how the clip doesn't ride the groove even on the non-ear end that is started first. This cant be the right clip.

Fits about the same way as mine did on the 650i Brute ATV. It's not easy to make them seat and once they are in, not easy to get out!

I suppose its possible it's a bit too heavy. You have to remember the purpose of the circlip is to keep the wrist pin in, it does not sit flush into the groove. Half to 2/3rds rides above the groove to block the pin. All the circlip strength comes from the spring force pushing into the shallow groove.

 

[ashbugwoody]

Partial success, and I'm wrong again. First clip in. Had to jam it in middle first, then flip it so the pin bore held it almost compressed. Then ease it into groove with a dowel. With this type clip I don't think the conventional method of easing it in as you move around the pin bore will ever work. I would much prefer that they stuck with the OEM clip and sized the groove the same.