I need another piston and cylinder.. again!

[BrettS]

I had that with a MS260 I rebuilt (circlip came out), made a mess.
I rebuilt it with a new AM piston/cyl and it's still going strong years later.
What I do is cut the ears off of the circlips and face the opening on the circlip straight down.

 

[ericm979]

Quadruple check that the circlips are fully seated. Push in with a tool. I install one circlip on the bench before putting the piston on the rod. Always use the same brand circlip as piston. The grooves are not always the same dimension between piston brands. Never reuse a circlip. Don't "screw" the circlips in, that can twist them.

 

[501Maico]

MagraAdam when you rebuild it this time make sure the opening for the circlips are facing straight up or straight down. Do not leave them facing side ways.

I was a motorcycle mechanic years back and learned 2 circlip rules. If you remove them always replace with new, and the above text on positioning. Circlips tangs are very light weight but think about how quickly and often a piston changes direction.

 

[Jed1124]

Were the clips OEM? Always use OEM clips even when using an aftermarket piston and cylinder.

 

[3000 FPS]

I was a motorcycle mechanic years back and learned 2 circlip rules. If you remove them always replace with new, and the above text on positioning. Circlips tangs are very light weight but think about how quickly and often a piston changes direction.

Yes as high as 13,000 rpm's or more.

 

[wardog]

I'm a chainsaw mechanic novice as I have to take them to have them worked on but wanting to tinker with one that my cousin's Stihl 029 blew the plug out of the cylinder and ruined the threads. We tried to retap them with the kit to do so but was too far stripped out. When we tried to remove the motor from the case the last of the four bolts on the bottom busted the socket inside the head of the bolt. Now will have to destroy the case to remove. I see in this thread many speaking of aftermarket cylinder kits and that is what I was planning to use to try to rebuild this one. Bear in mind that this is not a saw that is a must use but rather would be a backup for when we cut firewood. I know most experienced saw men would probably not use aftermarket parts but just curious of how much worse the quality is from those that have used them.

 

[eriklane]

Running lean on the top end can blow a p&c also.

 

[BrettS]

I'm a chainsaw mechanic novice as I have to take them to have them worked on but wanting to tinker with one that my cousin's Stihl 029 blew the plug out of the cylinder and ruined the threads. We tried to retap them with the kit to do so but was too far stripped out. When we tried to remove the motor from the case the last of the four bolts on the bottom busted the socket inside the head of the bolt. Now will have to destroy the case to remove. I see in this thread many speaking of aftermarket cylinder kits and that is what I was planning to use to try to rebuild this one. Bear in mind that this is not a saw that is a must use but rather would be a backup for when we cut firewood. I know most experienced saw men would probably not use aftermarket parts but just curious of how much worse the quality is from those that have used them.

I've not had much trouble with AM parts but in saying that, have had a cyl/piston ruined by the piston pin circlip coming out and a piston pin alignment issue on a AM piston for a Stihl FS85 I rebuilt, generally though no problems. I have read that piston port timing 'may' be a little off compared to OEM.

 

[BrettS]

Were the clips OEM? Always use OEM clips even when using an aftermarket piston and cylinder.

I don't know, I have had a good run with AM circlips once I cut the little tang off of the circlip, I have also found I couldn't use the OEM circlip in the AM piston as the groove was too big in the AM piston and the OEM circlip just rattled around and wasn't a snug fit.

 

[ericm979]

I don't know, I have had a good run with AM circlips once I cut the little tang off of the circlip, I have also found I couldn't use the OEM circlip in the AM piston as the groove was too big in the AM piston and the OEM circlip just rattled around and wasn't a snug fit.

That's why I use the circlip from the piston manufacturer. Or at least measure the two clips to make sure the new one is the correct diameter wire.

Besides putting the gap at the bottom (BDC has fewer Gs on the piston than TDC) I use a stone to round off any sharp points on the circlip wire.

 

[MagraAdam]

Silly question. But how do you get it in and out if the ear is cut off the clip?

 

[trains]

Silly question. But how do you get it in and out if the ear is cut off the clip?

There is usually a recess next to the seated area of the circlip so you can use a fine scribe, or pointer to carefully lift it out, if its correctly fitted, as others have already mentioned, the gap should face upwards, ie 12 o clock, or 6, and if its fitted like that, you will have some of the circlip going past the area where you can lift it out with a fine point punch etc so you dont scratch the piston.
Really sorry to see it fail, and right now when you need to use it the most.

 

[Shaun Bowler]

I am sorry that I do not have the time to read the entire article. Nevertheless, I guess I can understand the interest in having "fun" rebuilding two stroke engines.
Otherwise, why would you waste your time doing it.
F China. Biden/Harris 2024!

 

[Smitty Smithsonite]

A habit from cutting my teeth on motorcycle engines is putting the circlip opening opposite the relief in the piston for future removal, and angled downward slightly. About the 4:30 position. I take a socket that just fits the pin bore and rap on it a few times with a hammer to be sure that clip is seated, then I'll look at it very close to make sure it is. Knock on wood, haven't lost one yet, and I've reused many on handheld equipment. Never on motorcycles, though, due to the expense and potential safety hazard.

 

[bwalker]

Buy cheap Chicom junk and this is what happens.

 

[thenne1713]

So. Some of you might have seen my previous thread about fixing up an fs450. We'll all was fine and I was using it today for some light work when suddenly it made a sound like something letting go, and no more revs. Walk back to the garage and pull the cord (gently) and no movement. Remove the exhaust and the piston actually looked fine. I forced the flywheel to turn and the piston would go down but not up past where it was stuck. I removed the cylinder and yep, it's pretty bad. Photos below..

My question is, is this caused by running lean (I had the fixed jet carby on it that it came with but had moved up to the fs480 piston and cylinder. I was running 32:1 and had a new filter and plug)
Or was it caused by using Chinese parts?

View attachment 947290View attachment 947291View attachment 947292View attachment 947293

Yep, looks like a clip fell apart.. Once piston/clip tried to lock/seize the piston, it destroyed the Main Bearing CAGE and needles came out? It happens, I have read..


View attachment 947439View attachment 947440

 

[BrettS]

Buy cheap Chicom junk and this is what happens.

Not all the time...

 

[serdie]

Not all the time...

I use hardened expansion clips a reverse snap ring if you will. You’re all correct on tang position

 

[scor440tk]

Do you mean the bearing in the con rod where the piston connects?

Ummm you didn’t know what frank meant i think you better get some help this time?