Stihl MS440 piston with new rings wont go into cylinder

[brandonstc6]

I have an MS440 that had bad rings. I pulled the cylinder and removed the old rings and cleaned the carbon from the ring grooves. I then installed new caber rings. Using a ring compressor, I cannot get the piston and rings to go into the cylinder. I have replaced rings several times before and have not had any problems. The piston does into the cylinder fine without rings. The ring gap is .008" with the ring about 1/2" below the bottom edge of the cylinder (gasket surface). What could be wrong? thanks

 

[alexcagle]

I've had that happen before too. Your ring grooves may need a little more of the bottom scraped out with an old ring. Make sure you get the area around the locator pin good too.
Try one ring at a time to isolate which one has the issue.
If no luck, try filing just a wee bit off the ring end to end up with .010 or .012

 

[blsnelling]

Don't file the rings. Find the problem and fix it. Otherwise, I'd do as already suggested.

 

[alexcagle]

Just because a set of rings gaps ok in the bore doesn't neccessarily mean they aren't a couple hundred thousands too thick in depth.
I have seen it before in a Caber ring. You might want to measure them.
Check your cylinder bore for slight out of roundness. A worn piston and rings may have tolerated an out of round cylinder that ; who knows; -may have been dropped or had a tree fall on it in the past.
Being piston ported, I would just put a piston kit in It, If you are going to all that effort anyway.
If the rings are worn, chances are the skirt is too. You could have spitback through the carb as the saw warms up to operating temp.

 

[idiotwithasaw]

Your ring on upside down?

 

[alexcagle]

Just turn the saw over. That will fix it. Lol

 

[kevin j]

end of ring on top of locating pin partially?

 

[brandonstc6]

I tried everything mentioned above and i finally got the piston and rings into the cylinder. I never could get my set of ex-bore ring compressors to work. I had to install the top ring with a zip tie then remove the zip tie then install the second ring from the bottom and compress it with tiny screwdrivers and the cylinder went on. The set of ring compressors i bought came from ebay and included a piston holder and two piston stops. Has anyone had any luck with this type of ring compressor? The piston doesn't look to have too much wear on the skirt and the cylinder wasn't out of round. I have installed new bearings and crank seals too. Ive had to use parts from several saws to hopefully get a good one.

 

[old guy]

I have a ring compressor set like that and I really like it.

 

[kevin j]

What was the original cause why not fit?

Compressing the rings is routine but it sounded like you had more interference than that.

I have many types of compressors and the split plastic ones i like for saws and motorcycles.

 

[brandonstc6]

I'm not really sure. I scraped the ring groove again and only a minuscule amount of carbon came out. I guess the rings were just thick and hard to compress. I think they may have been the new caber f-cast rings. I used the red split plastic ring compressors.

 

[ANewSawyer]

I have a kit I bought with four different sizes of ring compressors, a piston rest and a couple of useless piston stops. Red, says made in Italy, IIRC. Worked great on my T-25.

 

[backhoelover]

i have the same kit. i use to use it alot till i got the kit from @Definitive Dave that stihl sales
http://www.ebay.com/itm/Stihl-Chain...006767?hash=item4aed8cc9af:g:iF0AAOSwDNdVruMU

 

[alexcagle]

I use my fingernails and slide the cylinder on at a very slight angle most times.
Flat bottom cylinders are tricky when using only motoseal. It's difficult to keep the second ring from touching the motoseal once the cylinder slips on the first ring.

 

[tacomatrd98]

I use my fingernails and slide the cylinder on at a very slight angle most times.
Flat bottom cylinders are tricky when using only motoseal. It's difficult to keep the second ring from touching the motoseal once the cylinder slips on the first ring.

Put the sealer on the case side. Hold the piston skirts with your fingers and pinch the ring compressor with your thumb and index finger on that hand. Use you other hand to set the jug over the piston and slide it all together. This way you can use a regular ring compressor and not worry about smudging the sealer.

 

[a. palmer jr.]

I use an old radiator hose clamp for a ring compressor. I took the screw part off of it by cutting it down with tin snips and bending the ends so I could squeeze it with my fingers.

 

[ChoppyChoppy]

I've always installed them by hand. Once in a while it almost takes 2 people, but usually it's pretty easy. The 1 ring saws even easier.

 

[ELECT6845]

Is it possible you took 1.2mm rings off and you have 1.5mm rings your putting back on?

 

[cedarhollow]

Sounds like a tight fit not very much wear, good things, and lots of good ideas for ring compressors

 

[a. palmer jr.]

You can always try to put the top ring into the cylinder without the piston and see if it will fit. It should have a slight gap.