Changing piston rings...HUGE PAIN

I just tried to change my piston rings and even after reasing post and fred's guide I still can't get the piston in. It keeps getting stuck in one spot

I used oil and ended up snapping one of the rings (luckily I have extras) when I foolishly tried to rotate the cylinder on....I was just wondering if there was a best way to do this or any tools that could help?! Thanks!

-Evan

Re: Changing piston rings...HUGE PAIN

Richard Child /

Don't know what kind of Ped you have but on a Honda Express There are 2 tiny pins in the piston groves that the end of the ring has to butt up to. If you put the ring over the pin you will never get the piston in the cylinder.

Re: Changing piston rings...HUGE PAIN

you can put the piston into the cylinder from the top side and then push the piston down far enough to install the wrist pin and circlips if thats any easier. You can make many different ring compressor designs from steel can material. And for any of you who may not already know, it's bad form to install a ring onto the piston by puting one end in the groove and then rolling the rest of the ring into the groove. It puts a twist in the ring that causes it to bind in the groove and so the ring will not free float in the groove

Re: Changing piston rings...HUGE PAIN

Allen Murphy /

Crybaby got the right idea--I've used a hose clamp for a ring compressor to put the piston in through the TOP of the cylinder, and pushed it down to the point wheree I could put in the wrist pin.

Tastes great, less filling!

Al Murphy

Re: Changing piston rings...HUGE PAIN

hose clamps! Perfect! I was trying to think of anything that could compress the rings...I'll try it tomorrow. Thanks for the posts

Re: Changing piston rings...HUGE PAIN

Hose clamps? What are those?

I had a hard time installing the piston w/ rings on the cylinder.

I finally put it in out of proper alignement.

I had to do this in order to compress the rings with my fingers as I slid the piston onto the cylinder. I also cleaned my fingers with rubbing alchohol so they wouldn't slide off the lubed up piston and rings.

I then rotated the piston into the the correct position. Next goes the wrist pen and circlips.

Took me at least 2 hours.

good luck and post back what technique and tools you found useful for this hard and tedious task.

Re: Changing piston rings...HUGE PAIN

Allen Murphy /

Did it with hose clamps and took all of 5 seconds to slide in the piston from the top, in correct alignment even.

Slid it in from the TOP, pushed it so the skirt and wrist pin hole were showing, tapped in the wrist pin, and slid the cylinder down the studs to mate with the crankcase.

Use the screw-type hose clamps, and don"t be stingy with the oil on the cylinder bore. I used the handle of a hammer to gently tap in the piston.

Just like working on an air-cooled Volkswagen engine, but fewer parts!

Al Murphy

Re: Changing piston rings...HUGE PAIN

Al - thanks for the information.

Glad to hear you got your piston in and very quick.

I will remember the hose clamp trick for the future.

hose clamp?

I just don't understand how you can use hose clamps?

It seems like they would create too large of a diamter around the piston for it to go onto the cylinder?

Could you please explain in more detail how you use them or post some pictures?

Thanks.

ps> I have an old piston and rings; maybe I will buy some hose clamps and give it a try for practice.

Re: hose clamp?

you drop the piston into the cylinder, then you compress the rings with the clamp, line up the clamp with the bore and tap the piston down, works almost exactly like a ring compressor for an auto piston

Re: hose clamp?

Allen Murphy /

The trick is don't insert the piston from the bottom--insert it from the top. get your alignment correct so your rings don't catch in the ports, then push it out the bottom of the cylinder until the wrist pin hole is visible

Basically, what you're doing is installing the cylinder AND piston as a unit, all at one time!

I've got rings ordered for my Morini MO--I'll take pics when the rings come in.

Al Murphy

Re: hose clamp?

Nero, the hose clamp stays stationary on top the cylinder with the rings and piston sliding in it's inside diameter. The hose clamp doesn't actually enter the cylinder. When you try it you'll see

Re: hose clamp?

Thanks for everyones help. The main reason why the rings wouldn't fit was because there were the wrong size! Once I got the right size rings (the day it started to snow a ton) I used the hose clamp method and they went in perfectly.

Thanks

Re: hose clamp?

John Joedicke /

Also can use a zip ty, won't scratch the piston.

Re: hose clamp?

i bought the wrong size, and snapped 2, waste of money, i accidently bought OS wich i thought mean "original stock" but it meant "over size" when i put them on, i noticed even when totally cloded on the piston, it made to much space, im ordiring the right size tommorow.

Re: hose clamp?

Me too! I bought the oversized from mopedwarehouse.com by accident. I broke the oversized ones but once i got the right size they went right on.

Re: hose clamp?

Jamie Robinson /

I imagine you could buy a piston ring compressor from a small engine repair shop. Get one for a chainsaw or anything else with a similar piston size. They don't cost very much.

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