Is it possible to replace a piston's ring pin?
 

Hi all. I was wondering if it is possible to replace or repair the ring pin in a piston's groove. I have an old piston that will be difficult to replace. It is in very good condition except that the ring pin seems worn down to the point that it doesn't hold the ring in place.

Thanks,
David

RE: Is it possible to replace a piston's ring pin?
 

In the type that protrude into the ring groove in a horizontal manner and their length set radial to the bore in that they extend from the bore exterior to the bore center, if they are not in a "blind pocket", can be driven through to the inside of the piston by a new sprig pin.

Ones in blind pockets, if you cannot pull them out, they cannot be replaced.

There are the type that are drilled vertically from the piston top that are generally in a blind pocket

The new pin can be placed in an alternaye location.

RE: Is it possible to replace a piston's ring pin?
 

Thanks w8ye. This one is inserted horizontally into a blind pocket. I guess I could file the old one down and drill a new hole. The problem will be finding a spring pin that's small enough.

David

RE: Is it possible to replace a piston's ring pin?
 

If you or a friend has a mill, you can use a milling bit just wide enough to mill the pin off. You can drill a hole for a new pin, but make sure the end gap does not line up with a port. Capt,n;)

RE: Is it possible to replace a piston's ring pin?
 

Be very carefull not to file on the ring grove land. The land has to be very good... to seal the ring from blow-bye! Capt,n

RE: Is it possible to replace a piston's ring pin?
 

As the Captain said, the ring gap can be on the opposite side as long as pin places the the ring gap between ports.

RE: Is it possible to replace a piston's ring pin?
 

Yep, it will be tricky to file down the pin by hand without cutting into the ring groove. I may just wait until I can find another piston.

David

RE: Is it possible to replace a piston's ring pin?
 

The pins are usually what is called a spring pin and the are hard. They will ruin a file or end mill

RE: Is it possible to replace a piston's ring pin?
 

If you can find a small machine shop that will do what we used to call "government work", they may be able to use a Wire EDM to burn the pin out without causing any problems with the ring seat. The wire EDM machines are not difficult to build, but they would cost you way more than a new engine. If you can find a machine shop that has one, they can save the piston for you. The machines were first designed to cut part from a carbon pattern, then the wire part came into existance and they were able lto CNC cut stuff with great precession. Small shops will have one to save work that has a drill or a tap broken off in it. They can cut to under 0.001" tollerance and easilly remove a broken drill or Tap, or in your case a damaged/worn spring pin.

Good luck with your project.

Don

RE: Is it possible to replace a piston's ring pin?
 

w8ye, and captinjohn are right on the money. I like campgems idea the best. There are some real sharp people at a company name Powroll. They are high performance motorcycle machineists. Check them out on the Internet. They are located in Oregon and their work is superb. I haven't seen a pinned piston ring since the last two cycle motorcycle I repaired. You must have some really wild and large intake and/or exhaust ports in that engine. May I ask what engine make and size you are repairing?

I don't think it's out of the question to locate another piston of similar enough dimensions to have it machined into spec by a good machine shop. Look for an engine of similar bore and stroke. If the replacement piston doesn't have a pinned ring so much the better because it would be easy for a machine shop to drill and press-fit a piece of hardened piano wire into the new piston to pin your ring. If you can't locate a new piston what are you doing for a piston ring? Have you thought about searching for a "parts" engine on eBay?

An old hot rod auto saying "Speed costs money, how fast can you afford to go."

Good luck,
Bill

RE: Is it possible to replace a piston's ring pin?
 

Put the ring on the piston and insert the piston in the top part of the sleeve. Now rotate the rod/piston. Does the ring rotate with the piston. If it does, you don't have a problem.

As others pointed out, make certain you don't line up with a port doing this. You will break the ring. Don't ask me how I know.[:@]

What does the relief in the ring for the pin look like? Is it knackered or in near new condition? If it is worn and shinny, your engine probably has some run time and the pin and the ring have been "worried" to uselessness. If this is the case I would be very careful of just pulling out the old pin and inserting a new one. The same "working" of the pin that damaged it could have damaged the hole it is mounted in. If the ring gap is pristine, someone in the past has probably assembled the engine without lining up the pin and ring gap and forced the pin deeper.

Bill

RE: Is it possible to replace a piston's ring pin?
 

Thanks everyone. I have a new ring on the way from Bowman (might get here today). I will do the test to see if the new ring slips when the piston is rotated in the sleeve, or stays in position. I picked up another, used .60 FSR, so that's what this piston if from.

I'm assuming that it doesn't take too much pin area to keep a ring in place. I can't image there being a lot of rotational force on a ring when an engine is running. Isn't most of the force up and down?

Thanks,
David

RE: Is it possible to replace a piston's ring pin?
 

That is correct

RE: Is it possible to replace a piston's ring pin?
 

Hey David. There's a possiblity for a new replacemant piston. I did as much research as I could on os replacement pistons and sleeves. This piston might work as replacement, would have to compare with someone that already has one or just outright buy it. Remember, I'm not sure it will work. Tower lists it withthe same dimensions as the 60 and 61 FSR piston OD 24mm and it takes the same ring as the 60 FSR and 61 FSR

1. OS 61 SX-H piston 27903200 http://www3.towerhobbies.com/cgi-bin...&I=LXCS59&P=SM

O.S. Piston Ring 60-61 26703404 http://www3.towerhobbies.com/cgi-bin...&I=LXCT22&P=SM

Bryan

RE: Is it possible to replace a piston's ring pin?
 

Thanks Bryan. I found a vendor who's selling the SX-H piston a lot cheaper than Tower, so I bought one. The bore is correct - 24mm - I'll have to wait until it arrives to see if the wrist pin is the same diameter. If not, then I would also need a new pin and conrod, assuming that the crankpin is the same diameter.[sm=bananahead.gif]

Another thing to find out is if the ring pin in the SX-H piston lines up with a bridge between the ports in the FSR sleeve.

David

RE: Is it possible to replace a piston's ring pin?
 

Don't forget to check to see if the wrist pin is in the correct position in the piston. The distance from the pin to the piston crown defines the head deck height.

Bill

RE: Is it possible to replace a piston's ring pin?
 

Use a peice of soft clay or solder to check clearence with the piston at top Dead center. Capt,n

RE: Is it possible to replace a piston's ring pin?
 

So, I should put the clay along the edge of the piston so it is squished by the Squish Band, correct?

David

RE: Is it possible to replace a piston's ring pin?
 

Hey rainedave. I forgot to mention it above.

The SX and RX ringed pistons also take the same piston pin as the 60-61 FSR's an the VF. What I don't know is if the location of the pin bore in the piston is the same. Also for the SX RX conrod is the same length as the FSR-VF, but the hole for the crank pin is 0.5mm larger. You could possible use the SX-RX crankshaft and conrod but you would have to take off 1-2mm around the counter weight to get it to fit in an SF-RF case (1mm) or FSR-VF case (2mm). I already have a SX-RX crankshaft that I'm going to modify to tryout as a replacement as the bearing surfaces are the same as SF-RF and FSR-VF. But have to find someone with a lathe to do it.

Here's the link for the piston pin this would also work in the SF-RF but you would have to grind off one end to get the pin clips on.

http://www3.towerhobbies.com/cgi-bin...6007&search=Go

RE: Is it possible to replace a piston's ring pin?
 

So, if the wrist pin is the same diameter, then I should be able to use the FSR conrod, correct?

David

RE: Is it possible to replace a piston's ring pin?
 

Yes, it's the same diameter. The conrod is the same on both the 60FSR and 61FSR. But again the location of the piston pin bore ON the SX piston is what I don't know. I bought a SX conrod and crankshaft outright just to see what was different.

Hey check out the other post you started http://www.rcuniverse.com/forum/m_8127063/tm.htm

I listed a bunch of info on these engines.