quick question on ring position on piston

Letters up is what I've always heard (and done). Not sure of the validity of it, though.

Letters deffinetly go up. Letters down creates too much crankcase pressure...(probobly not a real concern, but enough to be mentioned)

Rings are usually not cut perfectly square. There a many types, rings are designed to be installed in one position only. The rings are designed to moved in a certain direction when combustion occurs to seal the cylinder properly, yet not catch on the many ports cut into the cylinder. You are risking a lot by installing them backwards. The ring could break, and do some serious damage. More compression is not always better. It causes more heat as well as detonation. Increased wear on the piston, con rod and crank that may not have been designed to take the extra compression.

Keith

Installing rings upside down is bad idea. If its a keystone syle ring then its not going to fit inside the groove correctly and the clearances are going to be wrong. certain rings are made for certain types of pistons and you always put letters facing up.

my new rings didn't have any letters on them!!!! And they where original Honda.. I know for sure because i read about it, in this forum one time. So when i had to assemble my top end again, i took notice that i´ve heard about letters up on rings. But there were not any letters on the rings.!! strange!

Alright, this crap about building too much crankcase pressure if you put your ring on upside down is extremely humorous. A flat ring on a two stroke is just that, flat. The face is symetrical and does not care which way it is installed. Modern two stroke flat rings are not like modern 4 stroke rings, which have much more complicated geometry (twists, bevels, scraper faces, etc).

The semi-keystone ring is the only exception to this rule (in a 2 stroke). A semi-keystone ring has a 7 degree angle on the top surface and flat on the bottom. Though not as popular in the modern MX bike, the 2005 CR250 has a semi-keystone ring (single ring also). In this case, it is imperative that you put the ring in the correct way, markings up. In reality though, you would be hard pressed to even get it started in the cylinder if the ring was upside down, but I have seen people try.

The article that was mentioned (or implied) about building too much crankcase pressure (Dirt Bike or Dirt Rider last month, I am not sure which one), also had an article about rebuilding a YZ250F. In this article, they said that you must "overlap the spring thingy" on the oil ring for proper installation! The "spring thingy" is the expander of the oil ring, if you overlap the expander it will be a pain to install and if you do manage to get it installed the bike will smoke like a 2-stroke and eventually break the oil ring. The purpose of the expander is to apply a spring pressure to the two thin rails of the oil ring (which in turn, scrape the oil from the cylinder wall), if you overlap the expander, you will have eliminated the spring tension.

Alright, now that I am done ranting, it is a good idea to put marks up on a 2 stroke, but if the marks are not there, do not panic. You will not suddenly start supercharging your bottom end. The information put out by some of these magazines could be costly to a guy who actually follows their instructions.

Joe

yup what he said

I stated that all rings are not cut equally and that you are at risk of installing them upside down. I personally do not know for a fact that all 2 stoke rings are square cut as I have not inspected all the manufacturer's rings. If there are no markings then I would assume that the rings were square cut. As humourous as it seems, the question asked was valid. The answers given were also respectable.
Keith

Keith,
I didn't say the question wasn't valid, it was, I was saying that the concept that you will get increased crankcase pressure by installing a ring upside down is humurous.

Probably 80-90% (maybe thats a little high) of the readers of these mags don't know better. They are not shop owners or part of a race team or part of the industry, so when a magazine says something, they assume its credible (as they should be able to). In the case of the crankcase pressure, it was funny, not potentially a failure. The case of the oil ring, could be very expensive if someone followed the instructions of the magazine.

Forums like this are the perfect place for someone to validate the information, I am happy to be part of that. But I also challenge anyone to show me that you get an increase in crankcase pressure by installing a ring upside down.

Joe

All of the rings that I have ever installed in my 2-Stroke MX bikes haven't been directional, but the other day when I was installing new pistons on my snowmobile, I ran into a problem. The cylinder didn't feel like it was going on right. So I pulled it off and put some more premix on the rings and attempted again. Still no go! I then realized that I had the rings on backwards. If they are the wrong way they will bind and get stuck in the piston. I flipped them around and everything was back to normal.

Studboy, what ski do you have? Semi keystone rings are very common in watercraft, marine and snowmobile engines.

Joe