Vertex Piston rings q
 

I bought and installed a new Vertex piston and rings on my 05 gasser.

The bike has about 4 hours of actual engine run time with the first couple real mellow break ins.

I started by warming it up for about tem min. and then shut it down for the night. I repeated this again the next night. On the next weekend, I went for a nice mellow ride and shut it down after about 20 min, and allowed the engine to cool completely. I did a little faster high RPM riding and allowed it to cool. When I put it away the timer had 1.7 hours on it.
I did go to the local MX track, but I had the flu and went home after only a half hour of riding.

Today at 3.7 hours, she stopped running altogether:eek: !! A compression test indicated that I had about 90 lbs. (should have 150 lbs.). I removed the head and found scarring by the exhaust port.

While I was doing my top end (a couple weeks ago) I noticed that the piston rings each had a small "N" stamped on the ends. I wondered breifly if they were supposed to be on the top (facing up) or on the bottom (facing down), but I went ahead with the project.

Now I am wondering if I should have paid more attention to that little "N". I called GoFasters and Mark said he would research it with his Vertex vendor and get back to me.

Does anyone here know about this ??:confused:

The "n" faces up to indicate the notch in the ring.

Here's generic 2 stroke piston showing the notch in the ring end.
http://upload.wikimedia.org/wikipedi...ngs.jpg/250px-

I don't recall if the Vertex rings have that notch or not.

By coincidence just been speaking to my dealer having had my cylinder returned from replating. He said they use the contractor they do because they do a good job including chamfering the ports so the piston doesn't catch when there's wear.

Might be worth checking? Although the piston is new if the cylinder is worn just perhaps it wobbled enough to catch?

It's hard to put the rings on wrong because of the locating pin it should be obvious which way is up. However ... you can put the piston in wrong. There should be an arrow on the crown pointing forward. Although I would've thought getting that wrong would result in instant failure. The piston must be oriented so the ends of the rings cannot flick out into the ports.

Apart from that maybe it was a "normal" seizure - too lean, too cold, no oil etc etc

When I put in Vertex rings, there was no difference between the top and bottom of the ring. They look/fit the same either way.

Did you check/set the ring end gap? Typically the ring end gap is too small and the ring ends need to be filed to meet the GG engine manual spec. (Check GG manual on line)

Assume nothing and take nothing for granted. You absolutely have to measure both the piston and the cylinder.I have a freshly plated 200 jug that was done in conjunction with the B piston that was provided as a reference, the outcome 3.5 thou piston to wall clearance, now I'm looking for an E or F piston to correct the clearance surplus. I have also seen brand new off the shelf KTM 200 pistons out of spec and unusable.Do yourself a favour do it once but do it right! I once srcewed up a perfectly good kx cylinder partly due to undertaking the job after consuming copious amounts of good European beer. I was going to re ring a vertex piston using non vertex rings. I measured the end gap which was ok then I went ahead and miked the ring thickness ,ok no prob same a vertex, then I had a couple of more ice cold Becks. What I neglegted to do was to measure the new rings depth in the ring land, they looked ok to through my beer googles no prob, fifteen minutes later after breaking the top end in, in the back alley a mysterious loss of compression resulted. End result and a screwed cylinder. All I can say is good thing I did'nt go to the bar lookin for company!

Sounds like you put the piston in backwards....... the arrow on the top of the piston should point to the exhaust.

The ring end gaps should be on the intake side of the cylinder, if you hooked a ring end-gap in the exhaust, the piston was put in backwards.

Also, maybe a piton pin clip came out, they can be hard to get in and it takes some experience to know when they are seated properly.

JMO, Ron

The Rub...
 

The whole front of the piston is rubbed off, right over the rings and everything !! The rub is about 11 thousanths of an inch deep and extends down the piston from top to the skirt and about 2.75" along the front circumfrence.

The arrow was pointing the right direction (forward) and both of the rings gaps were over the nubs in the groovs as shown in a previous post. Both piston pin clips were properly seated, in place and in tact.

The wrist pin was a major Bi#*h to remove. It was in there way way tight. It installed real nice !! I used two stroke oil on all of the assembly locations (wrist pin, & bearing, and both rings). The little "N"s stamped into the ring ends are both facing up (but I am told it doesnt matter).



RBD Ron, do you do sleaves or Nickl-seal ??

You did't mess up putting your powervalve in wrong did you?

I know what happened now
 

It wasnt the PowerValve either. I never removed it.

I didnt really think of it at the time (last night), but I remembered (this afternoon) that as I was removing the forward base nuts, they seemed to come off way too easy.

I think I had an air leak in the front base gasket and that is what burned up the front of my piston. I just didnt have the nuts torqued properly.

Now Im gonna upgrade to a 300 jug from GoFasters and chalk it up to an expensive lesson learned. My origional jug is a complete loss. It has a big crack that runs horizontaly between the exhaust port and the PV barrol bore.