90.5mm vertex new ring end gap .022

[seanmx57]

I'm getting ready to put my motor together. I figured I'd check the ring end gap. I have a single ring vertex piston. I have 3 rings. One w/ about 10 hours on it and 2 new ones. The first new one was I think for a standard bore. The gap was big enough to throw a cat thru, like 1/8", I didn't bother to measure it. Next new one measured .022". The used one was .022" as well. My manual says the service limit on the honda rings is .020.

Should I run rings this loose? I have a feeling that ordering more new ones won't help unless I get them for a 91mm bore and grind them myself. I've never done this so It's not familiar. Anyone ever have this problem? I was getting 140~ PSI before the tear down with a stock head.

The bore is a fresh nikasil job that powerseal usa did o a stock sleeve. The piston to cylinder clearance is .003

All this is the stemed from a crappy bore job. The guy that did it didn't relieve the bridge. This created some premature wear during the 10 hours. I had the piston coated as well to bring everything to better than new standards. I have only been on 500's for 8 years and didn't know the bridge needed to be relieved. I never bothered to buy a manual because I've rebuilt my small bores so much in the 80's and 90's. If it wasn't for you guys I would have never know about the bridge goof.

[ISBB]

my rings were gapped at around .022 and running just fine.

Just my 2 cents. Its a 2 stroke it has 2 sealing rings.. its still gonna build pressure. Do a compression test after you get it together and see how it is and go from there.

[seanmx57]

my rings were gapped at around .022 and running just fine.

Just my 2 cents. Its a 2 stroke it has 2 sealing rings.. its still gonna build pressure. Do a compression test after you get it together and see how it is and go from there.

Was that on a vertex piston?

2 strokes can have one or 2 rings. Never seen em with more.

The point is having decent compression for a long time, thus the nikasil and coated piston. If I'm allready past the service limit before throwing together It isn't gonna get better is it. The coating is not the stock crappy break in coating on a vertex. Swaintech did the dome and skirt.

[iggys-amsoil]

Personally I wouldn't use a one ring piston unless it was a strickly race motor and plan on rebuilding at the end of the season.

I would be making a few phone calls on getting a replacement ring thats within specs. and order a couple of 91mm rings, then set the gap to .014-.016.

[seanmx57]

I plan on getting back into racing soon. I don't remember getting a choice on the number of rings on the piston when I bought it. Regardless I'm into it full bitch now, I had STR balance/rebuild the crank with a new pro-x rod set up for this piston, nik job, coated and all. I wanna run it till I get a compression drop. I even bought an hour meter so I can be scientific about the deal. Shoot I even switched to 927 not that I was having problems with synthetic oil, but I'm interested in running pretty crisp jetting and I think 927 will be my best bet in that regard.

[AlisoBob]

Your fine with the ring gap... no worries.

I wouldnt worry about an hour meter either..... just track how many gallons of gas you put through it .

Sound like you made a big investment in making sure the bore was round, and the nikisil plating wets out real nice with premix... that single ring Vertex should last quite a while....

My 2 ring Vertex set up is 3 years old... No sign of losing compression.

Sounds like your got the hot set up , well in hand.

http://www.bannedcr500riders.com/board/ ... php?t=1629

[100hp honda]

seems like my latest re-build is around .018 on the rings, honestly .022 would be a tough call for me but i personally would get a new ring, but thats just me. if you have the itch to ride it ASAP then you probly be ok, but if you could wait a week for a new ring then personally thats what i would do. remember, the gap will only get bigger as the bore wears, you do have nikisil so that will work in your favor. but, if you read any service manual for pretty much any dirtbike manufacturer, regardless if its nikisil or non-nikisil, .022" is on the large end of the spectrum before replacement is necessary.

flip a coin if you cant decide

heads= you run it
tails= you dont

[seanmx57]

If that .022 is OK why does honda say it's no good at .020? "no worries" maybe I'm too AR but with a single ring I would benefit from a more technical explanation. The main reason I went thru all this is longevity. I don't expect piston or cylinder wear for a decade but ring wear ... don't want to change em prematurely.

I see you are running a scalloped bore. 89.25 maybe? Were your rings this loose new?

X # of gallons = loss of compression = re-ring

Who knows what X =.

Is that the idea?

The hour meter is more for other log book stuff, I don't care about recommended service intervals. Compression tells the truth.

[seanmx57]

seems like my latest re-build is around .018 on the rings, honestly .022 would be a tough call for me but i personally would get a new ring, but thats just me. if you have the itch to ride it ASAP then you probly be ok, but if you could wait a week for a new ring then personally thats what i would do. remember, the gap will only get bigger as the bore wears, you do have nikisil so that will work in your favor. but, if you read any service manual for pretty much any dirtbike manufacturer, regardless if its nikisil or non-nikisil, .022" is on the large end of the spectrum before replacement is necessary.

flip a coin if you cant decide

heads= you run it
tails= you dont

I'm not in a hurry. I built a Nice CR250 to get into shape on in the spring, I got about 20 lbs to work off and I need some decent arms to hold onto the 500 now that I'm not riding daily anymore.

gotta call and see if I can swap them out. They messed up on one for sure.

[100hp honda]

seems like my latest re-build is around .018 on the rings, honestly .022 would be a tough call for me but i personally would get a new ring, but thats just me. if you have the itch to ride it ASAP then you probly be ok, but if you could wait a week for a new ring then personally thats what i would do. remember, the gap will only get bigger as the bore wears, you do have nikisil so that will work in your favor. but, if you read any service manual for pretty much any dirtbike manufacturer, regardless if its nikisil or non-nikisil, .022" is on the large end of the spectrum before replacement is necessary.

flip a coin if you cant decide

heads= you run it
tails= you dont

I'm not in a hurry. I built a Nice CR250 to get into shape on in the spring, I got about 20 lbs to work off and I need some decent arms to hold onto the 500 now that I'm not riding daily anymore.

gotta call and see if I can swap them out. They messed up on one for sure.

are you sure you ordered the right size ? the only reason i ask, i mistakingly ordered the wrong size once . took me a while to figure out why the gap was 2x larger than it should of been

[AlisoBob]

The hour meter is more for other log book stuff

Like what? Adjusting the valves?

[AlisoBob]

Wow. heres a blast , from the past..... Looked up some old photos...

The piston: Its a Vertex, and looked pretty good. The pin is tapered like stock, but tapered a little more. I dont have a scale, but on a balance beam, it was a little lighter than stock. The piston had alot of rough spots on the underside. EVERY rough spot / sharp corner is a potential place for a crack to develop. I took some time to conture every place on the underside.. see the photo. I think this will help somewhat in preventing the skirt damage that has been so widespread.



This looks MUCHO better


Then comes washing out the jug. I have seen guys wipe it out with a dirty rag, and think they are good to go... wrong.

The machining process leaving a great deal of micro particles, all of them quite abrasive. First with hot water and soap you scrub....and scrub.... until you are sure everything is clean. Then while it is still wet, hose it off in "PAM".. that kitchen cooking "non stick" stuff. Heres the ingredients....

Canola oil ( no rusting), Alcohol ( cleaning ability), Lecithin ( the non stick part, found in soy and castor beans). Its the perfect stuff, and you can use it in the house without the wifey freaking!

Spray / Wipe the cylinder several times... it will surprize you as to how black the paper towel will be after all your scrubbing efforts.... continue untill clean.

[100hp honda]

should of had them set the clearance at .002". i think you would be alright with that vertex and would probly be along time before it would need a rebuild. ive heard people say they set some bigbores a hair under.002 and it works tits, but i guess you have to be real careful during break-in.

[seanmx57]

The hour meter is more for other log book stuff

Like what? Adjusting the valves?

Yep, I adjust my widget valve and muffler bearings every 2.5 hours unless it's a full moon.

I wanna keep track of my hours on the motor. Hours on chains, tires suspension, etc.

At the moment, I'm particularly interested in how long I can go with out my tongue hanging out and flipping around like a rag dog. Pretty these days.

Good tip on the pam.

The rings I ordered were the right rings, I definitely got one that was not the right one. The other, who knows, the label said it was right, but .022 uhg.

regarding clearance of .003 I can adjust the clearance with the PC-9 skirt coating thickness. Swaintech will redo it thicker if I need it. Gonna put some hard hours on it and see how it is at .003. I doubt I will want it tighter, it's not like it's gonna wear and get sloppy.

[seanmx57]

OK Bob you win

Got off the phone w/ vertex tech support. They said for THEIR piston a .0065" per 1" of bore is the tightest the ring end gap should be. That equates to .023" so I'm good at least on the one correct ring. The big # was .008" per 1" of bore. The tolerance doesn't matter for single or double ring, same for both.

[AlisoBob]

OK Bob you win

I didnt win anything.... I just gave you my opinion....

YOU chose to do some more investigating, and came up with the answer YOU are comfortable with......

You couldnt have done it any better...

This site is not about being a herd of sheep.... its about finding things out for your self, and doing things your own way...

Well done Sean.....

[seanmx57]

OK Bob you win

I didnt win anything.... I just gave you my opinion....

YOU chose to do some more investigating, and came up with the answer YOU are comfortable with......

You couldnt have done it any better...

This site is not about being a herd of sheep.... its about finding things out for your self, and doing things your own way...

Well done Sean.....

Hey you got a point there. Thanks. I dunno why vertex specs are so different, but I'm not going to reinvent the wheel today.

[AlisoBob]

I dunno why vertex specs are so different...

Because the material is different than what Honda uses....

Different material = different expansion rates = different clearances....

[100hp honda]

vertex must use a different material aparently. .022" would be at the end of service life on honda, wiseco and ktm. i would of never guess the normal gap spec would be that large. just for the hell of it, if you happen to encounter problems, keep us posted.

[seanmx57]

I got the replacement ring today for the one that had the huge gap. I was excited because that means I can verify I got the right one and slap the head on. Well as I went to put it in I realized that I don't remember checking for the little 0 or o on the ring when I installed the .022 gapped ring

So the big ? what will happen if it is in upside down?

I once rebuilt my 1986 CR125 and just as I finished up I realized that I did NOT put the circlip on the piston that holds the wrist pin in. That was close.

The replacement ring was .022 as well.

[AlisoBob]

So the big ? what will happen if it is in upside down?

It wont seal for shit.....

Take it apart again....

[seanmx57]

man U R fast. I got the idea of bringing it to TDC and using a magnifying glass and a flashlight to look down as the head was still off. I did it right. Just couldn't remember checking for it. The o goes up right? LOL

Back to the basement.

[seanmx57]

OK Bob you win

I didnt win anything.... I just gave you my opinion....

YOU chose to do some more investigating, and came up with the answer YOU are comfortable with......

You couldnt have done it any better...

This site is not about being a herd of sheep.... its about finding things out for your self, and doing things your own way...

I'm a good student, I don't mind being in a herd if we have good teachers and the sheep are NOT wearing lingere . I thought I knew quite a bit about bikes untill I found the 500 forums. I've learned a ton of helpful info. I was spending a lot of time trying to figure out the same stuff that the guru's all know as common knowledge. It's very nice to have the voice of experience lighting the way sometimes.

The good news. I did a compression test last night. This is a nikasiled iron bore that was done with a torque plate to get a ROUND bore. I got 163 ~ 164 PSI on a stock 2000 head with a decompressor valve before the motor has even been started on a single ring vertex piston.

It turned 135 PSI with the decompressor activated.

Tomorrow I'll be jetting her for the CR250 igniton, hopefully it goes well.

I just modded the float bowl on the 38mm PWK so I can change the pilot jet without pulling the carb so it should be a joy compared to what I used to have to do. Pulling the subframe to to it blows.

[AlisoBob]

I've learned a ton of helpful info. ...... It's very nice to have the voice of experience lighting the way sometimes.

Nice job on the round bore...

[CR500R7]

It is very nice to have the voice of experience lighting the way everytime, not just sometimes!