Take care of your Big Bore

:-/ a .020" cutter?

What's holding the alignment pins in anyway? Good old fashioned pressed fit?

I wonder if you can bake the piston and get them to fall out without ruining anything. You'll destroy that piston if you catch one of those and I'm not sure you can work the groove out far enough by skirting around the pin to get the wiseco rings to seat into the ring groove.. I don't know, maybe. I'd have to be standing at the lathe to figure out how you're going to work around the pins.
 
No lathe involved. The piston will rest on a "V" block and a positive stop and be turned by hand. I'm not crazy about pulling the pins out and putting them back in. I don't want them to fail. I've got a bunch of old pistons I'm going to try this on first. I'll see how hard it is to get the pins out.
 
just a word of caution ,not saying it wont work but taking those alignment pins out is asking for big trouble in my eyes ,once they are removed you could alter the fit and risk them coming out under pressure .big bore kits arent cheap and one of those coming out at high rpm could be disastrous. personaly i dont have a problem with the wossners ,built alot of big bores using them since they came out .wiseco stopped making the 72mm so youll never find one .forged vitos big bores have that pie cut in the exhaust area that throws off the port timing and increases your blowdown duration,not something desirable on an already ported cylinder .back in the day alot of bikes used just one single ring,keep in mind if the bore was loose from the factory or your crank had issues that could have caused excessive ring wear on those rings that freek described and if memory serves he had ken mod/repair his crank becuase of some issues it had over the summer ,i would take a wossner over vitos anyday of the week,if you are die hard determined you could use a H2 piston form the old kawasaki triple also in a pinch you can re-ring a wiseco 72mm using ktm rings,their are other ways to cheat it
 
FLOTEK said:
just a word of caution ,not saying it wont work but taking those alignment pins out is asking for big trouble in my eyes ,once they are removed you could alter the fit and risk them coming out under pressure .big bore kits arent cheap and one of those coming out at high rpm could be disastrous. personaly i dont have a problem with the wossners ,built alot of big bores using them since they came out .wiseco stopped making the 72mm so youll never find one .forged vitos big bores have that pie cut in the exhaust area that throws off the port timing and increases your blowdown duration,not something desirable on an already ported cylinder .back in the day alot of bikes used just one single ring,keep in mind if the bore was loose from the factory or your crank had issues that could have caused excessive ring wear on those rings that freek described and if memory serves he had ken mod/repair his crank becuase of some issues it had over the summer ,i would take a wossner over vitos anyday of the week,if you are die hard determined you could use a H2 piston form the old kawasaki triple also in a pinch you can re-ring a wiseco 72mm using ktm rings,their are other ways to cheat it
Click to expand...

good call denny, i shouldnt have bashed on the wossner when yes i did have a crank issue that caused the premature wear on the rings...my concern is the ring thickness....doesnt seem like they will last too long

and awesome info on the little secrets brotha......i knew i shoulda pm'ed ya first lol
 
I messed around with the set-up yesterday. I started looking at some old tooling we had and figured it would take hours to make all of it work to cut ring grooves. I also took a look at the pins in an old Wiseco piston. The pin has enough room between it and the bottom of the ring groove to get a cutting tool in without taking the pin out. I was also able to get a piston mounted in the lathe and indicated to .001 run out with a three jaw chuck. I know I can get it closer with a little more time. I measured what was left of the piston skirt before and after it was chucked and there were no changes in diameter. I left the special cutter we made at work on Friday so I'll have to wait to see if the process will work. The only thing I'm concerned about is the deflection of the cutter and nothing moving once the cutting starts.




 
Last edited by a moderator:
Is it really needed? The thread started off with doing some Wossner bashing but I need to hear from more people having problems before I make a decision. Denny at Flotek said he has'nt had any problems with the Wossner piston or their rings. I have alot of respect for Ken Oconnor and appreciate him doing stuff like this but is it really needed. You guys are smarter than me and know best, I just need to hear of more failures before I spread the word that their junk.
 
I decided to work on this more today. I started measuring a bunch of pistons and found that the one I mounted yesterday is not a Wiseco piston. It's a cast stock piston. The pins in the Wiseco fill the entire groove so the tool I made won't work if the Wossner piston has the same set up as Wiseco and I bet it does. I've never used one so I won't know till it gets here. I'm going to cut the stock piston for the hell of it and will post a vid later today. I would rather run a 1mm ring over a .75mm if it's possible.
 
I was wondering what good a V block would do and why you wouldn't just chuck it up and see what you had but after you said "no lathe" I kept my mouth shut...

I was thinking that the wiseco ring pin filled the entire groove which is why I asked how you were planning to extract it before you turned out the groove.

It's still possible to turn the groove out without pulling the pin while using the tool you've already made. The factory pin comes all the way to outside but only take up half the groove. The wiseco pin takes up the entire groove (height wise) but only comes out halfway to the bore. You can start turning the groove out on the very outside edge of the piston ring groove to make sure you're going to clear the alignment pin and then move the cutter inwards under the pin (staying in the aluminum skirting just under the pin) while it's still in there. Once you've got the groove cut under the pin deeper the wiseco rings should use the pin for alignment even though they'll only use the top .75mm and there'll be a small gap under the alignment pin where the ring will have a groove for the pin but there won't be any pin there. No biggie for an experimental engine anyway...
 
The ring groove is .042 “ and the pin is much larger and extends into both the top and the bottom of the ring groove. The only way to do this correctly is to remove the pin and start cutting. I'm on the band waggon of not to pull the pins. No way to do it accurately with the pin still in the hole. I'll cut my losses and run the stock Wossner rings and change them as needed. Still want to post the vid of cutting the stock piston but I'll do it later. I'm beat!
 
I didn't realize the wiseco alingment pins went above and below the ring groove. Oh well! Wossner does seem to have a good reputation for quality pistons even if they might require a rering more often.
 
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