help! the MOST diffcult piston swap I have ever..

[MN_Kevin]

I am STRUGGLING to get this WISECO 420 piston into my recently bored and replated engine.

I have done hundreds of top ends (2 and 4 stroke), but this thing is killing me.

The problem is the wiper(?) ring >> the "accordian" ring including it's two flat rings.

NOTE: this is NOT the two compression rings.

I have installed the piston into the cylinder w/ the accordian ring by itself >> it fits.

I have installed the two flat rings, MINUS THE ACCORDIAN RING >> they fit (end gap is zilch though)

I put all three in the slot >> FORGET IT.

I cannot get the flat rings to close up their end gap w/ the accordian ring installed. The accordian rings overlaps itself at it's end gap, making installation impossible. The accordian has a little lip on the inner side of it. The flat rings push against the lip FORCING the wiper tight into the piston. I thought of a ring compressor (NEVER had to use one) but I don't think it would work on this cylinder.

I could use maybe 2 "C" clamps, offset by 180 degrees to hold everything tight, then remove one of them. The other would be aligned w/ the (2) dished out portions on the cylinder liner edge. As I insert the piston into the cylinder, and the wiper makes it into the beveled edge of the liner, holding everything tight, THEN remove the final "C" clamp...???

I am open to EVERYTHING and ANYTHING, including doing shots of Absolute Vodka to make me feel better (I have a case of Sam Adams as well).

[Indy_WR450]

Food for thought only. Try a large adjustable hose type metal clamp. tighten around flush with the first ring and using a rubber mallet tap the piston into the piston sleeve leaving the metal clamp outside of the piston sleeve.

[YZ400Court]

The oil ring DOES NOT overlap. It butts up end to end and the wipers kinda squeeze it into place. I had the same problem with the 420 piston with the bored cylinder, I even ended up ruining one of the wiper rings by forcing it and bending it. It is a real pain as some of the bevel was bored out at the bottom of the cylinder. Did you check end gap on the wipers? Patience is the key, and a ring compressor might help (i too have never used one).

[MN_Kevin]

The oil ring DOES NOT overlap. It butts up end to end and the wipers kinda squeeze it into place. I had the same problem with the 420 piston with the bored cylinder, I even ended up ruining one of the wiper rings by forcing it and bending it. It is a real pain as some of the bevel was bored out at the bottom of the cylinder. Did you check end gap on the wipers? Patience is the key, and a ring compressor might help (i too have never used one).

EXACTLY!!

You know my pain!!

wiper end gap is almost ZERO >> 0.1 - 0.2 mm

I'll keep pluggin' away at it but I am ready to start drowning my sorrows!! ?

[KiwiThumper]

I have installed the two flat rings, MINUS THE ACCORDIAN RING >> they fit (end gap is zilch though)

You definately need to have some end gap. If there is none, the rings WILL bind in the cyclinder when they heat up. IMO

[beezer]

I use an auotmotive ring compressor to install Wiesco pistons.

[chabon99]

I had the exact same problem. My solution: take it in to the shop, pay them .5 hr labor to put the piston in the cylinder, take it home and finish the job with a smile on your face.

[yamaha.dude]

I think you need to have some end gap... as long as the two wiper rings are offset, then the cylinder will be wiped properly, even with a reasonable gap in the two of them... the 'wriggly' one is there to keep them apart and under tension... but it should not overlap itself either... that will fill the ring groove and make the wiper rings bind at that point...

I think the answer is to open up the gap on the two wipers and to have a small gap on the 'wriggly' one as well...

HTH, YMMV, JMHO,

David

[BEAN329]

You ALWAYS check end gap on ALL rings Before install. I don't care who tells you any differently. RTFM on end gap spec's thats why they have them. Yes some cylinders can be more of a pain in ass then others. It's usually because when you bore a cylinder you lose the taper at the bottom of the cylinder. Like the other person said, be patient.

[MN_Kevin]

It has crossed my mind to clip one "link" off of the accordian ring. It DOES stretch and should(?) work...

[Wayward Son]

do not clip the expander!it will smoke for sure!use the big hose clamp!it will work!

[SFO]

I have had to adjust the ring end gap on most of the wiseco kits I have installed.

They give a value of like .004" per inch of bore.

This is printed on an orange piece of paper and included in the piston or ring package. This piece of paper also has the expander ring detail on it.

I noticed the same difficulty with the installation and it is due to the chamfer not being enlarged with the overbore. I believe the wiseco ring pack has more tension than the oem yamaha and both these details conspire to make the assembly challenging for even an experienced mechanic.

I would verify all my end gaps before going any further.

[Hick]

The Wiseco 97 mm piston kit I put in my '00 had the same problem. I gapped the compression rings and the top one was way too tight. I too could not get the oil rings on. It's a Wiseco thing I guess, but they went right in after I gapped them also.

[RCannon]

I would recommend drinking more. It wont help the bike, but you'l no longer care.

[SUnruh]

kevin,

since i just did this on my 262, i know EXACTLY what your problem is. ?

you must, i repeat *MUST* put the waffle ring on first. then the 2 wiper rings. the waffle ring will NOT have any end gap. the wiper rings should spec out around 0.22 or so gap. wiseco says to have 0.04 of ring end gap per 1" of bore on the 2 compression rings. it says this on the little orange sheet in with the rings. at least mine did.

once you get all the rings on the piston, here is where the REAL fun begins. getting the darn rod pin into the piston, while holding the cylinder with the piston down far enough to expose the pin hole, but NOT let the wiper rings pop out of the bore. it took me 6, yes SIX tries to get it.

steve

[MN_Kevin]

Steve,

For Better or Worse, Richer or Poorer, I CUT some of the spacer, ~ 1 "link".

I had ZERO problem putting it together this time. I was concerned I cut off too much, but the end gap closed up quite nicely.

As a caveat, the wrist pin and c-clips were missing out of the box... .

>> A quick call to Eric Gorr and my parts will be on the way tomorrow! ?