So long old friend...
So long old friend...
I was prepping my bike to go riding tomorrow and I had to change my jets from coming back from the summer at high elevation. So I also decided to take a look at the reeds and the piston to see how things were going. Here's what I found:
It was a Vertex. I had radiused the inside of the skirt before I installed it to prevent this sort of thing from happening, but alas it was not enough. Bob I don't know if you remember, but we had a discussion on the other board about this. Thinking of going to a Wiseco this time and having GSS do the work. Other than the crack, the rest of the piston looked good, no rub marks, only a little blow-by on the exhaust side. I'll probably strip it down tomorrow to get a better look.
Exhaust side:
It had been almost exactly two years of mixed riding since it was installed. I would guess about 75 hours, I dunno. Has anyone looked into nikasil or equivalent for the 500? I saw that US Chrome does this for iron sleeved cylinders, wondering if it was worth it.
It was a Vertex. I had radiused the inside of the skirt before I installed it to prevent this sort of thing from happening, but alas it was not enough. Bob I don't know if you remember, but we had a discussion on the other board about this. Thinking of going to a Wiseco this time and having GSS do the work. Other than the crack, the rest of the piston looked good, no rub marks, only a little blow-by on the exhaust side. I'll probably strip it down tomorrow to get a better look.
Exhaust side:
It had been almost exactly two years of mixed riding since it was installed. I would guess about 75 hours, I dunno. Has anyone looked into nikasil or equivalent for the 500? I saw that US Chrome does this for iron sleeved cylinders, wondering if it was worth it.
Yea.. cracked skirts are pretty common on cast pistons when the piston to wall clearence gets too big.
Scored pistons are pretty common with forged when the clearence is too small.....
Take your pick I guess.
My Vertex is getting pretty old. I'll inspect it pretty closely while the motor is out of the bike while doing the A/F conversion.
Most cracked cast pistons seem to happen after the first one has cracked, and a replacement piston is fitted without correcting the clearence issue.
Then its a cycle of crack, crack,crack... until the cylinder is bored, and the proper clearence is restored.
Two years of solid riding is a good lifespan, look at the "factory" maintenance interval, 20 hours or something like that.
If you buy a bike, the VERY first thing you should do is pull the reed block and pipe for an inspection, and count a top end into the price of the bike when you purchase, no matter what...even if the seller says its " Fresh"...
Ya, right....
Nikasil on a CR500 sleeve would be the hot ticket.
Do it!
Scored pistons are pretty common with forged when the clearence is too small.....
Take your pick I guess.
My Vertex is getting pretty old. I'll inspect it pretty closely while the motor is out of the bike while doing the A/F conversion.
Most cracked cast pistons seem to happen after the first one has cracked, and a replacement piston is fitted without correcting the clearence issue.
Then its a cycle of crack, crack,crack... until the cylinder is bored, and the proper clearence is restored.
Two years of solid riding is a good lifespan, look at the "factory" maintenance interval, 20 hours or something like that.
If you buy a bike, the VERY first thing you should do is pull the reed block and pipe for an inspection, and count a top end into the price of the bike when you purchase, no matter what...even if the seller says its " Fresh"...
Ya, right....
Nikasil on a CR500 sleeve would be the hot ticket.
Do it!
AlisoBob wrote:Yea.. cracked skirts are pretty common on cast pistons when the piston to wall clearence gets too big.
Scored pistons are pretty common with forged when the clearence is too small.....
Take your pick I guess.
My Vertex is getting pretty old. I'll inspect it pretty closely while the motor is out of the bike while doing the A/F conversion.
Most cracked cast pistons seem to happen after the first one has cracked, and a replacement piston is fitted without correcting the clearence issue.
Then its a cycle of crack, crack,crack... until the cylinder is bored, and the proper clearence is restored.
Two years of solid riding is a good lifespan, look at the "factory" maintenance interval, 20 hours or something like that.
If you buy a bike, the VERY first thing you should do is pull the reed block and pipe for an inspection, and count a top end into the price of the bike when you purchase, no matter what...even if the seller says its " Fresh"...
Ya, right....
Nikasil on a CR500 sleeve would be the hot ticket.
Do it!
Spoken like a true HOON!!!
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LIVIN THE DREAM!!!
NOTHING BUT GREEN LABEL BLENDZALL!!!
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So today I finally got around to stripping the cylinder. Got the classic stop sign going on.
Piston comparison, old 89.5mm Vertex with new 90mm Vertex. Shows the smoothing work that I did with the casting flaws on the inside. Did it work, I don't know, but I think that it helped, considering that BOTH of the rings gapped at over .035 (biggest that my feeler gages go). I think that I'll be doing this again this time, since I don't think that it could hurt.
When Maxima says that the 927 has a long residence time, they're not kidding, there was a puddle of it in the bottom.
Piston comparison, old 89.5mm Vertex with new 90mm Vertex. Shows the smoothing work that I did with the casting flaws on the inside. Did it work, I don't know, but I think that it helped, considering that BOTH of the rings gapped at over .035 (biggest that my feeler gages go). I think that I'll be doing this again this time, since I don't think that it could hurt.
When Maxima says that the 927 has a long residence time, they're not kidding, there was a puddle of it in the bottom.
- britincali
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- Joined: May 31st, 2007, 7:10 pm
- Location: Barstow, CA
A good bro of mine came up with this suggestion.
He seems to believe that a lot of the cracking problem in the CR's has to do with that huge intake port. If you've ever seen a Kawasaki cylinder, the main difference is the fact that the Kaw has a couple of bridges on the intake side. Bridges=support. It's not just the 500's that have this problem. He had a CR250 come to him in a box, blowed up, that suffered from the very same thing. Upon further inspection, one thing stood out....it, too, has a very large opening back there. He thinks that a couple of bridges back there would solve this sort of problem. An aluminum sleeve, with bridged intake, plated. The only problem, getting a piston off the shelf. We're talking custom, and that ends up costing a few dollars worth of beer money. I've been kickin around the idea of tryin it for a few now, but my lathe really isn't worth a shit as far as cutting something close enough. But I bet LA Sleeve could do it.
Than it would be a matter of getting a piston made, but that wouldn't be much of a problem in itself, just like I say, cost some $$. Than how would it effect performance would be the next question.
Still more cost effecient to check it every yr, IMO
He seems to believe that a lot of the cracking problem in the CR's has to do with that huge intake port. If you've ever seen a Kawasaki cylinder, the main difference is the fact that the Kaw has a couple of bridges on the intake side. Bridges=support. It's not just the 500's that have this problem. He had a CR250 come to him in a box, blowed up, that suffered from the very same thing. Upon further inspection, one thing stood out....it, too, has a very large opening back there. He thinks that a couple of bridges back there would solve this sort of problem. An aluminum sleeve, with bridged intake, plated. The only problem, getting a piston off the shelf. We're talking custom, and that ends up costing a few dollars worth of beer money. I've been kickin around the idea of tryin it for a few now, but my lathe really isn't worth a shit as far as cutting something close enough. But I bet LA Sleeve could do it.
Than it would be a matter of getting a piston made, but that wouldn't be much of a problem in itself, just like I say, cost some $$. Than how would it effect performance would be the next question.
Still more cost effecient to check it every yr, IMO
Kalkaska, the inbred capital of Michigan. ....a place you can walk into the greeting card aisle and find one that reads "Happy Birthday Uncle Dad"
- britincali
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- iggys-amsoil
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- britincali
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iggys-amsoil wrote:You know, if Glen knows about it, why does Brit have one?
Ive never seen a cracked one personally, I'll bet the cracking is happening on nitrous/alky bikes or a bike that pinged badly.
Coolness list by 90cr500guy
Bob's = 50/50
Cepek = cool
Solidbro = cool
Brit = loser
Stoffer = 1 up from Brit
MFDB = cool
Danny = ok
Bob's = 50/50
Cepek = cool
Solidbro = cool
Brit = loser
Stoffer = 1 up from Brit
MFDB = cool
Danny = ok
- dannygraves
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dannygraves wrote:Brit doesn't have THAT piston, he has the more recent design.iggys-amsoil wrote:You know, if Glen knows about it, why does Brit have one?
Nope the one I have is the old style wiseco, dont forget glen built that motor awhile back.
Coolness list by 90cr500guy
Bob's = 50/50
Cepek = cool
Solidbro = cool
Brit = loser
Stoffer = 1 up from Brit
MFDB = cool
Danny = ok
Bob's = 50/50
Cepek = cool
Solidbro = cool
Brit = loser
Stoffer = 1 up from Brit
MFDB = cool
Danny = ok
- dannygraves
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were talking about 3 generations of wiseco here, I have one like the pic that came out of my bike, lets just call that gen 1, the sides were almost flat like in the pic. The one you have is the next after that, lets call it gen-2 where the sides dip in, but only on the intake side, which is the same as whats in my bike now (not at risk of cracking) then the most recent is the boat anchor without any trimming on the side, lets call that gen-3. Gen-3 is a result of economics, wiseco trying to cut cost without lowering the price for us...they make more money. Gen-2 was developed to make up for craking gen-1 pistons...
Make sense???
Make sense???
'09 kx450f 4-Poke
Gen-4 trail bike --SOLD--
Gen-3 badass trail/mx bike --SOLD--
Gen-1 built dunes bike --SOLD--
'05 klx110 --SOLD--
'95 pw80
Gen-4 trail bike --SOLD--
Gen-3 badass trail/mx bike --SOLD--
Gen-1 built dunes bike --SOLD--
'05 klx110 --SOLD--
'95 pw80
- dannygraves
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