This is why you don't run a CAST piston

[kaw rider]

This is what happen last night.

[stewart]

this is your kx 500 on cast piston  .....  like the old commercal  this is your brain on drugs ......... very sad

[doordie]

I?ve been there!

Sorry for you.

[kaw rider]

hopefully i will have it ready for next weekend.

[doordie]

some one should report you guys to the moderator for posting such foul pictures.! I feel oozy

Rub it in!

[Polar-Bus]

This is what happen last night.

Not to rub salt on your ugly engine failure, but things happen for a reason. I personally can't blame soley the fact that you were running a cast piston caused a failure vs. a forged piston. Cast pistons are incredible strong PROVIDED the tighter tolerences are maintained. Cast pistons expand less than forged so the tolerences can be as little as .002". Forged psitons expand differently and typically need to set up around .005" (hence the common forged piston "knock" when cold. How are the crank bearings?

[stewart]

old wise japanese man say.......  cast  wont  last

[Albertan]

Other than a bit of extra clearance when the engine is cold, has anyone had any problems with Wiseco forged pistons?  I'm puting a Wiseco into my wife's KDX220, because they have a documented problem with stock pistons which seems to be cured by forged pistons.

[kaw rider]

my problem was operator error.

[quincyman]

Other than a bit of extra clearance when the engine is cold, has anyone had any problems with Wiseco forged pistons?  I'm puting a Wiseco into my wife's KDX220, because they have a documented problem with stock pistons which seems to be cured by forged pistons.

I have talked to Dealers and engine re-builders who swear by the stock Kawi pistons. Both for the KDX220 and the KX500. They claim you can ride the same piston for years with no problem, which they say you cannot do with a Wiseco.

The dealer claims the reason the stock 220 pistons break is the motor is not designed to handle the increase rap speeds by adding after market pipes, taking the airbox lid off and replacing the reeds with power reeds. Once these changes have been made the guarantee has been voided and Kawi will not cover it.  If left stock he says the bike revs slower and the piston slap does not become an issue. Thus the bikes can run for many years if left in stock configuration. He may have a point but who leaves a bike in stock config? I didn't so I changed out my piston immediately on my 220. Other KDX owners suggest if you ride much at all you need to change the Wiseco out yearly.

When my KX500 cylinder was redone this time around they recommended the stock piston for the tighter tolerances. He made the same basic claims as the dealer. It will last longer. So I went ahead and went that route. And no, he does not sell Kawasaki's but he has been doing these cylinder valves on re-plated KX500's for 30 years.

I will be monitoring this closely. Is there any advice on increasing the longevity of a stock piston and far as breaking them in and engine care procedures?

[quincyman]

Regardless of what kind of piston you use you should freshin up your top end once a season or every 40 to 50 hours to avoid piston failures. if you run cast pistons typicaly you find hair line cracks in the skirt if you go to long. Cast pistons work just fine as long as you don't run high compression,don't ever experience detonation or see lots of sustained high rpms and change your pistons regularly. A hour meter is a good idea on any bike to track maintenance intervals. I personaly have never seen a forged wiseco piston with a crack in it. I have been using them for years, I have melted down a few, I have had a ring land break before do to head gasket leak but never any cracks in the skirt

Is that 50 hours of racing or 50 hours of any kind of riding?

I never push the bike to it's limits in the woods. Every now and then in the desert I will push it to the max and even then usually in short bursts cause that's all it takes to get where I am going. To rap it out for more than 10 minutes would be rare indeed.

[Hillclimb#42]

 I rebuild, at least top-end during winter months. alot of guys, like you said(BDI) rebuild more often. I know of some rebuilding three times/season. It really is cheaper to replace piston and rings and not cylinders and cases. Weiseco pistons have been good to me also. Aluminum piston is softer than cylinder, so more wear and damage happen to it instead of cylinder, and I believe has better design in piston skirt. I also ride with some guys who refuse to fix anything till it actually breaks. Riding wore out pistons and bearings cause plenty of problems. Its much easier to tune fresh motors and it won't leave you sitting at the truck, while your buddies are out having the time of their lives.
 My own disaster happened this spring after rebuilding my k5. I bought a basket-case and spent plenty to catch up with neglect on the 500. Took the bike down to frame, powder coated it, replaced everything that might be an issue, but overlooked carb slide. On the first kick, the slide was open about 1/4 " or better and it sounded like it was wide-open. The fresh rings heated up instantly and caused enough fire that I could not kill the bike. It melted down in about 20 seconds. I felt like I was sick for a week. Luckily my motor-guy was sympathetic and put a rush on the re-rebuild! If a pre-teen can kick your bike over, you need some compression guys. Keep the Kaws on top!!!!!

[FuriouSly]

On the first kick, the slide was open about 1/4 " or better and it sounded like it was wide-open. The fresh rings heated up instantly and caused enough fire that I could not kill the bike. It melted down in about 20 seconds.

My own opinion and techniques...  never run a bike on the stand, always start and be ready for the unknown on the ground, sitting on it.  Just some info for anyone in a runaway situation on the stand, get it on the ground and stitting on it...  pull the clutch in, drop it in gear, apply 100% brakes, and dump the clutch...  instant motor kill.  A little crunching to the tranny upon clicking into gear but not as much damage as a nuke job.
Sly

[raredesign]

wow! what a great thread! lots of information.

someone on here mentioned aluminum pistons.. was that wiseco you were talking about?
Secondly, what piston is softer? ...cause that is what I want. I would rather wear out a piston than wear out a head and have to replate.
I plan on rebuilding it soon, so I would like to know which way to go.
I have been told that wiseco is harder so stay with stock pistons and you can replace 20 stock pistons for every head.

What are your thoughts?

[Hillclimb#42]

On the first kick, the slide was open about 1/4 " or better and it sounded like it was wide-open. The fresh rings heated up instantly and caused enough fire that I could not kill the bike. It melted down in about 20 seconds.

My own opinion and techniques...  never run a bike on the stand, always start and be ready for the unknown on the ground, sitting on it.  Just some info for anyone in a runaway situation on the stand, get it on the ground and stitting on it...  pull the clutch in, drop it in gear, apply 100% brakes, and dump the clutch...  instant motor kill.  A little crunching to the tranny upon clicking into gear but not as much damage as a nuke job.
Sly

Good planning, of course too late now. Actually crossed my mind, but before I could push it away from the vehicles in the driveway, it gave up. Needless to say, I was more prepared the next time and will be from now on.
 Yep wiseco. Way better than stock. I am a believer in after market parts. Pipes, silencers, reeds .....all of it. Pull the old stock piston, when you get the wiseco and set them next to each other, you'll see. Its that obvious.