has anyone experienced cold seizing the forged pistons that come with fix kit? had a guy tell me these pistons are nicknamed seizco. would removing the t-stat help prevent it? any input would be appreciated, trying to ease my mind.
wiseco pistons
- Thread starter hj78
- Start date
I wouldn't remove the t stat but maybe installing the by pass kit would be a better option and ease that mind......
http://www.startinglineproducts.com/catalog.cfm?pageID=detail&catalogID=3&catID=18&productID=1518
http://www.startinglineproducts.com/catalog.cfm?pageID=detail&catalogID=3&catID=18&productID=1518
I have no doubt that the Wiseco forged pistons are a better piston than stock. There are quite a few standard Wiseco replacements and fix kits running around out there now with zero issues that I am aware of. I have over 700 miles on mine.
The same materials that companies add to their cast pistons to minimize heat expansion are also being utilized in the forging process. They even share the same low friction coatings.
Cold seizing a motor can usually be blamed more on operator malfunction than on a piston. Any motor deserves a proper warm up before you grab a fist full of throttle.
The cold shot that seems to be getting so much publicity these days is nothing new either. Anytime you stop your motor you stop the coolant flow. You will find the heat will actually increase in the motor. This is why the fan on your car often turns on after you have turned off the car. Again, just give it a couple seconds to get the juices flowing before hammering on it.
Hope that helps ease your mind a bit.
The same materials that companies add to their cast pistons to minimize heat expansion are also being utilized in the forging process. They even share the same low friction coatings.
Cold seizing a motor can usually be blamed more on operator malfunction than on a piston. Any motor deserves a proper warm up before you grab a fist full of throttle.
The cold shot that seems to be getting so much publicity these days is nothing new either. Anytime you stop your motor you stop the coolant flow. You will find the heat will actually increase in the motor. This is why the fan on your car often turns on after you have turned off the car. Again, just give it a couple seconds to get the juices flowing before hammering on it.
Hope that helps ease your mind a bit.
P
pura vida
Well-known member
what he ^ says. cold seizing is a non issue as long as you properly warm up your sled before you ride and after you re-start it. my simple rule of thumb, although not perfect, is after sitting or any amount of time when i re-start the sled i wait until the coolant temp stops dropping and is at least 90 degrees.
pv
pv
Thanks for the input guys. Talked to the mechanic installing the kit and he basically had the same thoughts. Wiseco had problems in 70's & 80's but have made big improvements. He said proper warm up and good to go.
That comment is typical "old school", back when most sleds didn't have thermostats and mechanics thought they were "doing you a favor" by setting you up with a nice, tight fit on your new forged pistons. Fire up your cold sled, dust your buddies with snow and 50 yards later, the motor locks up... It was always those "junk Wiseco pistons", never the monkey on the throttle or the mechanic who set up forged pistons with clearance at the bottom end of the range for cast pistons. We all (hopefully) know better today. Proper clearance, good warmup and you'll never have the problem.
T
theshadowrider
Well-known member
FYI.. A cast piston is usually 4032 alloy which they add silicon to aid in the casting process. This does a couple of things which one is the thermal expansion coefficient is less. Another one, being negative, is the piston is weaker.
Forged pistons are usually 2618 alloy. Their thermal expansion coefficient is greater than 4032, but not by much. Its only 15% more. So to put that in perspective if you have the conditions to have a cast piston grow with heating of .004" as forged piston will grow .0046". So the difference is .0006" on a 85mm piston. Not much more. A forged piston is stronger, holds up to det better, and less likely to break skirts off.
Forged pistons are usually 2618 alloy. Their thermal expansion coefficient is greater than 4032, but not by much. Its only 15% more. So to put that in perspective if you have the conditions to have a cast piston grow with heating of .004" as forged piston will grow .0046". So the difference is .0006" on a 85mm piston. Not much more. A forged piston is stronger, holds up to det better, and less likely to break skirts off.
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Back in 2000 or so, we installed a Wiseco piston in my son's Suzuki RM 125. Within a couple of rides, we had a failure. Upon teardown and inspection, we found that the piston ring locating pin had bored a small hole in the piston, turned itself sideways, and allowed the ring to spin in the groove, and then the ring caught a transfer port, destroying the rest of the piston and the nikasil. Fortunately, Wiseco supplied a new piston and paid for repairs to the cylinder, but that was also the last Wiseco piston I have ever used. Take it for what its worth. Just my .02 I'm sure they make a quality product and many people have had good luck with them.
Shadowrider hit the nail on the head. Basicly people think they can just put a forged piston in a bore fitted for a cast piston. Cast pistons expand way less than a forged piston, weisco makes a quality product, I believe they make one of the better pistons around.
I ran Wisecos in my 995 for 8 years and never seized or scarred a piston. I ran no thermostat and 90 degrees on LONG LONG pulls. Warmup\ and lots of good oil.
I do agree with the comments that the "extra" expansion with a forged piston doesn't seem like much, but think of it this way: Properly fit pistons run basically "right at" the point of contact with the cylinder wall when fully up to operating temperature, with the piston and cylinder wall separated only by the oil film. Relative to the thickness of the oil film, that seemingly tiny .0006" or so difference in expansion is HUGE, so if a forged piston and cast piston are set up with the same clearance, either the cast piston will be too loose or the forged piston will contact the cylinder wall when fully up to operating temperature. While I can't speak to the 700 specifically, in the past, I've typically set up Wiseco pistons of similar bore size with .001"-.0015" greater clearance than Wiseco specifies for my sea-level applications. I don't know if this is still appropriate, but hopefully, someone with specific knowledge can chime in.
What do you do if the clearances are to great or to tight?
You have an issue and you need to send your cylinder to get repaired.
If your cylinders have clearance that is too tight, it may be ok to hone them (special equipment required) to gain perhaps .001" or slightly more if they haven't been honed before. This scenario is very unlikely with factory pistons, but you might see this with an aftermarket piston. If your cylinders have too much clearance, your only option is to have them re-plated and sized for your pistons.
