Scratches on piston.

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Sxviperrules99

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Pulled apart my motor yesterday on my sx viper... I am concerned about 2 things... 2 of the 3 pistons were in very good shape and all 3 cylinders are in great condition. The one piston however has 2 scratches on its skirt in line with the transfer ports. They are not deep but there is a small groove that you can feel with your fingernail. Also, there is one small chip... it's tiny and is located on the head. It's probably about the size of a tiny crumb. Can I use this piston? Also, what's a good cleaner that I can use to clean the cylinders?
Thanks,
 
scratches could be the start of a where and tear issue in that jug, especially around the skirt, you might want to get that jug checked. that little spot on the head should be fine. also a very fine hone can clean that jug right up. 3:16x (yammie tony)
 
Sxviperrules99 said:
How do I check my jug??
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There are a couple lines on the jug but they do not feel like anything when I rub my fingernail on them.... the jugs all have good cross hatching. Can I use anything to clean my cylinders? This is my first rebuild so I don't want to use anything that will work it's way into the grooves... I guess I could just put them in hot soapy water and then dry them with a compressor?
 
I would check the specs on the pistons and the cylinders. If everything is in spec I would maybe lightly hone the cylinders and put it back together. Maybe with a new set of rings depending on miles of current rings. If you have the service manual it tells you where to measure the pistons and cylinders. I scrubbed the outside of my jugs with a small stainless steel wire brush in a parts washer and it worked ok.
 
drew24 said:
I would check the specs on the pistons and the cylinders. If everything is in spec I would maybe lightly hone the cylinders and put it back together. Maybe with a new set of rings depending on miles of current rings. If you have the service manual it tells you where to measure the pistons and cylinders. I scrubbed the outside of my jugs with a small stainless steel wire brush in a parts washer and it worked ok.
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Here are some pics... it seems that the scratches are in the line of the pistons ring gap.... could the rings have stretched scratching the cylinder walls and therefore scratching the skirt of the pistons?
 

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Those are pretty good scratches. I have 6 wore out pistons here and none have scratches like that. A couple of them have a few little scratches in that area. How many miles on those pistons and rings? Looks to have some blow by. At the very least I would measure them. They might need replaced anyway.
 
drew24 said:
Those are pretty good scratches. I have 6 wore out pistons here and none have scratches like that. A couple of them have a few little scratches in that area. How many miles on those pistons and rings? Looks to have some blow by. At the very least I would measure them. They might need replaced anyway.
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Only 3000 miles.... the sled was ridden pretty hard by the previous owner though. Do the cylinders look ok to you? You think I should just spend the extra $350 and buy a set of wisecos?
 
I would bet the cylinders would be fine with a hone. They are meant to be rode hard. I am no expert by any means but in my opinion I would get new oem Yamaha pistons and rings. My pistons had 5000 miles on them and were .005 out of spec so I changed them just because I would rather play it safe. From what I have read proper warm up with wisecos is critical so they don't cold seize. It is important anyway. I feel good gas and oil is important also. I am sure one of these guys with a lot more experience can give better advise.
 
I wouldn't run wiseco unless you plan a building a race sled. I would use either OEM or spi pistons. I use spi and everybody I ride with uses spi. But it's your call everyone has their opinion on what piston is the better one. Also depends on how much money you want to spend.
 
yamahamark said:
I wouldn't run wiseco unless you plan a building a race sled. I would use either OEM or spi pistons. I use spi and everybody I ride with uses spi. But it's your call everyone has their opinion on what piston is the better one. Also depends on how much money you want to spend.
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I think I'll order up some spi pistons... I'm confused about the honing... I was told not to mess around with honing a nikasiled cylinder. Am I wrong?
 
get new piston, whatever your choice is, this jug can be lightly honed. it will clean up like new. those are odd looking scratches. 3:16x (yammie tony)
 
looks like not warming up properly, it scored the piston like it was trying to cold seize Did it happen to be the mag piston? Good thing you had oem cast pistons or you might of had bigger problems

i always let my SRX warm up for a good 10 minutes even on cast pistons 15 if its below 0 degress

Tony, he almost 4 point cold seized that motor. look at those marks on the intake side of piston. those aint scratches LOL
 
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tomseal6 said:
looks like not warming up properly, it scored the piston like it was trying to cold seize Did it happen to be the mag piston? Good thing you had oem cast pistons or you might of had bigger problems

i always let my SRX warm up for a good 10 minutes even on cast pistons 15 if its below 0 degress

Tony, he almost 4 point cold seized that motor. look at those marks on the intake side of piston. those aint scratches LOL
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I always let my sled warm up for at least 10 minutes... the marks are on all the pistons but the PTO is the worst. Can I just clean the cylinder up with one of those keenbrite pads instead of a hone? We don't have a local parts store here.
 
Sxviperrules99 said:
I always let my sled warm up for at least 10 minutes... the marks are on all the pistons but the PTO is the worst. Can I just clean the cylinder up with one of those keenbrite pads instead of a hone? We don't have a local parts store here.
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I don't doubt that the previous owner didn't warm up the sled tho... the thing was definitely ridden hard.
 
tom, their not scratches, what are they ? look at that jug, jug is indeed scratched/ scuffed, this very well can be the beginning of cold seizure, but a perfect strait scuff that goes to the top past the ring landing. this jug can be honed with a very lite stone. 3:16x(yammietony)
 
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