I have a piston issue. I want some opinions.

jthemmer

jthemmer

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Joined
Jul 24, 2012
Messages
118
Age
35
Location
Central Iowa
In the process of triple pipes so I took the cylinders off and found one piston to be scratched. The cylinder looks good just light markings no scratches that I can tell. I think I will have it honed. Should I just replace this one piston or do all three?


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that dose not appear to be cold siezure where its located, look more like lack of lubrication. your jetting looks good. i would go through that carb, also time for rings, alot of blow bye. 3:16 (yammie tony)
 
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what is blow by? I had a holtzmann vari flow on for a long time and finally took it off this year. I wonder if that had something to do with the piston. I never thought it worked quite right.
 
Blow by is caused by combustion leaking by the rings because they have lost some of their tension causing a carbon buildup,that would be the dark deposits on the sides of the pistons.
The Holtzman could very well have been the cause of the marks on your piston.I had a Holtzman tempa flow for a few years on my SRX and because of the finicky nature of them and their tendency to run lean after a short stop and go I experienced a couple of lean burndowns.If you took yours off I'd do what the other guys have recommended by changing that piston and 3 new sets of rings.While you have it apart just to be on the safe side raise the needle jets in the carbs by lowering the e clip by one notch to allow a richer mid-range,which from what I've read tends to be an area of concern for Vipers as they tend to run lean in mid throttle.
 
Yeah I bought the sled with 4k on it and it had the vari flow on all its life. Shortly after buying it I adjusted the needles. Now I have the carbs ready for slp's specs. The sled now has 5200 miles and will get all new rings and I purchased a new oem piston.
 
if that scoring is limited to the intake side of the piston only, figure out where its sucking snow or moisture from.

if there was a problem with the holtzman, all pistons would be similar. that piston shows signs of sucking water and/or snow.
 
Yeah it's getting water and washing the oil film off the piston causing scuffing, look for holes in the pre filter
 
Okay. It would have to be air box related right? If it was a torn carb boot or something I would have known for high idle.
 
do you have any pre filter material in the hood scoops or on the air box lid?

brothers 02 viper did inhale some snow when powder riding until he put an outerwear's pre filter kit on it. after that there was no problem with snow injestion.


you can see them in this pic from jan 09 when the crank let go on the ty ride.
 
most common problem is the airbox to carb boots not being properly installed. could have been that the boot wasnt completely around the carb or not secured to the airbox.

unless that sled sees lots of over the hood snow or the top of the airbox isnt properly snapped on, normally the snow isnt ingested through the airbox, but dont rule that out as a possibility. snow dust can find its way through most anything.
 
My guess. It was overheated a couple of times. And I'm not talking about boiling all the water out of the motor. If you run a good long pull you can hurt the engine then off the throttle and and you wont even know you did damage. Do that several times. Then the piston finally gives up and the rings stop sealing. Usually the leading edge of the piston starts to roll over and the ring land jams the ring. I have had a bunch of pistons look that and it was heat failure with jammed rings most of the time. Personally I would either run it to lean with jetting. Other times shitty gas. Another time head was to tight. Keep in mind this motor is 13.5 to 1.

Has this engine had the comp reduced head mod? You will need it with ethanol gas?
Do you run ethanol fuel?
Don't run compensating devise of any kind.
Get a temp gauge inline tee to monitor the coolant temp.
Check that single carb for plugged pilot. That will do every time

---Mac---
 
I run premium with octane booster and clean carbs good every year. No head mod. I like the idea of the t gauge I could make one at work. I think this was something from previous owner. When I bought it my power valves were stuck in there from never being cleaned so it probably got neglected a bit. The sled ran fine before I started tearing it down, at least I felt that it did. Oh and it never had the needles adjusted either and I shortly after buying it added the rear cooler. So I think you are right that it probably got hot a few times.
 
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Let me ask. That top ring does it float perfectly. The pic makes it look jammed flush with the piston. Also remove the piston and look underneath. Is it burned blue and look like ash? Please show pic for others to see.
 
Both rings were free. The top one was hanging loosely below and that is why it seemed snug where the pic showed it. they should be loose correct and not lodged in there?
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