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Piston sticking

2219 Views 9 Replies 8 Participants Last post by  stinger
Keep sticking pistons on 600 ves i'ts a four corner stick no burned edges.sled has rugland twins and rugland heads and tempa flow.running two sizes bigger mains than what is recommended. put on 30 miles on and of gas never holding it open for more than a few seconds. seems to happen when going 60-70 then open it up for short distance(100 on speedo) when slowing down not completely letting of gas. motor will shut off sticking piston. but not every time and not always same piston.running 93 octane with octane boast and in regular fuel setting. any ideals please getting real $$$$$$. bleed coolant good also not running hot on temp gauge needle in middle of gauge. egt's never go over 1270's probes are 7 inches from piston skirt.
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Have you had pistons changed? If  so was it bored properly for the expansion? Different pistons have different amounts of expansion.
using stock polaris pistons when had plating done they needed pistons for size. but this happened with stock. only thing changed pipes and heads so if anybody has info or run these pipes and heads before let me know so i know it's something i'm doing or are pipes and heads doing this.
Friend has a 99 rmk700 with twin slps,slp head,boost bottle, V-force reeds anyways he blew it up twice and put the stock single pipe back on and had no problems since.
Sounds like your to lean at partial throttle. You need to do some testing and read your plugs and piston wash at 1/8,1/4 and 1/2 throttle. What type of guages are you using?
What is the oil pump set at,this sounds like a lubrication problem.the oil pump setting should be checked with the carbs installed on the sled and after all idle and cable play adjustments are done.Polaris did have some faulty oilpumps in 2000 so this could be your problem.
at the risk of sounding stupid i'll throw in my 2 cents.
almost sound like what the other guy was saying,lean mid range.main jet size does nothing untill higher range.
does your oil level go down in resevoir.
one last thing,are you warming up good?cold seizing can happen all to often if you dont let it warm up,piston expands faster than jug.
It sounds like it's to lean, what doo the piston top's look like?
Have you ever done a compression test? maybe with that head. you have to high of a comp for pump gas. 1270 is getting up there!
Put the stock heads back on! Sounds like the compression ratio is too high. Probably not burning it down at full throttle because the amount of fuel with upsized main jets is keeping it cool. Autoignition may be happening at midrange because the pressure is driving the temperature up with not enough fuel to keep the piston cool.
If the scuff marks are equally spaced on the intake and exhaust side of the piston, this sounds like a four corner seizure. The explantion  I was given for this is that the piston is expanding faster than the cylinder, reducing clearance between the cylinder and piston. Reasons Given to me; Forced warmup period, or bad thermostat.
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