Im always alittle nervous before the new season and like to make sure everything is running tip top so i dont have problems in the mountains. My question is when should a person replace rings and pistons. Sled is an 08 700 rmk 2470 mountain miles. Compressin is about 115 both cylinders not a 100% as compression tester wont hold the pressure, but with two guys one pulling and the other watching this is what we saw. Question is what is the compression that is still ok to run whats good whats low. And also if comp is good is it still a good prevenitive maint to replace rings and pistons or am i ok to run them one more season. And what is the most common reasons for failure. THANKS
curiosity ring and piston Qs
- Thread starter sevenhundo
- Start date
with 2500 miles...I would repiston it..most likely it would make another season..but if it doesnt, it will most likely take out at least a cylinder, and possibly a crank and cases as well..as for good compression? well every tester reads different, and even humidity can change readings slightly..a good rule of thumb is anything over a 15% drop from fresh is time to repair...rering it(I would do pistons as well) , run it for a bit then run a compression test so you know what it is for future testing..and one thing you are trying to prevent is a piston skirt breaking off..hence changing pistons and rings....
Whats a good piston to go with ive heard good and negative about all. And the skirt breaking off what is that from the piston rocking??? And what does a person do with the actual cylinder walls if there is a lip which im assuming there would be but maybe not. I know to hone them and there willl be a lot more Qs when i go through with it.
brand is pretty tough..weisco's are known for seizing in the old days..but now days seem ok, spi's are supposed to be good, stock are good but hard to get proper clearence on them..as for a lip..not normally on a nicasil cylinder..and as far as honing...it takes a special hone for nicasil and go easy..dont want to remove any material, just rough it up for ring sealing....and yep, excessive bore clearence allows rocking which fatigues piston skirts....
who has replaced the pistons in the 08 700 and what pistons did you use and the results
2,500 mountain miles are high motor load miles, definately time for a new top end, fuel filter, etc. I've put em back together with the stockers and they are still doing well...6's ad 7's both.
I'd have no problem running the Polaris pistons. As long as clearances are set to spec, the Elko pistons will hold up fine.
It doesn't matter how great or poor of quality a piston is, if the clearances are not in spec, then expect issues.
I'd have no problem running the Polaris pistons. As long as clearances are set to spec, the Elko pistons will hold up fine.
It doesn't matter how great or poor of quality a piston is, if the clearances are not in spec, then expect issues.
What clearances are you checking. Im sorry to sound like such a dummy but this would be the first top end on a sled ive done. And why would the clearances be off?? And yes i do have some mechanical knowledge its one of those things that ive never done so i want it done right the first time not just thrown together and make it worse than it is and by the way i typed in the milage wrong its 2740 and what about the crank bearings do they hold up for a while. Thanks for the input and some peace of mind!!!
come on now some other people have ideas. All the info has been greatbut im looking for more details. Everyone says special hone is required i have the not sure what they are called but the regular cylinder hone with the three flat bars and also the one with all the balls. is there more im missing on this. More details the better. Thanks
they make a special hone material just for doing nicasil cylinders, http://www.enginehones.com/niapho.html, when you do the topend you want to measure piston to bore clearence and determine that is and will be within spec after reassembly as well as piston ring end clearence, all are to make the motor perform at its best and live a long life..the polaris shop manual will give you all stock clearences and detailed disassembly/reassemble instructions, most aftermarket piston kits will include paperwork listing desired clearences for that piston setup...
so what pistons would you recomend? You can pm me if that helps any. I think its your fault im doing the top end but appreciate the info.
Maybe im just a little stressed about this whole situation. Im trying to replace my track ive got a pretty much whole house remodel going on. Am i over stressing the specs and all the other stuff with the pistons or is it something to stress about. The specs got me wondering.
LOL...I didnt put 2500 miles on it....lol..just do stock pistons, run a hone thru it (real light just enough to deglaze it), and set everything to factory spec..the 700 is a good motor ...
