how often should you replace the top end on a rm 85?

i got a rm85 that i want to know alittle about... how often to replace the top end, what other maintnence? thanks

you will lose power when it needs work. the best way to tell ahead of time is run a regular compression check. any thing below 80 pounds and it will barely run. you need to check and adjust the chain . change the transmission oil. check the air filter. and all the cables on a very frequent basis. tire pressure is also important.