i have a 89 cbr 600 with 42,000 miles on it. when i start it up it rattles,sounds like valves when it warms up it goes away. and when you shut it off after warm and then re start it really rattles but goes away quick. the bike has done this every since i got it this last summer and i put 5,000 miles on it. should i ajust the valves or just let it go. and how long do these cbr engines last 4?

 

the noise is the cam chain tensioner, CCT. mines is noisy like that at startup, rev it, or once warm, it goes away. i replaced mine with a new oem CCT, and the noise stopped completely for about a month, then came back. there is a company that makes a manual adjust CCT. do a search, this is a common problem for all CBRs it seems.
i would recomend adjusting the valves anyways if you dont know the last time they were checked.
hard to say how long these engines last, 22 years so far for mine.
Who has the highest mileage Hurricane?

 

michigan_313 has 90,000+ on it. take care of it, it will last.

here is the manual cct...

http://cbrzone.com/sprockets.html

 

yup. CCT. APE makes a manual one, it fits the Cane/F2 I think. you'll want that one for yours. I need to see if they make one for my ninja now.

Tripicana is right, check your valve clearances at least and ensure they're within spec. this bike likes the intakes at .006 and the exhausts at .008"