i have a 87 cbr 1000 and its showing 27000. mi

the bike is in great shape so i would say its the true miles
i noticed that it has a slight rattel when its sitting at an idel but once it gets up around 2000rpm it goes away

does it need a tensioner already ?
or what can i do to fix it

 

A slight rattle at low revs is common on these. It can be quite loud on start up but should lessen heaps once warm.

If the miles are true it should be fine.

 

It will help if you sync the carbs
Keep the idle at 1250 RPM or a bit more, which is where they are happiest.
27000 is about right for a cam chain renewal - I did my first about then, but you can happily ride the bike with some noise for ages without any damage It's just irritating.
The tensioner has been revised by the factory and the revised one has a longer plunger - will fit your bike and all other marks. If you need a camchain let me know, I get DID's here which have a masterlink so you don't have to split the engine.
Good luck with it.

 

I've said it before and I'll say it again !!!! She's a Honda mate ! Just get on and ride the bit&h !!!!!!!...She'll be right !!!!

 

It's important to use motorcycle oil. Because the oil is shared with the transmission, it gets crushed by the gears. MC oil is designed to take the pressure of the gears. Shell Rotella-T is what I and other members use. It can take the crushing. Regular car oil can't take the pressures and brake down in a few hundred miles and thin out. It may look good but it has lost its thickness (Weight) and can cause the chain to rattle some.

What oil are you using?

 

My 91 has 41,000 miles and rattles. I use gtx mc oil, and some Lucas. Its better now with the oil change, better as I go faster, so I do. Its doesnt skip, miss or show sign of effecting timing. I chose to leave it alone, and ride respectfully of the old girl. I'm sure she will treat me right.
Bud

 

all of the abbove, and remember the latest version of the camchain tensionner works better with a god viscoity of oil, I changed the tensionner for the revised one and use full synthetic motorcycle oil 20w50 and only a small ratle at start for 10 secs.before I changed the tnesionner and used the 10w40 it was rattling, now purs like a kitten and the motorcycle is 1475000.