20 Most Recent 2002 Yamaha YZF 600 R thunder cat Questions & Answers

Yes a 100% teardown is needed. There are two bolts on the case that are under the jugs (cylinders) that prevent the case from being separated. This is a full teardown, you will need to be very good at it or need a friend who is.

This bike and many of the 600 class lose 2nd gear and slip out on hard acceleration, then at easy acceleration as it wears more and eventually the kicking out of gear can bend a shift fork, the parts are not extremely expensive but the labor is going to be high because of a complete removal and teardown.

Im not to sure on street bikes but i know on dirt bikes you pop the seat off first and if needed the side covers too.... then u can access the fuel tank bolt to take it off the frame...

Most likely you have one or more bent shift forks which unfortunately takes a full tear-down to repair and is not a job for an everyday DIY mechanic because you basically have to disassemble the entire bike. plastics, engine out, disassemble engine etc. I don't make youtube videos but I watched this one and the guy is pretty thorough........https://youtu.be/1Tdo8rFeBgg

To remove the seat use the key in the helmet lock. One direction, I think counter clockwise releases the helmet lock, pushing down on the back of the seat and turning clockwise releases the seat. The key hole is located by the left rear foot peg.

Jets might be clogged up or trash in carbs. Remove carbs and service them, then sync them again. This is common on any carborated bike that sits for an amount of time (like during winter), ethanol in modern fuel is also known to clog up carburetors.

Beings as tachs today are electrical instead of the old cable driven mechanical tachs, from your description I'd start with it sounds like an electrical glitch. As if the trigger wire from the coil to the tach is shorting out, or even broken internally inside the outer insulation coating.

On my 03 cat the rear has 47an the front has 14

They are between the carbs on the butterfly linkages.