i just bought a 2002 honda foreman es 450 4x4. When i rev it pretty high before i shift the tranny seems to lock up or something and i can't shift up or down. i have to turn the engine off and then on again for it to shift. Whats the problem, could it be a fuse, or is it that angle sensor thing.

 

I also have a 450 foreman ES purchased last August (new). For your problem either take it to the dealership and pay $60 pr/hr for labor or buy yourself a service manual. My manual cost $100CDN. It describes how to troubleshoot the fault that you describe (by holding both the up/down shift buttons and turning on the key trouble codes will come up; you need the manual to know what these mean). With some mechanical know how you can fix most of your own problems (as well as ensuring you do the routine maintenance correctly). If you have riding friends with the same kind of quad the $100 is pretty cheap (you may not be able to fix everything but why give the dealers all your money). This doesn't answer your question but I hope it helps!

 

Check the easy stuff first... how long since the oil has been changed? Correct level and viscosity?
The battery needs to be about 12.4 volts or higher.
How cold is it, outside air temp, when it happens. Does it shift better once its warmed up?
Has the gear position indicator blinked, when turning it back on? How many times?

 

it wasn't that cold outside and all of the fluid levels are good. It happens whenever i give it more than half throttle.

 

Even when its all warmed up? Do you back off the throttle when you press the upshift?

 

Most likely the angle sensor, or the speed sensor, or poor connection. Yes, check battery cables to make sure they're tight as well as all the locking couplers you find, check your fuses. Also, check your clutch adjustment. The 02 has a diagnostic memory, and has probably left codes there that can help point you in the right direction. It's not hard, but you really kind of need a manual to refer to. Don't forget to erase the memory after you get it fixed.