20 Most Recent 2002 Honda CRF 450 R Questions & Answers

maybe get a new spark plug.make sure your grounded(earthed). did you take the plug out and check for spark against the motor while you cranked the bike over?

Classic valve train issues. Sounds like the valves are tight. One thing that concerns me is the "sudden onset". Valves usually tighten over time.
Make sure you also tighten the cam chain as well.

Bent water pump shaft or water seal has been damage putting it in

Get the handbook for the bike, besides the clutch, you have to keep the chain and brakes properly adjusted.

The bike has some bent shift forks. The repair is pretty major and requires some special tools. I include a generic diagram to show how the shift forks move left and right to move a slider gear into different gears. Please rate my answer. Thanks!

Maybe a connector problem? Use an ohmn meter to check all the connectors/wires...try to disconnect kill switch as well to test for that malfuntion.

could be timing.

recheck timing
recheck valve clearances
check for inlet and exhaust manifold leaks

There is a breather tube between the carb and head. Remove it and there should be a green gasket and a red rubber o ring. Neither should be ripped or torn. If so replace them and reassemble

Go easy on twisting the throttle. Every time you twist, a shot of raw gas goes into the carb. The bike will flood easily. Put in a new spark plug, clean the air filter and drain the carb float bowl. Then get a can of starting spray. Spray into the air filter and then try to start it. The gas valve is turned on isn't it? Please rate my answer. Thanks.

Always fill your radiator to the top. and make sure the overflow bottle is full to the high mark( if your model has an overflow bottle). Run the motor and after it cools down top it up again. The reason you do it this way is to make sure there are no air pockets in the head. Gas expansion there will push your anti freeze out of the motor and may damage the head.
It can be said for all motor cycle water pumps that if the engine gets hot it is easier for the anti freeze to leak past the water pump seal before it leaves past the radiator cap to the over flow. It is the steady/constant drip that needs to be addressed. I assume you replaced the impeller shaft as well as the seal. It is possible the seal was damaged during the install or one of the sealing cover o-rings or gaskets is leaking on the cover. If you can not ride safely with the amount of anti freeze loss, you should take the water pump apart, inspect, and consider replacing the seal and gaskets again. If the impeller shaft was not changed consider changing that to if there is any noticeable wear at all on the pump seal contact surface.
Use only non-silica formula anti freeze mixed 50/50 with distilled water. Gm Dexcool or any motorcycle anti freeze should be non silica. Silica content is stated on the anti freeze bottle. Silica scrubbing particles in the anti freeze will damage water pump seals in most Honda's.

Until it's full. About a quart. Make sure to use a mix that tests good to about minus 35 degrees F. A premix is a good idea also. If you mix you own, use distilled water only!!

Try putting less coolant in the radiator.