Hey Guys, need some help from the experts here!

My 2000 F4 has some rattling sound on deacceleration from the eninge.
When you twist the throttle it just runs fine and the moment you release u get a strange vibration and rattle.
Also on cold start there is thak thak sound on startup.
What it could be?

 

Are you able to hear the noise when the bike is in neutral or only in gear while you are riding it? I have to think about it but maybe someone else will be able to help you before I can think of something.

 

not really the sound on neutral and idling is not much but yeah if we revv the engine there is some noise. And you can feel the noise is from the block and not from the gearbox. The sound is not even from the CCT side, we open the stator thinking the nut would be loose and making noise, but it wasnt the stator.
The only thing i can think of is the main bearings. Any idea from where to order and how much would be the cost and what all i will need to order.

 

sounds like a cam chain to me. i had main bearings go out in my 929 and believe me the noise never went away. also really high temps can be an indication of bearings failing. Does the bike see lots of wheelies (i know on earlier hondas this starves the main bearings of oil but not sure about yours). as far as repair thats another costly one have to line bore the crank journals and all that and oversize the main bearings better off just buying a complete used engine and just swapping it out thats why my 929 now has a 954 motor lol

 

Swapping the engine is just impossible! living in India bro , hardly 6-8 F4's in the country! Will open up the rocker cover and start digging in the engine to check whats wrong! F4 has 42K kms on it compared to my F2 which has 28K kms on the odo.

 

You could do a F4i engine if you're mechanically sound.

 

ok another thing you could do before you start taking serious components apart is to drain the oil and remove the oil filter. cut the filter open and strain the oil through a paint filter or thin it with solvent and run it through some fabric like a strainer and collect any suspended sediments in the oil. after you have done this take a magnet to any of the particles, if they are ferrous(magnetic) then you probably have a bearing failing.

 

Hey guys, are the below 2 parts same?

91021-MBW-J21 BEARING (30X41X21) $18.36

91021-MBW-003 BEARING (30X41X21) $30.73

size is same but the price is half for the J21

 

The j21 is for an F4i. I don't know what the difference is, but I'd bet there is otherwise the 003 would have notes that it has replaced by the j21.

 

hey i saw couple of sites where it mentions 003 is superseded by J21.

here are the sites

https://www.motorcyclespareparts.eu/...px?pagesize=20

(91021mbwj21) Brg,needle 30x41x Honda - 91021MBW003 91021-MBW-003