noise coming from motor

[CSR400EX]

i was riding my 450 yesterday, making some practice holeshots and on the way back it started sounding like something came loose and was floating around in my motor. it still ran good tho. upon taking it apart, i havent found anything wrong except the cam chain is binding up and has kinks in it. could this be what i am hearing??

[blacknblue#2]

could possibly be.. a stretched timing chain can sound horrible. But its odd that it just happened at once. What all have you taken apart. I would take everything apart down to the main bottom end cases. I wouldnt split them unless you have to but all the top end and both outer cases i would take off to be sure.

[CSR400EX]

thats how it sits as of now, everything except splitting the cases. the crank feels good and smooth. its funny cause it made that noise, then quit doing it for a minute then did it again, and so on. its not a constant noise.

[blacknblue#2]

That does seem odd. As you put it back together i would check everything to be in tolerance. mine done something sort of this effect once before and i found out that the decompressor was loose and flopping around. in return meaning when the exhaust valves got to really cranking then the decompressor couldnt keep up and when flopping like a limp d*** lol. if that makes since to you.

[Sjorge450R]

was it a slapping sound, clanking, or what? Did you inspect the valves and all of their components?

[CSR400EX]

yea, im just gonna put it back together with a new timing chain and just check everything as i put it together. its more of a clanking noise

[859davidt]

I would pull the flywheel and check behind it. There is a metal guide under the crank gear that the chain rides just above it. Held on with and 8mm head bolt. I have seen the chain get sloppy and bend these out of whack and make a terrible noise from time to time. Also, check the front cam chain guide to make sure the j-hook at the bottom didn't get broke off. Sometimes a slapping chain will break these and the part gets tossed around in there creating a ruckess from time to time. Hope this helps.

[CSR400EX]

ok i will look for that as well. im hoping to get it back together to make a few races this year, i finally get a MX bike and it has to take a poop on me :rolleyes:

[OnTheGas69]

How many hours are on the engine? You might want to get a factory honda shop manual, fly wheel puller, clutch holder and gasket kit and go ahead and just split the cases just to make sure. It's not too hard once you do it a few times. Just make sure your shift forks are aligned in the drum properly when putting it back together. lol. Did you check your clearances when you pulled it apart? In,EX, and decomp? That kinked cam chain wasn't making her happy for sure. Good luck man,

859davidt - Good point man, that seems to happen more than you would think

[CSR400EX]

well, im not sure on the hours on the motor, but i rebuilt this motor for a friend about 11 months ago. put new honda crank, rings and valve springs in it. i have had many 450r motors split before, just trying to find out if it could be something dumb lol. i will re-check the clearances on the valves in a few.

[OnTheGas69]

Nice, that's cool. Hopefully it was just the cam chain. Good luck man,

[CSR400EX]

well i re-checked the valves, and the intakes and exhaust are good, but i had .020 on the decompressor. this is with a feeler gauge under the rocker arm for the exhaust and measuring the decompressor at the same time. from my understanding it should be .011? am i correct?

[CSR400EX]

bump, anyone??

[OnTheGas69]

The decompressor clearance is:

Right side exhaust valve clearance + 0.15mm + or - 0.02mm
(0.006" + or - 0.001")

So if your exhaust clearance is .28mm, your decompressor clearance should be .43mm

[CSR400EX]

well, i put in just a timing chain and adjusted the decompressor to spec and so far, so good. i will find out how good it holds up at the monster truck show this weekend. and thanks again for the help!