I have had my 300ex for a month. It's a 97, I have no ides how the guy before me took care of it. I was riding and it started loosing power, and knocking real bad, to me it sounds like a loose cam chain and it is too loose so it sliped, and is putting it out of time, and that's where my power loss is coming from.

First thing I did when I got it is changed the oil, so I think it's getting pleanty of oil. The noise got real bad, I stoped riding it, Then I noticed that the plug was hand tight, I got it tight, and decided to try it again, "Worth a shot" it wouldn't start, and was hard to turn over. I pulled the top-end, and found the cam chain real loose, it had atleast 1/2" play, is that normal? Now that I'm into the motor I coldn't stand the frame looking like it was scratched, chipped. I sent it to be power coated Black. All because my enging problem it forced me to do everything.

 

Was it actually a "knock" or a "slap"??

Did you check the timing before you tore it down??

You said you changed the oil right before this happened. What does your camshaft look like? Did you install the oil filter in the right direction? If you didn't..you most likely have burnt rockers and/or the rocker shafts..OR....and/or camshaft.

 

It was more like a slap noise. I made a mistake by not checking the Timing, Compression, before I toar into it. Everything looks great, camshaft is good, the whole engine is clean. Could it possibly have been the cam chain being loose "1/2in play" and might have slipped, so it was way off time. Also the noise was only at idle, when you give it some RPM the noise went away, and the slapping/knocking didn't seem as bad after 5 min of running time.

 

Make sure you ck your chain tensioner before you put it back together!!!