a funny rattle

At about 4000 rpm my bike has a funny sounding rattle. It did not start until I chaned the oil. It sounds like possible chain rattle in the top part of the motor. Any idea's???

 

have you tried adjusting the cam chain tension? What model is it? earlier models are manual adjusted later have automatic tensioners but some 'coaxing' of the adjustment can be done.

 

What kind of gas are you using? Mine buzzes at 4500-5000 rpm, but it was worse before I started running mid-grade (89 octane).
Also I've been told this may be a carb balance/sync issue. I suspect that I may need to replace my intake boots which are old and beginning to crack, which could contribute to the carb issue. Full tune on my list for next spring.

 

Check the collars on the exhaust downpipes. A loose one can sound like the engine is disassembling itself.

My XJ650 has a harmonic at about 5K rpm. More like a buzz than a rattle though, can feel it as much as hear it (although I wear pretty good hearing protection).

 

I'll second that. It happened to me, and I thought I was eating my crankshaft bearings alive.

 

I will check my exhaust collar. It only does it when you are actually riding the bike. You can rev it up and hold it at that RPM and you don't hear it. It sounds like the motor is going to fall apart.

 

It is a 1983 xj 750 I believe it is an automatic tensioner. I was going to take it out and replace it. If any other idea's please help. The exhaust collars all seem to be tight. It started making this noise after a recent oil change.

 

What kind of oil did you put in?

 

I put in 10w 40w cheap oil I am going to change it to 20w 50w I think and also run premium gasoline, and see if that will help.

 

Auto oil is slicker, right? If that was used, could that maybe be a clutch slipping a bit?

 

Again, it depends on the oil. If it says "energy conserving" on it somewhere, avoid it.

 

yes i did use auto oil and my clutch is slipping a bit I put motorcycle oil in it right away and see what happens thanks

 

You might have to run it a bit and drain/refill it again to flush out the friction modifiers. Castrol 4T 20w50 is available at most parts stores and is cheaper than Yamalube.

 

Thank You I will try that this up coming week and see what happens. Thanks again.