Strnge noise in low temps

[Anonymous]

Hy,
Now in Belgium the weather is prtty cold; -4 deg so around 24 F I think.
I have a 1000 G from 1979 with pod filters...
My engine makes a strange noise when accelerating: like air or exhaust leak: pff-pff-pff but not when iddle. I do not think it is exhaust as I do not see anyhting...
What do you think it is, should I worry?
Thanks
olivier

[Anonymous]

Hi Olivier,
My 400 is doing this but it is because an exhaust flange bolt broke off. It only makes this noise under hard acceleration like you said so it will be difficult to find. Your best bet is to retorque your exhaust bolts and set your valve clearances. I've been riding my 400 down to a bit below -12C and this is the only noise that it makes so far. It also makes my exhaust pop from both ends rather than just out the back when I close the throttle so I kind of enjoy it.

Good luck, Steve

[Dink]

The sound you mention is almost definitely an exhaust leak, where the headers enter the exhaust port. Try removing and refitting your exhaust , this should cure it.
Dink

[Anonymous]

I did refit my exhaust but hte noise is still there. less pff pff but still noise from left side. Is it possible that the valves have to be adjusted??? That the noise come from valves???
Olivier

[Anonymous]

Maybe you could get a few friends to take a listen. The more ears the better. The valves actually make a ticking noise but it is worth a try. If you do decide to set them you could retorque your cylinder head just in case the head gasket is the problem. Could it be a broken vacuum hose that is sucking air? It sure sounds like you have something leaking.

Steve

[Anonymous]

Hello,
I inquired a bit more, the noise is jsut above 2500 rpm and only on gear (not on neutral), it definitively does not come from exhaust. Could it be from clutch.
Note that the outside temp is still quite cold...
Olivier

[Anonymous]

Does your model have exhaust flange gaskets? If so they may have flattened or cracked. Check em closely or just replace them since they're probably the originals. You shouldn't have a reoccurrance for another what, 15-20 years??

[Anonymous]

I think the noise is comming from the clutch, is it possible?
It happens more and more especially beetween 2500 and 3500 rpm.
Is it difficult to repair?
thank you