Thumper Club Forum

Technical => Bike Problems/Questions => Topic started by: guest146 on July 09, 2008, 09:04:20 AM

Title: NX650 question
Post by: guest146 on July 09, 2008, 09:04:20 AM
My Dommie like many others has a top end rattle. Everyone tells me its the camshaft on these but I suspected piston slap, but! When topping up or changing the oil for a few moments on starting its silent. My thoughts on this are that oil finds it way back down the breather pipe which exits near the filler into the cambox so making it quiet. So it seems it could be the cam. my question is what is it that makes the rattle as it runs in strong bearings and I don't see any problems with the rocker arms. Been told it will be the decompresser. Does the started version have one?

Your thoughts please

Ken
Title: Re: NX650 question
Post by: Steve H on July 09, 2008, 09:45:38 AM
I beleive the dommie has a auto-decompressor in the camshaft, which could be rattling. Piston slap would tend to go away when warm, as the piston expands taking up the extra clearance. Unless its really slappy, and would then sound awfull when cold.
Title: Re: NX650 question
Post by: guest146 on July 16, 2008, 05:30:48 PM
You have got me thinking now. How does this decompresser work How does it manage to decompress each time you start the engine with no cables. What wears to make them rattle. Does it really need it.

Studdied the picture in the manual but no wiser.

Ken
Title: Re: NX650 question
Post by: Steve H on July 16, 2008, 09:20:18 PM
Quote from: kerabo on July 16, 2008, 05:30:48 PM
You have got me thinking now. How does this decompresser work How does it manage to decompress each time you start the engine with no cables. What wears to make them rattle. Does it really need it.

Studdied the picture in the manual but no wiser.

Ken

At a guess its a centrifugal based device which changes it position as the engine gets up to cranking speed. Other than that no idea.
Title: Re: NX650 question
Post by: mini-thumper on July 25, 2008, 08:17:19 PM
Ken
You may have seen this already:   http://www.xrv.org.uk/forums/showthread.php?t=18546 (http://www.xrv.org.uk/forums/showthread.php?t=18546)

It posses more questions than it actually answers but it offers some interesting theories on Domi engine noises.

Cheers

Boyd
Title: Re: NX650 question
Post by: guest146 on July 25, 2008, 08:35:22 PM
Cheers Boyd

When I get some motovation I shall have the top off and see whats going on. I bet it would be OK without it or. In the book it looks like a one way clutch with rollers.

ken