Rattle at specific rpm under load

[pac]

Hi, I have a mk2, she runs great no engine noise until I'm accelerating and I got this annoying bloody rattle at around 4-5000 rpm (I'm guessing here as have no rev counter). Any one experienced similar problem. ?

[69chris]

my mk2 used to do that, it was (i think) the powervalve 'chattering' as it started to open,
i say think as it sounded like it was coming from up high on the front of the engine and it certainly wasnt the piston/barrel etc as i had it apart to check and all was well,
i just ignored it and it didnt get any worse or cause any problems

[fishtail]

could be chain/ sprockets? you have chain guides and sliders?

[knackeredMk1]

I've had 4 different barrels on my Mk1 and they all sound different, particularly with rattles at specific rpm. All had just had rebores and new pistons.

Like 69Chris I think it's down to fluttering of the powervalve and nothing to be worried about.

[pac]

thanks everyone..I disconnected powervalve cables and 'jammed powervalve' so it could not move..then took bike out....exactly same rattle still there...so I feel confident it's not that..cheers for all advise

[knackeredMk1]

May I suggest that your 'jamming' the powervalve still allowed the movement of the valve on its shaft and the movement of the shaft inside the barrel. This is what I mean by 'fluttering', not the movement induced by the cables.

[pac]

OK, understood...thinking cap back on ! thanks

[fallenmikethebike]

OK, understood...thinking cap back on ! thanks

And here's the fix,
http://www.amazon.co.uk/Pairs-Howard-Le ... 090&sr=8-1

Seriously, tracing noise/rattles is legendarily difficult.
Check all bolts are tight, can you make some washers out of shim for the lever pivot points.
Mike

[knackeredMk1]

A bit off topic - Have you found how many 'new' rattles appear when you take your helmet off while the engine is still running .

[pac]

Not taken my helmet of yet ! OK Mike, the link (to the ear plugs) was really appreciated..even made my Mrs Chuckle and she has as much interest in m'bikes as I have in girl guiding ! cheers from Paul

[back off road]

pac whats wrong with girl guiding i had a very big interest in them when i was about 14 years old

[fallenmikethebike]

^^^^^ you keep your ging ganging and goolying to your self, thanks .
Mike