Hi all
i have a 250mk3 and have noticed a strange noise from the engine/gearbox area on a frequent basis,it makes a grating noise that sounds like all hell is about to let loose then i back off and the noise goes.all gears change ok.the clutch is fine and the engine seems to be ok,any ideas before i strip it down?

hi kreid does the noise seem to go away the higher the engine revs it then it could be your exhaust valve clattering ? mine does same & also goes away when you shut off revs.any one else

Couldn't have a guess without more information.

The noise is harsh and violent and it sounds like crunching gears,looks like its going to have to come apart.off to the lakes week in a weeks time so much to do.

kreidlergp wrote:The noise is harsh and violent and it sounds like crunching gears,looks like its going to have to come apart.off to the lakes week in a weeks time so much to do.

Drain the oil and check for metallic deposits.

take the alternator cover off and try wiggling the rotor. sounds like a main gone or even the balancershaft bearing. I would say though that a strip down is on the cards.

[quote="Jonorow"]take the alternator cover off and try wiggling the rotor. sounds like a main gone or even the balancershaft bearing. I would say though that a strip down is on the cards.[/quote]

From the description does not sound like the balance shaft--but i agree it could be, fairly common problem
not sure on a mark 3 but on mk1, you don't need to take engine out
i was told(wrongly) the noise on mine was main bearings when it was actually balanced shaft--someone posted a good picture on here of one which mirrored what mine looked like.

As previously said check the oil for swarf and if not look at the balance shaft before a full strip and possibly save yourself a lot of cash and grief.

no metal particles in the oil but to be on the safe side i will give the engine a full strip and keep you posted.

kreidlergp wrote:no metal particles in the oil but to be on the safe side i will give the engine a full strip and keep you posted.

Have you managed to pin the noise down to any particular engine cycle, eg accelerating , gear change, ect ect .

I agree with what others have said, before stripping the engine down try and establish where the noise is coming from.
The balance shaft can make an awful noise when it is on the way out but is easily missed in a full engine strip down.
Is the noise is there when the bike is in neutral?
Does it rise and fall with engine revs?
Get a screwdriver and place the blunt end to your ear and the pointy end against the engine casing and listen at various points around the engine. Using this method it should be possible to pin point the likely fault.
If it is the balance shaft the noise will be very loud where the gen cover meets the front sprocket.

I have taken the motor apart and first gear is damaged (the small one on the input shaft) i have ordered a gear box off feabay and hope to have the bike ready for a ride over salter fell next friday.

hi kried if you get your bike fixed & there is room for another crm on the ride out let me know thanks chris

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Good news that you have found the problem