Chain help

[julesh]

Can anyone help me this is driving me insane, KTM 890 duke r, I had a new chain and sprockets 2000 miles ago I went down one on the front and up 1 on the back, since doing this I've had real issues with the chain.
Set at the correct tension, perfectly aligned both chain adjusters exactly the same and a laser put down the chain, it's fine for the first 1/4 of the chain before getting tight as a drum then goes back to fine then tight as a drum 2 or 3 times in 1 complete rotation of the chain, I've bought a new chain and fitted that in case it was a "bad chain" exactly the same with the new one
Thinking it maybe the sprockets I've checked them they are both straight and true, I've even replaced the cush drive rubbers ....what next please ...getting very frustrated with it

[Jug]

One of the sprockets is to blame. It is likely not perfectly round.
Try refitting your old sprockets one at a time to find out which of the new sprockets is the problem.

[TLS-Moose]

Drop the chain off and spin the rear wheel, watching the sprocket teeth. Try and do the same with the gearbox sprocket. Sounds like one of the sprockets is oval ...... pr perhaps not seated/centred correctly.

[ptolemyx]

Might be failed sprocket carrier bearing? Though if the cush drive rubbers are nice and tight and the wheel bearings are fine then that would have minimal effect???

[julesh]

Thank you chaps....

[Ducaki]

JT sprocket ?
If you plan to use it set the chain at its tightness.
Sounds like the rear if it happens about 3 times per chain revolution sprocket chain about 120 links divide by sprocket about 40 teeth = 3

[Ruffian]

Sounds like oval rear sprocket, front as smaller probably wouldnt be as noticeable.