Possible seizure?

RichHubb wrote: Hello Nessisn,

Yes the bike is modified, it has no air box with cone filters and a free flowing exhaust.

I have check with the plugs off that the pistons are moving up and down.

Is it possible they are not rising all the way and this is making the noise?

Ahh, that makes sense. Those small twins are very popular with the modder guys. Maybe someone installed those pod filters and chopped the exhaust but didn't properly jet the carbs. So now the bike is running drastically lean and you over heated it and seized the pistons. Once the bike cools off the pistons unstick, but the damage is done. I think you are going to have to open the engine to find out what's going on. If you know someone with a borescope you might want to look around inside each cylinder for evidence of seizure before you pull the head.

Piston slap from a seized piston, that has been broken free, sounds way different then a blown rod bearing.
Also, I've never had a seized piston engine that didn't also have really poor compression from galled rings and it would burn quite a bit of oil too.
Hard to tell what noise you are hearing but if you can get the engine running at a fast idle while pulling one plug wire off at a time, you'll hear rod knock change dramatically.

Ok So i began a strip down to the piston barrels and i found the following.
- The Cam shaft showing no signs of abnormal wear and there is no movement.
- The pistons themselves have no signs of wear.
- The piston rings are all still in place and in very good order.
- The cylinder walls are practically like mirrors.
- i did notice that i can lift the con rods up and down from the crank about 1 or 2mm ( i presume this would be rod knock )

Wear do i go from here?

Keep going...

You got a bottom end problem it seems. You are going to have to split the cases and see about finding a new crank & rods.

Cheers for the update mates!