Baffles?

[MrDavo]

I’ve never had the baffles out of my HM300s, but I assume that they have been in there for decades.

The bike runs fine, and isn’t too loud for me. However I was wondering firstly if you can renew the fibreglass packing, and secondly whether they are supposed to be replaced at specific mileages or intervals?

[K2-K6]

I don't know the answer regarding the 300 series pipes and if you can repack them.

But on both two and four stroke pipes that use packing like this they always benefit from having the packing in good order.  It makes them run better at low rpm,  more crisp and responsive and feel less "baggy" in low end throttle response. 
I suppose "more concise" might describe the feeling I'm aiming at with better torque response at lower throttle opening.

Worth exploring I think,  if they are able to be dismantled.

[Green1]

From memory the fiberglass is just wrapped around the baffle and held in place with a small amount of wire threaded through the holes in the steel baffle, How much was on there when new I have know idea as when I looked at them they were in a rather sorry state.

[MrDavo]

Does anyone know what to get?

I'll have a dig in the garage and look for an old glass fibre repair kit, otherwise its eBay or off to Hellfords.

[taysidedragon]

I think you need special exhaust packing. Google for exhaust specialists and you can buy it from them.

I don't think ordinary fibreglass mat is fireproof!

[MrDavo]

Flames out of the pipes would be funny but leave a nasty blue mark! Thankyou for saving me from myself, that's why I ask on here first. 

Google found me this:

https://www.dirtbikexpress.co.uk/bike_parts/motocross_exhausts/exhaust_accessories/rfx_2_stroke_flat_exhaust_packing?gclid=EAIaIQobChMI4YCu8_mJ2wIVDt0bCh0nggM6EAQYASABEgIHe_D_BwE