Thanks guys, this is boring detective work compared to carbon dating a Bultaco, but we’re getting there.
Yes Hardo, found it on the mudguard schematic,
I had only looked on the muffler and frame schematics.
I thought it odd that this part wasn’t shown despite being on several models.
So it’s called a Muffler stay
Part # = 35011-1154
Part Description = MUFFLER STAY
Model Count = 4
KX250-C1 83 250 KX250 MOTOCROSS
KX250-C2 84 250 KX250 MOTOCROSS
KX500-A1 83 500 KX500 MOTOCROSS
KX500-A2 84 500 KX500 MOTOCROSS
It comes up as a different part No to my 87 model, which is different to the 86 model, which is different again to the 85 model!!!!
Thanks for the offer of a loaner but if someone can supply me these dimensions that should be all I need.
It may also be handy if someone can confirm the distance between the 2 mounting holes on the muffler too.