Polyethylene plastics

[alexbrown64]

I will probably have a few Q's on this forum as i am rebuilding a 1979 RM80N.  Anyway, plastics are original but look nasty.  There are some cracks.  Are most of the soft oily plastics that the mx bikes run polyethylene?  Polyethylene is oily, tough, cant be glued, melts when heated and flexible.  I am just wondering if anyone has much luck plastic welding them the correct colour and how they come up after.  I was thinking of taking some shavings from the back mudguard where it cant be seen and using them to fill in the cracks by heating with a soldering gun and melting it together and then sanding it back to shape before polishing it up.  Or, does anyone know of a plastic welder in Perth or have other techniques.

Cheers,
Alex

[John Orchard]

Japanese mx bike plastics are polypropylene.  Can be welded & polished.

[oldfart]

Problem is if they are badly weathered the wax is all but gone ( chalky )  which makes it impossible to weld  and will split again .
Shave off a piece, and heat it with a soldering iron and you will see if go waxy this means it has got too hot .
PPE welding is precise welding job .... meaning too much heat will fork the joint.

[alexbrown64]

Thanks for the reply's.  I have had a look at some cheap plastic welding air guns on ebay about 60 bucks.  I also just bought an old 1979 rm400 side cover and i will use that to practice welding on and to cut strips off to weld my rm80 plastic cracks.  Worth a try.

[micko]

Motorcycle Panel and Paint in Osborne Park (perth) does plastic welding, ask for Simon

[Rossvickicampbell]

I think many years ago I used those guys to repair a VFR 750 side panel which had cracked when it fell off the stand.  Had a mark (weld??) on the inside but spotless repair on the outside where it counted.

[alexbrown64]

Thanks Micko, i will give Simon a call if i get stuck fixing these plastics.  He quoted me $660 to spray the outside of my rm80b tank recently and that was with me supplying all the decals.  He does a great job but sometimes its out of my budget for an old mini motocrosser.
Roscoe, those bike fairings are ABS and can be welded up really good but need repainting.  I used to have the old VF750F that had some repairs as the original fairings cost more than the bike was worth.
I never did get that rm400 plastic sidecover.... i ended up with a 79 rm50 side cover for $21.  This is going to be my donor plastic and practice piece for welding.
I sanded one side panel, masked it up and painted the number plate background with plastic satin black spray paint.  Only it was too shiny so.  I have now ordered some VHT plastic and bumper paint which is satin so i will post up results.
I also ordered 1979 rm250 side cover decal stripes and will modify them to suit the 80 as you cant get the side cover stripes for the 80 anywhere.
Cheers,
Alex