YZ250 F 1979 Rear Brake backing plate or advice on how to fix seized bush...

[oldyzman]

Hello, I am looking for above as my one is all good except the axle bushing does nor swivel in the backing plate - result is that the rear suspension is binding...

Cheers Brett

[lms6201]

try 200 deg in the oven for an hour or two , might loosen it

[oldyzman]

Thanks, will try
Brett

[oldyzman]

Gday Curley, Thanks for getting back to me, cannot see how to attach the PIC.
Cheers Brett

[jimg1au]

i think the backing plates have magnesium stamped into them.they are bigger brakes than std yamaha stuff.i have 2 rear wheels complete with brakes.i think quicky had 1 for sale some months back with a pic
cheers
jim

[jimg1au]

all these bike use the same hub
Part # = 483-25311-13-98
Part Description = HUB,REAR
Model Count = 22
IT250F 1979 250 IT250 Dual-Purpose
IT250G 1980 250 IT250 Dual-Purpose
IT400C 1976 400 IT400 Dual-Purpose
IT400F 1979 400 IT400 Dual-Purpose
IT425G 1980 425 IT425 Dual-Purpose
MX250B 1975 250 MX250 Off-Road
MX400B 1975 400 MX400 Off-Road
TT500C 1976 500 TT500 Off-Road
TT500D 1977 500 TT500 Off-Road
TT500F 1979 500 TT500 Off-Road
TT500G 1980 500 TT500 Off-Road
TT500H 1981 500 TT500 Off-Road
YZ250A 1974 250 YZ250 Competition Motocross
YZ250C 1976 250 YZ250 Competition Motocross
YZ250D 1977 250 YZ250 Competition Motocross
YZ250E 1978 250 YZ250 Competition Motocross
YZ250F 1979 250 YZ250 Competition Motocross
YZ360A 1974 360 YZ360 Competition Motocross
YZ400C 1976 400 YZ400 Competition Motocross
YZ400D 1977 400 YZ400 Competition Motocross
YZ400E 1978 400 YZ400 Competition Motocross
YZ400F 1979 400 YZ400 Competition Motocross

[oldyzman]

GdayIMS,  thanks for the advice re the heat but it did not seem to work
Brett

[oldyzman]

Gday Jim, I believe the hub on the backwheel is the same, however the backingplate on saya YZ400D has a slot init which keys to the swingarm to stop it twisting where the YZ250F 1979 has a tab on the bottom, and a rod runs back to the frame near the footpeg, the bushing allows the backing plate to swivel not effecting suspension...
Cheers Brett

[jimg1au]

brett
some do some dont just check out yamaha parts in the usa.i have a it and a yz wheel bothe the same with lug for brake stay

[rocketfrog]

I use two carefully selected sockets, ie one to support the housing and one snug in the bearing, then put in the vice to press - or find a suitable bolt, nut and washers as required to press out old brg. Then fit heim brg, might need to ream housing slight o/s to fit.

[rocketfrog]

oops, thought you meant the torque arm bushing. nevertheless the axle bush comes out the same way, maybe apply load and allow soak o/night with wd or similar?

[oldyzman]

Gday rocketfrog, it would seem that there is a steel sleeve that presses into the casting, then another bush runs inside that...
Really want to se a good one then i will know what to aim for...
Brett

[jimg1au]

brett
i have 2 rear wheels with what you whant to look at,give me a ring and come and have a look
cheers
jim

[rocketfrog]

Ahh, I am on the same page now. You need to separate the plain bush (axle spacer) from the outer bush (this one is in contact with the backing plate and features a flange on the inside face of the backing plate) yes? I have one siezed up solid just like yours, I wound up cutting a slot through the inside bush and collapsing it to remove th sucker. After that I cleaned out the pitting on I/D of the outer bush with a reamer and had to get a new inner machined to replace it (Brass). The inner bush serves to space the distance between the R/H wheel bearing and the outer axle spacer so as the backing plate does not bind when the axle is torqued. This means the overall length of the inner bush should exceed the length of the outer bush marginally. The outer bush should be able to be recovered with a little reworking and a new inner could be fabricated a reasonable cost or even for nix if you are fortunate to find an old axle spacer that you can modify to replace the inner you remove and have access to a small lathe. PS, file some flats on the head/flange of the outer bush, this makes it easy to grip in your vice, and will not alter the fit or function of the part. It also reduces the chance of creating unneccessary damage to the finish on the O/D of the bush. Hope this helps mate, you could of course seek some NOS replacement parts, but I reckon the name of the game is keeping the costs under control. 

[oldyzman]

Gday Rocket,
Thanks for that very detailed description of works, your bang on the money, Had a call tonite re another backing plate which is swiveling OK.  I reckon i will give the re bush a go only if this other one doesn't work out. One question mate, Did you use brass or phosphur bronze?
Cheers again.... Brett