yamaha yz250h rear suspension....

[VMX Andrew]

hi guys ....need some help......im having some problems with my rear suspension..today i tried to connect the rear shock to the swingarm but the sleeves will not go in where the shaft goes through the swingarm they are correct size and all but they seem a touch too small... maybe i need a special press to push them through...any tips would be helpful....                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

[Lozza]

Heat up the swingarm area and put the sleeve in the freezer  overnight.With one hot and one cold they should fit together.
HTH

[VMX Andrew]

thanks lozza...what i meant was the sleeve is slightly too big by about half a millimetre...anyway ill try that and see what happens....

[Rosco400]

Rule of thumb on a press fit is one thou per inch. 40 thou is = to 1 mm, 20 thou is .5 mm, based on the diameter of bush/sleeve being .5mm to big for the hole and guessing the sleeve is probably only about 25mm diameter there is no way that will fit. Maximum difference i would guess on this press fit should be about one thou or .04mm, have you used set of inside micrometers and measured id of swingarm holes and outside diameter of bush/sleeve, if close to these tolerances, i would put a chamfer on lead in of bush/sleeve and pull in with threaded bar with nut either end making sure pulls up square. Light heat on the swing arm would help because this should expand bore thou or two correct me if I'm wrong lozza

[YZ250H]

Hey Andrew.  Where did you get those sleeves from ??  I can't find them on any Yamaha parts diagrams.  They seem to be part of the swingarm.  I had to drill mine out  as the pin and sleeves etc were siezed together.  Very hard to take bike apart if shock won't separate from swingarm.  I have bought a new pin etc.  I was going to get some new sleeves turned up at a machine shop, but if you can buy them I won't bother.  Any chance a part number   If not would you mind taking a few measurements with the calipers ?? Any help appreciated.

Cheers

[VMX Andrew]

mate i had the very same problem.when i went to take the shock off, the sleeves were seized into the swingarm so i had to hacksaw one of them off and bash the shit out of it.but i should have taken my time with them because yamaha dont stock them anymore.... i didnt know at the time...so what i done i waited and found a nice shock and swingarm for sale in the classifieds section on this website a few months back .....i got lucky soaked the top of the swingarm and sleeves in diesel ovenite and the next day they popped out no worries should have done that in the first place with the originals....but these sleeves i got off this swingarm are made out of different materials,they look like they are stainless steel and are home made...and also they are off a yz465h 81model.i do have one old one laying around in the back shed may be i could get one of my work mates to make a set up for you in the lathe....i work for a big nestle food factory....

[YZ250H]

Andrew,

I'm pretty sure those sleeves are a tight fit so they don't flog out the aluminium in the swingarm.  I don't think I want to find another swing arm, so I reckon I might try to get some made.  I don't expect you to make them for me.  If you could get the calipers out and measure one for me I would really appreciate it.  I can get them made up locally.  I have the remains of one that I drilled out, so I have the outside dimension.  If you could give me the others we would be in business.   I that part on the 465 and the 250 are the same.   Is your 250 a goer ??
Cheers

[evo550]

My 2 cents worth,

I got a new bush for the bottom of the shock, took it, the shock and the swingarm to my local machinist
They then pressed out the bush from the shock and the brass bush from the swing arm, turned down new brass inserts for the swingarm pressed them in, turned down a new pin to suit the new bottom shock bush, and pressed in the shock bush, all for about $50,
Snug as a bug in a rug.

[YZ250H]

Sounds like what I think I'll end up doing.  Just need the inserts.  Bought a new yamaha pin.

[VMX Andrew]

my 250H is a goer ive spent a lot of cash on her and cant wait to get it out there amongst the heaven vmx crew next year. ;)the only measurements i can take are of the main shaft and one sleeve which i got off the old one.....the new sleeves are all back together on the bike...

[YZ250H]

The old sleeve would be Ok I reckon Andrew.  I could do the same as Evo550, but there are a number of different degrees of press fit I think.  Just how tight is tight enough ?  My shock needs new bushes as well.  I assume they can be replaced with turned down neoprene (?)

[Lozza]

If you want a 'set and forget' type set up use lead/phosphor bronze it's hard and slippery.Then drill some cross holes and pack with bearing grease.

[evo550]

The machinist should know what tolerances each bit needs.
You should supply him with a new genuine yamaha shock bush, so he can work out the right diameter of the pin first.
He will then work out the i.d. of the brass bushes for the swingarm based on the pin size, and will allow for a small amount of shrinkage in the i.d of the bushes when the are pressed into the swingarm. The o.d of the bushes are pretty irrelivant as the hole in the swingarm will probaly need to be redrilled as the alloy tends to elongate over time, if this is not done and the holes are elongated then it can distort the brass bush when it is pressed into place.
I even got mine to put a thread on the end of my pin so i could fit a lock nut instead of the split pin, that kept coming out.

[YZ250H]

Evo,

Trouble is I don't have a new shock bush and by the sounds of things I'm not likely to find one.  I've got an NOS pin.  I'll trot myself down to the local machinist and see what he can do for me.  Sounds like a very common problem with these things.  I like Lozza's set and forget solution.  I will suggest it to the guy when I see him.

Thanks fellas 

[worms]

Hi guys
had the same problem on the 125 project but was able to use a brass sleeve straiht off the self from eng works, freezed it for a couple of hours and went in nice and tight, try your local shop before you get it made only cost $5 each side

cheers
trev