Fork lower bearing track

[dickie]

Can anyone offer any tips or advice please?

I'm trying to fit a new lower bearing track to my series 2 Spanish forks and am failing miserably in what I consider should be a simple task.

I've heated the track as mush as I dare (actually a little beyond what I'd like as I've blued it), then dropped it on and tried to tap it down the last bit but it simply won't go.

I've measured the inside diameter of the track and it's 35.8mm versus 35.9mm of the fork, which seems like a reasonable but tight interference fit to me.

I can't think of anything else to do apart from try a track from a different source (I have scootopia). The last time I fitted an SR one and don't recall any problems.

[Fast n Furious]

Unfortunately, this is to be expected from time to time.
0.1mm shrink fit is a big ask here. I think if you did manage to get it on, it may possibly crack when it all cooled down.
If the tolerances are right then it should drop on with only moderate heat.
Sounds like you've about knackered this race anyway so i would recommend getting one from a different reputable source and see if the tolerances improve.

[dickie]

Unfortunately, this is to be expected from time to time.
0.1mm shrink fit is a big ask here. I think if you did manage to get it on, it may possibly crack when it all cooled down.
If the tolerances are right then it should drop on with only moderate heat.
Sounds like you've about knackered this race anyway so i would recommend getting one from a different reputable source and see if the tolerances improve.

Thanks, i wondered if that might be the case, but I'm an electrical engineer not a mechanical one so 0.1mm seemed like a little number to me. I'll get a new one from sr. As you say it's likely buggered anyway if i've blued it.

[dscscotty]

There are few steering bearing tracks in circulation that are slightly undersized, I've got around this with a dremmel/sanding band, been fine since!

[dickie]

There are few steering bearing tracks in circulation that are slightly undersized, I've got around this with a dremmel/sanding band, been fine since!

Cheers Scotty but i think I've wrecked it now. I'll order new tomorrow and measure before I fit this time.

[gp200ts1]

0.1mm is 4 thousandth of an inch so quite an interference fit on something with a small diameter. 1 thou would be a decent interference for for the steering race. I know there are some Vespa ones out there that look right but the fit is as you described. Perhaps someone has tried passing them off as Lambretta ones or mistakenly supplied one.

[Fast n Furious]

0.1mm is 4 thousandth of an inch so quite an interference fit on something with a small diameter. 1 thou would be a decent interference for for the steering race. I know there are some Vespa ones out there that look right but the fit is as you described. Perhaps someone has tried passing them off as Lambretta ones or mistakenly supplied one.

A definite possibility.
The number of times I've ordered lammy woodruff keys and got Vespa ones.......... Grrrr

[Ranburetta]

0.1mm is 4 thousandth of an inch so quite an interference fit on something with a small diameter. 1 thou would be a decent interference for for the steering race. I know there are some Vespa ones out there that look right but the fit is as you described. Perhaps someone has tried passing them off as Lambretta ones or mistakenly supplied one.

A definite possibility.
The number of times I've ordered lammy woodruff keys and got Vespa ones.......... Grrrr

But they are the same sir is the usual answer.

[dickie]

Sorted. Bought one from af which measured 36.05mm inside diameter. Scootopia was 35.8mm.

Af one was actually loose enough to fit by hand so i added some extra strong bearing retainer compound.

Thanks for advice

[Fast n Furious]

0.1mm is 4 thousandth of an inch so quite an interference fit on something with a small diameter. 1 thou would be a decent interference for for the steering race. I know there are some Vespa ones out there that look right but the fit is as you described. Perhaps someone has tried passing them off as Lambretta ones or mistakenly supplied one.

A definite possibility.
The number of times I've ordered lammy woodruff keys and got Vespa ones.......... Grrrr

But they are the same sir is the usual answer.

More like......"But they are the same sir" is the usual quote. "Getting a hitch home with the AA" is the usual answer!
I've had them where the height of the key is slightly higher than it should be. These keys prevent the taper from locking out, usually resulting in the flywheel coming loose and consequently wrecking the crank taper. Then, to add insult to injury the stress caused by the wrong key eventually splits the flywheel keyway down its length. Double bugger.
I'm no Vespanado, but these keys always seem to come from dealers who sell both Lammy and Vespa parts almost exclusively and are all probably made in Godknowswheristan.
My advice to anyone doing a build with a new Woodruff key is to do the fag paper test to ensure there is sufficient clearance at the top of the key when the flywheel nut is fully tightened. A simple, cost nowt test that is well worth the effort.