How do you stop aluminium fork tubes cancer ?

[bullmad24]

Recently purchased a 1992 RM 250 and the fork tubes are all cancered and i also have another set on my other bike the same im just wondering if theres a way to stop it from getting any worse or why its happening thanks.

[alexbrown64]

Im working on the fork tubes on my boys rm80 tonight.  Same thing as yours except his are 35 years old.  Its usually the clear coat on the tubes that protects the alloy.  I brushed his with some paint stripper and it just peeled away.  Only left it on a few seconds and washed it straight off.  Depending on how bad the alloy is, a very light sand with fine wet and dry or 0000 wire wool and then alloy polish should bring them up.  Then, up to you but you can clear coat them again.  I am just leaving the boys fork legs polished.   Dont quote me on yours... test a small inconspicuous spot to see if you have clear coat and to see how easily it comes off.
Cheers,
Alex

[Tossa]

I agree looks like a clear coat problem, but I could be wrong it's the same sort of thing you get with the whitening of the clear coat on car paint.  But this is from a distance of 3000kms

[Momus]

The seat has a bad case too...


The tubes look weathered and in need of a refinish. Judging by the rusty pinch bolt it has been washed with a pretty caustic detergent.

[SON]

Water blast them then recoat in clear

[bullmad24]

Righto thanks guys I need to rebuild the forks anyway so i'll blast and reclear them thanks again.

[Bikeaholic]

I see this quite a bit on jobs I do for people. It is the clear coat breaking down. It also happens on engine cases. Alloy cases on the early Hondas are a perfect example. Once the moisture is able to get under the clear coat it starts to oxidise the alloy. As already mentioned the clear coat has to be removed and alloy cleaned/polished. Either then keep the polish up or re clear coat them. As they say nothing lasts forever

[grouty]

I had the same issue on my old KLX250. When I finally got round to restoring it a few years ago I just used paint stripper, wire wooled them and used a buffer on my electric drill to shine them up. I finished it with a few hours of 'Solvol Autosol' alloy polish.
I was expecting to have to re-do them every now and again, but after 2 1/2 years of hard use in all weathers (mainly winter) with much salt on the roads they have not dulled at all. No corrosion either. All I do after washing the bike is to spray it all with 'Duck Oil'.


Still going strong .....

[Nathan S]

Drawn/extruded and spun aluminium ally tubes on USD uppers are a very different material than the cast/pressure cast lowers on a set of RWU forks.

The USD uppers corrode badly and quickly - if the cause of the failure is as simple as a failure in the anodising, then they are incredibly sensitive to having good anodizing... I have three sets of early USDs with perfect chrome but utterly rooted uppers, and gave away another set a few weeks back.

[William Doe]

Buy a vintage bike  as Nathan says you wont get the problems you do with that modern stuff.

[oldfart]

By buffing them up using the correct compounds ( wax )  it provides a coating that will protect them from the elements

[JIM77]

By buffing them up using the correct compounds ( wax )  it provides a coating that will protect them from the elements

Tectyl 151, used to be my choice when working with alloys, but they don't make it anymore. Can you Tell me more about what your using when polishing?

[oldfart]

Denim cloth 1inch wide with Brown compound  and  sisal  3inch wide with Green. You can't mix cutting compounds up with wheels . Put a piece of plastic hose over the adpt shaft on your bench grinder and any slip ups  will have no effect on polished part.
 

[GMC]

I see this quite a bit on jobs I do for people. It is the clear coat breaking down. It also happens on engine cases. Alloy cases on the early Hondas are a perfect example. Once the moisture is able to get under the clear coat it starts to oxidise the alloy. As already mentioned the clear coat has to be removed and alloy cleaned/polished. Either then keep the polish up or re clear coat them. As they say nothing lasts forever

I think Bikeholic is onto it.

Alluminium forms oxides that protect it as soon as air touches it however it may be moisture that has gotten under the coating that forms the corrosion.
I'm surprised that this can happen with anodizing but not surprised at all with paint.

[evo550]

I'm with Nathan on this one, those tubes look they are on the way out.
Don't know how many of those early '90's upper fork tubes I've seen where the Ali just turns to powder.