Project Katmandu: GS rebuild

[MattW]

I've just got my hands on a vapour blaster, needs a little TLC before I can use it but brings ally parts up like new.

Ooh - jealous I am

 

[Rob Farmer]

Rob, how does a vapour blaster work? Is it just water or do you use some medium as well? I have seen the results first hand and it is bloody impressive.

You put a blast medium in the tank and the pump circulates it at high pressure. There's also an airline in there to give it some more welly. It's the same as this

http://www.rileysurfaceworld.co.uk/machines/23198.htm

 

[fayeslane]

Is the medium glass bead like a dry blaster or specific to vapour blasting. The "I could make one of those" fairy is sitting on my shoulder

 

[Rob Farmer]

The pump is a special rubber coated one to protect it from the abrasive medium I think that will be your biggest problem. Apart from that it's just a 1.5kw pump. It's the pump bearings and control panel that's fried on the one I've got.

 

[Rob Farmer]

Ooh - jealous I am

You haven't any ally to clean on an oilhead.

 

[MattW]

You haven't any ally to clean on an oilhead.

Apart from the rims which are unanodised raw alloy (mine's an early 1100) and the hubs which are covered in severely bubbled powdercoat (along with a few other bubbled bits which would benefit from stripping back).

Then of course I've not always just had new(ish) stuff like oilheads - there's always 'the next bike' ...

Anyway, who said you had to justify all the tools you want

 

[fayeslane]

The pump is a special rubber coated one to protect it from the abrasive medium I think that will be your biggest problem. Apart from that it's just a 1.5kw pump. It's the pump bearings and control panel that's fried on the one I've got.

I was thinking if I used bicarbonate soda as the medium then the pump internals would be OK for a while. Not sure if soda would be aggressive enough for some jobs though. I've got a spare household presssure pump here that might do.

 

[Rob Farmer]

That sounds good. I guess you just need a pump with a decent pumping head on it and a nozzle that will handle the slurry.

or You could make your own using a pressure washer and one of these kits http://www.alexshanks.com/karcher-sandblasting-kit-p407 using bicarb instead of sand.

 

[fayeslane]

Thanks Rob, I didn't know about those. I have an industrial type pressure washer so that would be the most cost effective option. I'll get on to it and post results -good or bad (certainly messy ).

 

[pete.keys]

vapour blasting

Rob and Fayeslane: great discussion on vapour blasting. I wish I had one local - but Rob you might find me turning up on your doorstep any day now

Would it be ok to do a bevel drive with one. I have cleaned mine by hand as a I have been worried that any sort of blasting might affect the seals and I didn't really want to rebuild it as I believe its a pretty specialist and costly job.

 

[Rob Farmer]

Would it be ok to do a bevel drive with one. I have cleaned mine by hand as a I have been worried that any sort of blasting might affect the seals and I didn't really want to rebuild it as I believe its a pretty specialist and costly job.

You would need to strip it down to blast it using beads or the vapour blaster but using the pressure washer with bicarbonate of soda wouldn't be any worse than jet washing your bike. I'm curious to see if it works.

 

[Deleted account 111026]

I bead-blast BMW airheads all the time when doing renovations and I can't believe people have had their engines and gearboxes blasted without dismantling them first.
I always fully dismantle engines and gearboxes before blasting, then afterwards everything is pressure and hand washed. Even with special aluminium blanking plates fitted to the casings, there is always evidence of beads in the interieur.
Unfortunately they don't always get picked up by the oil filter but get into the main and big-end bearings, and bushes, which then start grinding the shafts, etc.

 

[Rob Farmer]

I don't think anybody here is suggesting that beadblasting without stripping down is the way to go.

 

[Deleted account 111026]

I think sycomoto on his 'Camille re-build' thread has had his blasted whole.

 

[(RIP) pastyman]

I tried the soda blasting route on my RT using a blast pot connected to a compressor. got the proper stuff from Frost but it had very little effect except on the likes of the carbs ,which it brought up well. the barrels and diff it made no difference.
I decided to go down the blasting route using a lovcal firm and aluminium oxide. I taped everything up then taped again. the barrels I didnt go too mad on as they were off the crankcase( which I was'nt doing) and they went through a proper cleaning process before new valve guides etc were fitted.
the finish was great and almost factory new, no sign of blasting material anywhere it shouldnt have been. I suppose it remains to be seen whether the engine destroys itself but I dont see any reason why it should though I must stress the blaster never went anywhere near the crankcase.

 

[Deleted account 111026]

You've done it correctly, stripped, masked, cleaned thoroughly and re-fitted.
You probably noticed how microscopically small some of the 'dust' particles can be, they really can find their way into the smallest hole.

 

[sycomoto]

nothing got into camille

i've checked and apart from abit of glass dust around the starter motor and a bit on the clutch nothing got inside. Camilles a rally bike so everything is pretty well sealed, even when i removed the front cover i only found a very small amount of dust at the top around the electrical connectors. The guys who did my work specialize in vintage car blasting and while i was there there was an old 4 1/2 bentley engine complete waiting for blasting so they must be good.

 

[Deleted account 111026]

So you only found glass dust in three different areas.

 

[sycomoto]

Yep

All none criticle areas where dust and grit normally get if you off road your gs. As I said camille is a rally bike so spent time blasting through dust sand and gravel. Under my ownership she's been off roaded and I'm not talking about a dusty road but propper shitty stuff. When I sealed the engine off for blasting I did a propper job hence I've no grit or dust inside. I'd suggest your ally blanking plates need binning or you find a better way of sealing your engine as my method of old socks, machined plastic blanking plugs and duct tape seem to have done a far better job.

 

[Deleted account 111026]

I only blast empty casings, the ally plates just stop them filling up, although it always amazes me how much gets through the tiniest gap.
I've never blasted a complete engine, too afraid of the liabilities if I made a mistake with the masking!
Sounds like yours will be O.K., you're just braver than me! (Have you any spare old socks?).