Degreasing two-stroke exhaust flange ready for welding

[mangocrazy]

I'm finally getting round to restoring the RD350LC I've owned since new. It was one of the very first batch in the country, but it's been left to gather dust in the back of the garage for the last 20+ years. The big problem I'm facing is that the LH barrel has a chunk chipped off the exhaust flange (where the exhaust pipe bolts on). The bike was punted from the rear on the LH exhaust and that caused a section of the flange (complete with exhaust stud) to break off. It was welded back on and lasted for about 10,000 miles, but just before I took it off the road the weld fractured and we're back to square one. Knowing what I know now, it was a pretty gash weld and it was amazing it lasted as long as it did.

The problem now is that the section that's broken away is effectively scrap - no way is it ever going back on. My local welders (JNC Welding in Sheffield) have advised me that the best way to approach this would be to build the missing section up in stages by gradually applying weld to the flange, then machining back where necessary. They've used this approach on all manner of stuff including Porsche engine blocks, and it certainly seems the obvious way to go.

But before they can start building up weld to the required area, that part of the barrel/flange needs to be properly cleaned. As you all know, it's not possible (or even remotely sensible) to try and weld to a contaminated substrate. And this bit of aluminium alloy has had oil-laden two-stroke exhaust blow-by passing over it for the last 10,000 miles. How would you go about prepping and cleaning this piece of ali ready for welding?

I appreciate that photos would be a really good idea here, and I'll add them as soon as I can, but in general what would get a fractured crystalline alloy casting clean enough to weld to? I've thought about concentrated sugar soap solution, degreasing in Jizer, dipping in acid, steam cleaning and a few other things. I asked a local plating firm who do zinc passivation if they could dip the barrel in their pickling solution, but they advised me that the hydrochloric would eat the aluminium for breakfast. So that's a no, then.

For those not familiar with Elsies, they are a liquid-cooled (hence LC - Elsie - geddit?) two stroke motor with an aluminium block with steel liners, so whatever I use has to tolerate both steel and aluminium. All suggestions gratefully received...

 

[penfold]

You could try baking it for a few days but the only reliable means of doing it that I'm aware of is to repeatedly grind it back to fresh metal and weld over it until it welds cleanly. Depending on the alloy even a good weld may not be very clean.

 

[Wendelspanswick]

I'd go with a steam clean followed by repeated soaking in acetone, you don't want anything too aggressive that will attack the base metals.

 

[Woody.v8]

I would visit my local cylinder head place or engine re-conditioners and slip em a drink to put it in the hot wash tank.

 

[addjunkie]

Im in the grind back camp, but acetone can be usful for cleaning. As for the welding find some one who as done things like jap bikes before, metal quality of the last one i welded was utter carbage

 

[Robotstar5]

I used to de-coke the baffles from my strokers in Caustic Soda solution, not sure how it affects Aluminium though.

 

[Chris Stevens]

Welded loads of 2T cylinders. If you get it steamed cleaned or pressure washed with TFR, then grind back the damaged area with a carbide burr, it will weld very easily. They tend to use a lot of silicon in cylinder castings, which makes them easy to weld.

 

[mangocrazy]

Welded loads of 2T cylinders. If you get it steamed cleaned or pressure washed with TFR, then grind back the damaged area with a carbide burr, it will weld very easily. They tend to use a lot of silicon in cylinder castings, which makes them easy to weld.

Pardon my ignorance, but what is TFR?

 

[Woody.v8]

Traffic film remover

 

[mangocrazy]

I would visit my local cylinder head place or engine re-conditioners and slip em a drink to put it in the hot wash tank.

Thanks Woody - sounds like a great idea.

 

[MattF]

I used to de-coke the baffles from my strokers in Caustic Soda solution, not sure how it affects Aluminium though.

Caustic eats aluminium.

 

[Chris Stevens]

If the majority of the exhaust gasket recess is still there, its simply a matter of steam cleaning or pressure washing, grinding back the area needing repair with a carbide burr, building up with weld, and reinstating the rebuilt gasket recess area, with an end cut carbide burr in a die grinder. I would tend to use 5346 rod, as its easier to work than 4043, which tends to clog burrs. If almost all the gasket recess is gone, and it needs to be set up in a mill and machined, a used cylinder would probably cost less money.

 

[mangocrazy]

Chris, the exhaust gasket recess is about half gone, but my tame welders don't see that as a problem. I've found an engine reconditioning place in Sheffield (just round the back of the Hillsborough stadium) and they're going to give the barrels an extended soak in their hot tank. I'll see what state they're in after that before I decide what to do next, but dichloromethane (is that the same as methylene chloride?) sounds like it should do the trick. Thanks everyone for all the suggestions, it's much appreciated. I've certainly got no shortage of options...

If a used barrel had been available for sensible money, I'd have probably gone down that route but individual barrels in a scarcely viable state ('tuned' by unknown hands and on their 4th oversize) are still fetching around £150 a side on ebay. A pair of barrels with pistons can fetch upwards of £500, so fixing the ones I've got is almost certainly preferable.

 

[pedrobedro]

I used to de-coke the baffles from my strokers in Caustic Soda solution, not sure how it affects Aluminium though.

It eats it quicker than acid and has to be thoroughly washed off as, like the Energizer bunny it just keeps going.

 

[jordan1]

Chris, the exhaust gasket recess is about half gone, but my tame welders don't see that as a problem. I've found an engine reconditioning place in Sheffield (just round the back of the Hillsborough stadium) and they're going to give the barrels an extended soak in their hot tank. I'll see what state they're in after that before I decide what to do next, but dichloromethane (is that the same as methylene chloride?) sounds like it should do the trick. Thanks everyone for all the suggestions, it's much appreciated. I've certainly got no shortage of options...

If a used barrel had been available for sensible money, I'd have probably gone down that route but individual barrels in a scarcely viable state ('tuned' by unknown hands and on their 4th oversize) are still fetching around £150 a side on ebay. A pair of barrels with pistons can fetch upwards of £500, so fixing the ones I've got is almost certainly preferable.

I would think that by the time you have finished with cleaning, welding and machining [if necessary] a replacement cylinder must be a viable option, I've refurbished Yam YPVS's and think you should get a decent barrel if you wait a while, there are specialist Yam breakers out there. If you repair, you still have no guarantee it will last. Try fred2stroke or yamahardbreakers.

 

[mangocrazy]

I would think that by the time you have finished with cleaning, welding and machining [if necessary] a replacement cylinder must be a viable option, I've refurbished Yam YPVS's and think you should get a decent barrel if you wait a while, there are specialist Yam breakers out there. If you repair, you still have no guarantee it will last. Try fred2stroke or yamahardbreakers.

I'll give those breakers a go, but I'd say that original 350LC barrels are MUCH harder to get hold of in decent nick and at sensible prices than YPVS barrels. There are plenty of those about, as the YPVS was made from 1983 to about 1995. The original LC was only on sale for about 3 years before the YPVS came along. What makes it really annoying is that I have a brand new RH LC barrel, but it's the LH one I need.

 

[Chris Stevens]

Why not see if Banshee cylinders will fit? I would guess cheap and easily available from US?

 

[dobbslc]

There'll be nothing cheap about going the Banshee route

 

[Chris Stevens]

There'll be nothing cheap about going the Banshee route

£31 for 2 cylinders and a head seems very reasonable to me: http://www.ebay.co.uk/itm/Banshee-3...395548?hash=item235fd11ddc:g:fngAAOSwHPlWgZ1q

 

[dobbslc]

I was thinking of the ones they tune the nuts off. Stan Stevens does work on these I think. Ridiculous power if you want it........