Galvanic corrosion ?

Fast Eddie said:
I’ve run bare alloy fork top nuts for years without issue (standard on Maxton fork conversions). I’ve been using a thin smear of silicone grease and all is good.

There’s no harm in anodising if you so wish, but it’s not strictly necessary.
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The strongest aluminium is usually 4000 series which contains about 4% copper. It does not usually anodise very well. It often ends up looking like crap.If you put a very small drop of caustic sode solution on it, and the drop turns black, the aluminium contains copper and is 4000 series.. If the drop turns white, the aluminium contains magnesium and is 5000 series. The series numbering is the system used by the Aluminium Development Corporation. 6000 and 7000 series are the really good stuff. I usually try to get 6061, when making bits out of plate.
Your fork nuts would probably be made from 4000 series aluminium. Casting aluminiums are usually high in silicon. They are a different series to structural aluminium.
 
I had a corrosion problem with Mikuni carbs on a T250 Suzuki race bike I built. I ran it on methanol and did not drain the carbs after riding it. The next time I rode the bike, it seized near the end of a long straight. I was lucky, I did not bend the crank - the bike went about 20 metres with the rear wheel locked. When I pulled the bowls off the carbs, I found the whit crap had formed and blocked the jets. There are two drain screws ot the bottom of the bowls - when I took them to drill them, I found they were already drilled. The Japanese are not stupid. With my Seeley 850, I always remove the jet covers after I ride the bike. Modern petrols often contain ethanol which is chemically similar to methanol. I think the zinc content in the aluminium might be the source of the problem.
 
My Honda wept like a pansy, once I'd got it running. But in fairness, I don't think a previous owner's chisel was the factory specified tool for separating the cylinder head.:mad:
 
Mart UK said:
My Honda wept like a pansy, once I'd got it running. But in fairness, I don't think a previous owner's chisel was the factory specified tool for separating the cylinder head.:mad:
Click to expand...
PO was simply trying to address the design flaw regarding the lack of automatic external corrosion protection …
 
Re the video, I don't understand why one would heat the exhaust nut and cool the head.
If you heat the exhaust nut it will increase in OD, making the thread tighter. Cooling the head will only make it worse. I'm not surprised that it didn't work, no matter how many F bombs were dropped.
If you could heat the head while keeping nut cool then that would be going the right way to make the threads loose.
Just the same as heating case and keeping a bearing cool to drop in.
The exhaust nut is the bearing, the head is the case.

Glen
 
worntorn said:
Re the video, I don't understand why one would heat the exhaust nut and cool the head.
If you heat the exhaust nut it will increase in OD, making the thread tighter. Cooling the head will only make it worse. I'm not surprised that it didn't work, no matter how many F bombs were dropped.
If you could heat the head while keeping nut cool then that would be going the right way to make the threads loose.
Just the same as heating case and keeping a bearing cool to drop in.
The exhaust nut is the bearing, the head is the case.

Glen
Click to expand...
You do know the thread on a BMW exhaust rose is internal ?
The exhaust rose on a BMW are regarded as a service item by some
Just cut them off and replace
 
On balance, given the heat and carbon and how alloy can weld itself to alloy, I would personally not use alloy nuts.

Comnoz proved that the stainless nuts coefficient of expansion was actually very well matched to the alloy head.

Can’t see any point in risking all those alloy to alloy issues personally.
 
Fast Eddie said:
On balance, given the heat and carbon and how alloy can weld itself to alloy, I would personally not use alloy nuts.

Comnoz proved that the stainless nuts coefficient of expansion was actually very well matched to the alloy head.

Can’t see any point in risking all those alloy to alloy issues personally.
Click to expand...
I think the Japanese solution is better
Just bolt the pipes on with a flange and studs and nuts ,not the he low quality Suzuki bolts that corrode into the head
 
baz said:
You do know the thread on a BMW exhaust rose is internal ?
The exhaust rose on a BMW are regarded as a service item by some
Just cut them off and replace
Click to expand...
Same as a Norton?

Oh , looked up a photo. It is opposite to a Norton. I should have looked at that before commenting!

Glen
 
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Another reason not to use alloy nuts is that you will need to use something better than a standard peg wrench on them.
I had to make one for the RGM alloy nuts. On the other hand, if you want a really light bike you find yourself doing all sorts of silly things.

Screenshot_20240201_193336_Chrome.jpg
Screenshot_20240201_193313_Chrome.jpg
 
commandofastback said:
The creator of Werner is a guy called Rötger Feldmann and some of the storys are based on the things that happened during the plumber-apprenticeship of his brother Andy.

Andy has been fiddling around with almost everything that has an engine and he now runs the most entertaining Youtube channel I know (in german I am afraid)

50cc Zündapps, NSUs, BSAs, a Triumph Twin engined ice sled, and one of the last projects was a Norton engined dragster with a Druin Compressor.... that didnt work...and another compressor..... that didnt work....

Click to expand...

.... and now that Torfrock music is playing in my skull 😜
 
Little Update on the exhaust nuts. I fitted the aluminium nuts from Andy Molnar with a healthy blob of copper antiseize and no locking tabs. 2000kms without any sort of movement on the nuts. They are not as pretty as the originals but for me they do the job perfectly.
 
Mine had the lock tabs and I knew no better whilst I was tightening, then retightening, until the roses settled at tight. The tabs broke off on both and vibrated loudly. Having just got it tight, I didn't fancy undoing the exhaust to remove them. I managed to get a smear of RTV in, to stick them to the exhaust rose. Sorted. Some day, a future owner may well post on here to ask the purpose of the 'washers'!
 
Mart UK said:
Mine had the lock tabs and I knew no better whilst I was tightening, then retightening, until the roses settled at tight. The tabs broke off on both and vibrated loudly. Having just got it tight, I didn't fancy undoing the exhaust to remove them. I managed to get a smear of RTV in, to stick them to the exhaust rose. Sorted. Some day, a future owner may well post on here to ask the purpose of the 'washers'!
Click to expand...
When new and flat they are of no value. If you bend a slight "S" into them before putting them on, they will not rattle and they will prevent the roses from unscrewing. Of course, the free end must be bent to lock the roses after tightening and straightened before unscrewing and I consider them a "last line of defense". The roses coming a little loose is much better than them coming very loose.
 

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