Weeping oil tank patch

So I finally got tired of wiping the sweat of oil off the bottom of the frame rails and decided to try the CNW style tank mod, worked like a charm.

Cut off the lower mounting boss, ground flat and welded a steel plate over the area to take care of any of the fractures as well as give a nice flat surface which will sit on a .5" rubber pad



While I had the tank off I also welded the fractured rear mounting tang

Very nice repair. I'm aware that this seems to be a common problem but am dumbfounded that the Commando I'm restoring doesn't have a hint of a crack on any of the oil tank mounts. Am I just lucky with this one?

Anglophile said:

Very nice repair. I'm aware that this seems to be a common problem but am dumbfounded that the Commando I'm restoring doesn't have a hint of a crack on any of the oil tank mounts. Am I just lucky with this one?

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Lucky... so far.

Here's how I mounted mine.

combat-proddy-build-begins-t4186.html?hilit=oil%20tank&start=120#p59866

Notice that I did not use the bottom mount at all.

Anglophile said:

Very nice repair. I'm aware that this seems to be a common problem but am dumbfounded that the Commando I'm restoring doesn't have a hint of a crack on any of the oil tank mounts. Am I just lucky with this one?

Click to expand...

From what I've been told, the upper tank mounts will fracture as soon as the bottom lug goes... which apparently is quite frequent, a quick fix is to simply use a zip tie around the oil cap neck and upper frame rail. What's really insidious however are the micro fatigue fractures commonly present around the bottom lug, these are difficult to see but will cause oil to weep out. Eliminating the bottom lug and supporting with a rubber pad seems to do the trick.

Welded mine over 30 years ago, still good. Both my top mounts are solid, been alright so far.

Anglophile said:

Very nice repair. I'm aware that this seems to be a common problem but am dumbfounded that the Commando I'm restoring doesn't have a hint of a crack on any of the oil tank mounts. Am I just lucky with this one?

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Nope. My MKIII had a perfect tank with no cracks. I still did the mod though just in case.

Replaced all the oil lines in prep for the rally. Observed oil return all good etc, so off I went through the neighborhood for a quick spin to ensure all was ok . Sitting at the traffic light my heart skipped when I saw oil spray all over the right exhaust and oil dripping on the road under the bike. luckily only 1/2 mile from home so navigated gingerly back to the garage. Found the culprit to be leaking where the oil return pipe enters the tank. Dont know if I can get my welder to repair before the rally as everyone's schedule is crazy so will JBweld/Magic Bond do the trick here to get me through the week or is there something better? I can braze or solder but I dont know if thats acceptable where weld exists already? I can get a pic later but heres the area in question.

Braze will be OK to repair the crack, the original is brazed. Grind out as much of the original in the crack area. A Dremel tool is ideal for this. Give the tank a real good clean out first, rinse several times in water to de-fume any residue, braze it up, let it cool and re-rinse several times as some scale may be released from the heat internally.

Mick

Thanks ML for the tips but luckily I wont need to do a repair. I missed diagnosed the leak its not a crack it coming from the oil cap. With frustration and darkness last night I got it all wrong. I had the oil tank breather line capped and now I see thats a bad idea.Theres too much pressure in the oil tank now lifting the oilcap causing oil to mist out. Im going to go with a catch can or something instead of capping the breather and see how that works.

I use a little K&N breather filter and let it dangle down behind the transmission. This is on the pipe that once went to the carb airbox.

http://www.summitracing.com/parts/KNN-62-1000/



I think CNW has something similar. Not much oil comes out but I'm not a drip counter.

speirmoor said:

Thanks ML for the tips but luckily I wont need to do a repair. I missed diagnosed the leak its not a crack it coming from the oil cap. With frustration and darkness last night I got it all wrong. I had the oil tank breather line capped and now I see thats a bad idea.Theres too much pressure in the oil tank now lifting the oilcap causing oil to mist out. Im going to go with a catch can or something instead of capping the breather and see how that works.

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Glad to hear it's not cracked. i'm surprised that more of us don't have oil leaks from that location actually, as it seems like a good place for microcracks to propogate.

Rocky Point Cycles sells silicone gaskets for the oil cap seal cheap ($2.75). Replaced my cork one and I've had no more leaks from there.

Cheers,

- HJ

batrider said:

I use a little K&N breather filter and let it dangle down behind the transmission. This is on the pipe that once went to the carb airbox.

http://www.summitracing.com/parts/KNN-62-1000/

I think CNW has something similar. Not much oil comes out but I'm not a drip counter.

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That'll do Cheers!