Topic: 1982 CB650SC fuel tank

[moze229]

Hey all.  I know I'm sorta like the outcast around here because I have a Nighthawk and not the standard CB650   (Hey, at least I have the SOHC 4, right?)  But I have a question for you all regarding the fuel tank JUST IN CASE someone has tried this before.

I took on my bike project in 2010 as a big ol' piece.  Oil leaking everywhere, strong fuel smell, questionable brakes, etc.  I rebuilt everything - yes everything.  Every seal, gasket, filter, fluid - all done.  I even repainted a custom color and all is good right?  Well, a few months after all this is done I find that the fuel tank had pin holes.  (Of course it was AFTER the paint was on.)  Long story short, I've had two tanks on this thing and they both began leaking.  I didn't even bother painting the last one because I was afraid it would start leaking.  Good thing I didn't because just like the first one, pin holes on the low the side when on the kickstand.  The first one was sealed after the fact by me with tank sealer and it's ok, but I want one that has no holes.  The replacement that I bought ended up being worse than the first one.  This bike is 100% without these damn fuel tanks.   

These are hard tanks to find - it's a one year, one model tank.  The replacements are all questionable to begin with and expensive - they don't look any more promising than the ones that I have.  The 1983 Nighthawk model fuel tank looks similar - and I thought I've read where people have used those on the 82's but I'm not sure.  I can't find it anywhere now.  This would allow me to spend much less for a replacement, and have a larger pool to choose from.  1983 - 85 Nighthawks all used the same tank.  Just wondering if anyone had done this before or knew about it.  I can just buy one and try it, but I'd rather hear from a group to try and get some pointers first.  The mounting points are in the same places, but I need to sit one on the frame to make sure it doesn't interfere with the fuse box or anything.

Thanks.     

[cb650]

They are diff.  and wont "bolt" on.  But you can make anything fit.

[moze229]

Thanks.  I guess I'll have to just get one and see for myself.  I didn't figure it would work without some light modification, but was just wondering how involved that was going to be.  The most important parts are the mounts on the frame (of course) and the holes for the side panel tabs.  If the side panel tabs don't line up at all, then it's not really worth messing with. 

Thanks again.

[fizzlebottom]

I don't understand why you're going straight for a replacement when you can almost definitely get your original tank and the 2nd one repaired. Pinhole leaks don't mean the tank is finished. It means they have to be filled, covered, or repaired in some other way.

I think even if you have a metalworker or someone experienced in motorcycle fabrication go over it with a fine-toothed comb and fix the issues, you won't spend as much as you will getting a 3rd tank to fit correctly.

Explore your repair options a little further. Maybe you didn't get all of the rust out before lining the tank. Maybe the tank lining that you did failed in some way. The tank isn't dead yet.

[cb650]

I do have a 84 and looked at putting it on my 82 nitehawk.    Using another sohc4 650 tank would be easier.  Except Z. 

[SOHC]

My friend who is building a 76 750 into a bobber, had an 82 nitehawk tank just laying around, he thought it was the 83-85 tank, and ended up getting 2 wrong petcocks till we found out in fact it was a 82. (not sure how they differ but they didnt work)

We thought it was weird, how this was a 1 yr only tank, wish he could sell it too you but he modified it already, and patched the sending unit hole, etc, and he loves how it looks. If he knew it was a 1 yr only tank before he did the work to it he probably would have sold it.

[cb650]

if it had a sending unit it was a 83 and up.   82 didnt have it.

[SOHC]

if it had a sending unit it was a 83 and up.   82 didnt have it.

Not sure why the 83 petcock he ordered didnt work, cause thats what we thought it was, the bike thats sitting in his shed is a DOHC motor, but the frame year was before the DOHCs were made, so its a mix of parts then i guess, and when we looked at tanks on ebay, it matched the 82 for looks, and not the 83.

I wonder if the PO cut the sending unit in it?? to use the gauge??

[moze229]

Thanks for all of the input.  I've patched the original one temporarily until I decide what I'm going to do.  It's quite possible that I'm going to sell this one anyway - at an extreme loss now because of the problems.  I was originally in the market for a CB but I couldn't find one that someone didn't want an arm and leg for.  Had I been paying attention at the time that the cb650sc is a one year, one model bike, I would have passed.  At least most of the parts are interchangeable with the CB models.

Took it for a short 30 mile run today and it performed well.  Every time I ride it I want to keep it, then the thoughts of dealing with this stupid fuel tank issue comes back to haunt me.