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Tank doesn't seem to fit

Smithandbacon

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I just acquired a 1980 cb750K and the tank doesn't seem to fit. The two ears up front seem wider than the bushel no mounts slightly and the bolt down near seat is maybe two inches from the frame where it bolts down. Is this normal. ? The middle of tank is bottoming out on frame tube.


 
Somebody has likely subbed the wrong tank, they pretty much do NOT interchange from model to model. People swear they interchange and it's outright BS.

Pics might clear that up instantly.............
 
265725d502a86c92314be290dfdb5dc5.jpg



 
Looks like correct K tank and possibly K frame but everything has been messed with. The front tank mounts on tank have been moved apart, they are no longer in parallel. Normally they are dead square to each other and how they would be narrower rather than like too wide on yours. Obviously can't say what lies under tank.

Hack work.
 
The explanation for that would likely come from the same planet that altered to where the tank does not sit down all the way over the frame too. Pull the rubbers and make sure somebody hasn't cut the frame stubs the rubbers go over.

Can you pic the frame with tank off and also pic the slot inside tank? Something is seriously whacky there. Has someone changed the coils?
 
Something still wrong there. In your pic 3 you can see the back tab that back of tank mounts to and the hole directly below it that the mount bolt threads into. But can't hit the mark due to tank hitting frame tube. In pic #9 you can clearly see how wide the tank mounts up front have been spread compared to front frame mounts and possible the bottom of tank has been pushed out (for more volume?) to now hit the top frame member. That is NOT correct. Frame looks like a K one from the sideplates that passenger pegs and exhaust back bolts to. I dunno. I have suspected the frames are all the same except for the mounting lugs and tabs that match the different models. Maybe something being you are in Japan is in wonkyland there. Maybe a 400 pound chick sat on the tank. Maybe using a soft wood dowel of some sort you can center inside tank and pound lightly to move tank inside back up to just clear. Inside moving back in and up away from frame would pull the mounting notches more in parallel.

That one'll be up to you..................up to you to determine where your distortion is coming from. I wonder if your front tank mount bosses are in the correct place but if a K frame they should be right. The rear mount looks right.

I'd be taking your tank with you to match other K tanks you can run across. Maybe they have bike scrapyards there too?

I'm betting on tank being the issue.
 
Vin tell you frame year and model? Have you verified tank year and model?

Not all tanks fit all frames... for instance. A 76-78 auto tank will fit a 69-78k frame, but a 69-78k tank will not fit a 76-78 auto frame


 
Not that, the riveted on plate, it details the exact model of frame like K, or F or C. Looks to be a K though by the rear exhaust mounting plates.

Like I said tank, it appears to have been squished from the top, that pulls the bushing slots apart and out of square and the bottom then bulges out like the later pic in post #9 seems to show. You can clearly see the area where the tank bottom strikes the frame rails and not right.

One fix given in post #11 or another tank in your future likely.
 
It's a k. But the tank seems to have distorted somehow.

Next question. I was offered a cb900 tank. I'll have to check the year. But was told it's about an in h longer. Any experiences?


 
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