carvedtangent3
New Member
I am planning a cb750 build and i like the looks of the 1978 gas tank. Will it fit on any other frame from 69-78? Thank you
Cb750 tank compatablility
- Thread starter carvedtangent3
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carnivorous chicken
Over 1,000 Posts
Not sure about cut-off years and I'm assuming others will chime in, but the 77-78 tanks won't fit with earlier bikes -- 75 and 76 that I know of, and I'm guessing earlier bikes -- because of petcock placement.
Carvedtangent, which '78 tank are you referring to?
The '77-'78 "F" model tanks wont fit anything but a '77-'78 "F" model frame. Not without some frame work anyway. (they're physically longer)
The '77-'78 "K" model tank will cross over much easier, all the mounts are the same. But as chicken mentioned, the fueltap placement is slightly different between the two.
Basically, the later tank is physically wider, and the fueltap reflects that. The early tanks have the fueltap approx. 1" closer to the tank centerline than the later tanks.
Below is a pic of the underside of a '75 K tank (left) and a '78 K tank (right)...
These are both spare tanks for me, and I never tried to actually fit the '75 tank to my '78 K model. And as you can see, there may be some clearance issues on the underside. Especially if fitting an early tank to a later frame. I ran a tape measure from the front mount to the back of the rear mount, and between the front mounts. And both measured up the same, +/- 1/8". If you want/need more specific measurements, just holler
The '77-'78 "F" model tanks wont fit anything but a '77-'78 "F" model frame. Not without some frame work anyway. (they're physically longer)
The '77-'78 "K" model tank will cross over much easier, all the mounts are the same. But as chicken mentioned, the fueltap placement is slightly different between the two.
Basically, the later tank is physically wider, and the fueltap reflects that. The early tanks have the fueltap approx. 1" closer to the tank centerline than the later tanks.
Below is a pic of the underside of a '75 K tank (left) and a '78 K tank (right)...
These are both spare tanks for me, and I never tried to actually fit the '75 tank to my '78 K model. And as you can see, there may be some clearance issues on the underside. Especially if fitting an early tank to a later frame. I ran a tape measure from the front mount to the back of the rear mount, and between the front mounts. And both measured up the same, +/- 1/8". If you want/need more specific measurements, just holler
carvedtangent3
New Member
Thank you for your detailed answer. So you mentioned the petcock placement. Would it hit anything or would i just have to run a longer line?Redbird said:Carvedtangent, which '78 tank are you referring to?
The '77-'78 "F" model tanks wont fit anything but a '77-'78 "F" model frame. Not without some frame work anyway. (they're physically longer)
The '77-'78 "K" model tank will cross over much easier, all the mounts are the same. But as chicken mentioned, the fueltap placement is slightly different between the two.
Basically, the later tank is physically wider, and the fueltap reflects that. The early tanks have the fueltap approx. 1" closer to the tank centerline than the later tanks.
Below is a pic of the underside of a '75 K tank (left) and a '78 K tank (right)...
These are both spare tanks for me, and I never tried to actually fit the '75 tank to my '78 K model. And as you can see, there may be some clearance issues on the underside. Especially if fitting an early tank to a later frame. I ran a tape measure from the front mount to the back of the rear mount, and between the front mounts. And both measured up the same, +/- 1/8". If you want/need more specific measurements, just holler
carnivorous chicken
Over 1,000 Posts
Petcock hits the carbs, won't work.
Chicken, I'm not arguing, just trying to understand for my own curiosity.
Are the carbs placed different between the early and later years? Is it the difference in the round top carbs and/or the keyhole carbs?
Seeing the width difference for myself, I could see how the narrower early tank/fueltap might interfere with the later carbs, but the wider '77-78 tank seems like it would clear.
Again, not "callin BS" or anything, (you've obviously had more experience with it than I) just trying to wrap my head around it
Are the carbs placed different between the early and later years? Is it the difference in the round top carbs and/or the keyhole carbs?
Seeing the width difference for myself, I could see how the narrower early tank/fueltap might interfere with the later carbs, but the wider '77-78 tank seems like it would clear.
Again, not "callin BS" or anything, (you've obviously had more experience with it than I) just trying to wrap my head around it
carnivorous chicken
Over 1,000 Posts
I'm not getting testy, just telling you the deal -- but to be honest it's been a few years and I can't remember what the switch was I tried to make and what the issue was. I think the tanks sit lower and the petcock is designed differently, and therein lies the rub.
I didn't suspect you were, I just wanted to make sure you knew I wasn't eithercarnivorous chicken said:
Gotchya, I didn't think about a drop in the sides of the tank. "therein lies the rub"... pun intended?
Tangent, it seems Chicken has the scoop. If you want to fight with the fitment issues, I'm still willing to take measurements of either tank and/or measurements of the fitment on my '78 750K. Just holler