TOPIC:

I've never encountered a heat barrier under my tanks. I have had 3 now. 79,80,81.

I have NO idea why your tank won't fit. With the crap mess of coils and wiring under my current tank you'd think I was a candidate for a poorly fitting tank but nope... like a glove.

Do you want me to post pictures of the underside of my tank and frame for comparison?

To the best of my knowledge, your fuel tank is for a 1980 KZ1300 B2. A 1980 KZ1000 MKII does have a similar fuel tank, of the same color, but there are some differences. But, I could be wrong.

As far as I know, only the B2 had the heat barrier on the bottom of the tank. This was put on at the factory because the fairing tended to trap heat from the motor.

To LedKZ1300: Yes, please. Any pictures of other tanks are helpful.

MZ, as Globemaster stated, pretty certain that your tank is from a B2 and not from KZ1000 MkII, the 1000 MkII tank has its fuel tap located at the very rear LH side (as Z1 & KZ900) , and there is no fuel sender on the RH side. Keep at it, I'm sure you'll get it sorted.
Cheers Tim

Tried to get some measurements of the tunnel on my spare tank, not easy to measure accurately with an old tape so maybe not much help but I'll put it on anyway.

My 79 tank is full and has fresh paint so I can't flip that one over until its empty. Here are a few pictures of my 81 tank underside and frame for comparison.