Z1OwnersClub GB

Am I right in thinking that the main fuse should be 20amp as I keep blowing them

My Z900 has a 20A, I don't know what your bike is though.

Sounds like you have a short somewhere

20a is the main fuse size. If it doesn't blow with the ignition off then there must be a short a short after the ignition switch. Normal place that wears is where the ignition connector block enters the headlight shell. If the headlight shell doesn't have the rubber grommet fitted the wiring can wear on the headlight shell hole edge. Although both the headlight shell and ignition switch turn in unison with the handlebars as the main loom enters the same hole but is restricted from moving by the headstock which means all the wiring entering the headlight shell flexs in the hole when the bars are turned. If it wears through the outer sleeving and grounds to earth on the shell, pop goes the main fuse.

Cannot see a rubber for the head light opening listed in the parts book

the grommet being referred to is 92071-1008 but this part wasn't used until Z1000. Depending on which headlight shell you have, it might not fit

Used from 76 on Z650 through Z1000. NO. 92071-1008
I've got a Z650 and A4 that has it fitted. Both bike are 100% original. Doesn't show it on the parts diagrams for either bike but does show it on the 1977 Z1000.
Have you checked if that's the cause of your issue? If it is then cheap work around is slitting the length of some soft tubing and cutting to length. Handy because it can be fitted without having to dismantle everything.

There are 2 similar posts, i replied to the other one, as also had blowing 20a main fuse on my A4, however it coincided with faulty voltage reg ( 15.7v) which i replaced with combined unit and that seemed to stop issue, however it may well be attributed to short on headlight bowl, no idea if mine original or been replaced but the large opening has a turned edge to prevent schaffing, so no grommet needed.

z2.john wrote:the grommet being referred to is 92071-1008 but this part wasn't used until Z1000. Depending on which headlight shell you have, it might not fit

I'd agree with Z2.John here, an academic point really, but A4's did not have this grommet fitted as standard. If your A4 has one then it has been fitted as an "extra", which isn't a bad thing by any means !!