Z1OwnersClub GB

Having trouble with the e-start on the 78 Z1000B2, it kicks into life fine but the bike battery can barely get it going for more than a few seconds. When i jump it off the car while its ticking over, it would try to stall the car I need a bout 3 k on the car tach and then the starter spins like it should. Have done it with the battery connected and with the jump cables straight to the battery cables, same results. Any ideas what would be drawing that much juice when I use the e-start ?

First I'd double check all connections are tight & CLEAN... especially the H/DUTY leads

Then check the state of the brushes. They could be badly worn or very dirty, a good strip & clean could work wonders. Brushes can be replaced, Z1 Enterprises or Z-Power should be able to help you.

As above - dirty/worn brushes and commutator and general internal wear, worn armature bushes or build up of carbon dust.
Also check for a bad live lead, loose connection or frayed wire leading to excess resistance .
NEVER jump start off a car battery though, you risk burning out the starter and overloading the wiring.

Also check the engine earth. If this isn't as good as the feed to the starter motor then you can have bad performance. ( A previous owner had used the wrong type of wire (non flex) on my B1 and this broke gradually over time causing the starter motor to run poorly)

Regarding using a car battery, zed1015 is correct. What you are doing is putting more power into the system, what goes in must come out and this could mean breaking down other electrical circuits

I clean carbon brushes and commutator with a bit of emery cloth, and give it all
a quick spray with Maplin's contact cleaner.
Work's well.

If you want to replace with new brush set,
Z-Power £28.95 incl. delivery without discount
£26.06 with club member discount @ 10%.

Thanks guys for the replies. I had already taken the power lead and the earth lead off and cleaned those and re terminated a couple of dirty old connections. I will pull the starter now and check the brushes.
I really didnt know about the car battery thing, hate to admit it here, Ive been doing that for decades if i didnt have another bike to jump off. Needless to say I wont be doing that again!