I put the cheap ass gel battery that I bought into the bike, took ages to start after sitting the whole winter not running for 3 months. Even using prime. In the old days I used to drain my float bowl but I'm too lazy these days, and also we don't have ethanol in our fuel .
New battery handle that no problem, I would try to start it twice, and then let the battery recover for a few minutes while I theft in the garage and then came back to try it again.
Anyhow, during this time I noticed a little trail of brake fluid coming from my sight glass. Measured it to check it is the 18 mm standard diameter, and ordered five of them from AliExpress for a few bucks. Hopefully they fit... I might try to buy a proper viton o-ring rather than go with what will probably be a cheap and nasty supplied o-ring