The Danish mk1

[mads_christ]

Yes it runs on all four...

The brakes are stock. So definitely needs an upgrade!

[Notso Swift]

Is the spark at the right time though, just check the leads are 1342 not 1432 or something minor
Otherwise fuel for those two, either way it sounds like they are not pulling their weight

First step with brakes for bike carbs (or ITB's) is a vacuum accumulator and 1 way valve, same as they use on turbos

[mads_christ]

I need to check the leads. But I'm pretty sure they are in the right order...
Some carb-fiddling might solve the problem. Perhaps the needle setting aren't identical on all four...

Silly question: vacuum accumulator? Where can I find one? Are they typically used in cars? I have no idea what they are...

[Notso Swift]

THis sort of thing, but you also need a 1 way valve because the bike carbs have a bit of trouble holding enough volume for the booster
Vacuum Reservoir BMW F01 F02 750 I 06 08 7571303 05 Turbo | eBay

Use some like this to collect it
JDM Aluminum Turbo Wastegate Boost Vacuum Intake Manifold 6 Port 1 8 NPT Black | eBay