Making a bike ULEZ compliant

[SirFallalot]

I've seen the list of passed bikes which leads me to believe that my 94 CB400 might pass, however most are higher cc, this is obviously always a risk.
https://www.bikerandbike.co.uk/list-pre-euro-3-motorcycles-with-ulez-exemptions/

I've tried out some some recent bikes and still prefer mine, so thought about taking the test as it is sometimes convenient for me to go to the zone. Also I've accidentally wandered in it before

So, what reversible modifications could be done, if at all possible? Fuel mixture? Fuel type? Timing? My exhaust is the original one piece stainless and I'd rather not change or cut it up. I've heard they will tune it themselves to try to get it through the test, however then I won't know how to put it back when not riding in London
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Lexmoto Valiant 125; 94 CB400; 96 CB750F2; 81 CB750 (restoring, lol not gonna happen); 2001 ZX9R(It's about to go :c); 2012 R1200R; 2015 R1200RS

[Bhud]

The best action you could take is to call them (the testing garage). Ask your questions and they will explain everything on the phone.

A lot of people have put their bikes through this test and passed. They may have had to service their fuelling to make their bikes run properly, before this test. As they paid £179 for each bike, they want their certificates to last as long as possible before the goalposts are moved again and the certificate becomes worthless.

In these times, some press officer at TfL or a govt body could easily type a search query into Google and find enough meat there to misquote and misconstrue some basic advice on how to service a bike to make it run properly as an attempt to circumvent the system to get "polluting" bikes through. In fact, I'm sure they'll try that when the time comes around to add pages to their "consultation". They will call it a day's work. At the end of the day, people want their certificates to last for as long as possible.

[MarJay]

Nap. Just buy a new bike.

There is only one place that does the test. They charge something like £175 for the priviledge, and they are likely booked up from now until 2050. Even if you get a slot, get the bike there and they stick it on the dyno, they'll mess with the bike and might not even be able to make it pass.

So, looking at the list of bikes that have been re-evaluated since the test was instigated, they are pretty much all 2001 onwards. The occasional 1998 bike, but these all seem to be bikes with pre-emptive emissions standards like Hondas and BMWs.

My standard VFR with EFI, a catalytic converter and PAIR system won't pass apparently, and that's a bike that is 6 years more modern than your CB sadly.

The problem as I see it is that bikes that meet modern emissions regs aren't as good to ride as older bikes. The fuelling is jerky and there is a disconnect between your right wrist and what happens on the road. I reckon the way to tell if a bike will pass the ULEZ is probably to ride it, and if it rides that way (IE badly) it's either already OK or got half a chance of passing.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.