Changing engine capacity and DVLA

[Biker9090]

I have a CZ125 with shot crank bearings meaning a full rebuild. I have the parts to make it a 175 (crank and top end).

What's the score with changing engine capacity like this and the DVLA? I'm going to declare the mods to the insurers as there's no way I'm risking that. Can I tax, mot insure and ride it as is until I get a new V5? They apparently need a copy of rhe engine parts receipt?

[Tango13]

If you're keeping the same engine number I wouldn't bother telling the DVLA, you're doing the right thing by telling your insurance company but the DVLA? fk 'em!!

I swapped an entire engine on my Triumph years back and never bothered telling the DVLA on the grounds that they're so fking incompetent the bike would've probably come back registered as an oil tanker, space shuttle or an old persons retirement complex!

[Dog Star]

On this subject a mate of mine had a GSXR600 and it was registered as a Leyland Atlantean bus!

Not sure what the score with taxing it was - but he’s in the motor trade and does have a somewhat revisionist attitude to motoring law and paperwork on his own stuff.

[Rubin215]

Biker9090 said:

I have a CZ125 with shot crank bearings meaning a full rebuild. I have the parts to make it a 175 (crank and top end).

What's the score with changing engine capacity like this and the DVLA? I'm going to declare the mods to the insurers as there's no way I'm risking that. Can I tax, mot insure and ride it as is until I get a new V5? They apparently need a copy of rhe engine parts receipt?

Write them a letter explaining that you cannot provide any receipts, they will be fine with it.

DVLA, for all the bureaucracy they are mired in, like a good letter.

[sixor8]

Changing engine capacity or even the whole engine isn't usually an issue really. But in this case, taking it to a 175cc would change the taxation class of the bike. Motorcycles, even now, are still charged VED purely on engine capacity, they don't bother with the emission data like for all cars, and like many other countries.

Since <151cc is £22 p.a. (currently), 151cc to 400cc is £47 p.a. The amount charged is irrelevant really, it's just that the 'computer' probably wants more data due to it being a change in VED band.

[KTMsm]

It's very much luck of the draw

I've played with a lot of cars, after swapping the engine for a larger one sometimes they will change it immediately without question and sometimes they will ask for loads of information including an engineer's report - so I stopped bothering to tell them

On CO2 based tax they will not change the class regardless, higher or lower

I would assume they would on cc based tax but they might not

[DJP]

If you're keeping the same engine number then I wouldn't be telling anyone at all. There'll be minimal performance difference and the chances of anyone stripping an ancient CZ to check the capacity is precisely zero.

[catso]

As above, for a 50cc increase I might be tempted to 'forget' to inform anyone.

But when I built my Ducati Monster (from parts), the frame and therefore the identity was from a 600cc and I made it into a 900.

They asked for proof of the engine swap and I sent them a copy of the receipt from a bike breaker for the 900cc engine which they accepted, though the cynic in me thinks that they're less inclined to care if you're increasing the tax class?

Actually I've got the same to do with my current project, and old Landrover which I'm currently rebuilding as I'll be replacing the old, wheezy 2.5L 4 cylinder diesel with a 3.5L V8 petrol, again the only proof I've got is a receipt for the engine.

[rigga]

DJP said:

If you're keeping the same engine number then I wouldn't be telling anyone at all. There'll be minimal performance difference and the chances of anyone stripping an ancient CZ to check the capacity is precisely zero.

This all day long.