Quick Q About Restricted Bikes

Does the restricted power output for A2 licenses apply for rear wheel horsepower or power at the engine/crankshaft?

Mainly because the Ninja 250R is 33bhp at the engine but only around 26bhp at the rear wheel, however the restricted 400’s get dyno tested on rear wheel being 33bhp. (Another reason being bikes such as the DRZ400S/SM are about 35bhp at the rear wheel so could you just about get away with them being slightly detuned to hit 33rwhp?)

Thanks for any help!

May be wrong, but I think the DVLA have a list of “all” acceptable bikes/restirictor set ups.

Just don’t look for bike over, say, 10/12 years old. Apparently they don’t think any of those are still running

IIRC all measurements are done at the crankshaft.


IIRC all measurements are done at the crankshaft.*

That’s handy as nearly all manufacturers show their power at the crank not the rear wheel. Just need to read the catalogues.

Also means you could ride a '60’s Triumph Bonneville on a restricted licence. 100 mph+ machine, no brakes worth having, a frame with a hinge in the middle and skinny little tyres, and you can get it on a classic policy if you don’t commute.

That’s so sensible.

would be an interesting commute on one though :slight_smile:

Who says bureaucrats don’t like an easy life! :slight_smile:

Thanks for the info Giuliano, hope you are good by the way!

My only doubt with this is that all the restricted 400’s get washers in the carbs or throttle pins and are dyno-ed at the rear wheel to 33hp. I dont recall anybody with a 400cc bike dyno testing it at the crank [im not sure if most Dyno stations even have the nescessary equipment to do this?]

i will try to ring DVLA and their useless automated phone system to find out!

Are you sure they are not dynoed to 33bhp - an estimate of the drive train loss? I am sure that is what the restrictor kit designers do as otherwise there would be no need to restrict the 500cc versions of the X9 and Nexus at all as they must be under 33 at the rear wheel.For example, if you know a bike has 50bhp at the crank because the manufacturer says so, and the dyno measures 40bhp at the rear wheel, it must be possible to reduce the rear wheel bhp to a point where the crank bhp is likely to be less than 33.