Hi all, i was hoping someone would be able to help with with an issue im having with my new bike, its a Honda cm400 which, when it was made in the early 80's put out 42 BHP according to honda, at the crank presumably.

Nearly 30 years on do you think it is likley to still need restriction to put it under 33 bhp at the rear wheel on a dyno?

Im a bit worried that putting in the standard carb washer type of restrictor will put it way under 33 bhp if it adds to other age related factors which will have reduced the power over time.

The other thing is that some of these restrictor kits ive seen for sale are for use on cm400, 450 and 500 models (that is the same washers to fit all 3), from the look of and placement of the washers im guessing that that they just reduce the fuel mix flow from the carbs to the cylinders, my worry is that if these washers are sized to cut a 500cc bike down to 33bhp that they would put a smaller capacity bike well under 33bhp, do i have that right or could one size washer have the same effect on all three capacities?

This restriction lark is looking like it will be a right pain , 33bhp i dont mind a bit, but getting there without going way too far is looking like it could be far more complicated than i had anticipated

if it bothers you that much , you need to find a shop with a dyno & get it run on that to see what its actually producing. of course i'm never , ever , going to tell you that most officials wont know the difference between restricted or non restricted-that would be crazy for me to imply in any way. the restriction kits are not an exact science & yes the effect on a 400cc bike would probably be more than a 500cc

Thanks DP, i think i will dyno run before i do anything else, its proving a bit hard to find a dyno place tho. As far as using it is concerned i think its very likley thats its no longer making over 33bhp at the back wheel anyway, and if it is it wont be by much. Its more for peace of mind than anything, i plan to travel alot on it and i dont want any awkward situations, mind you in 3 years of riding i havent been pulled over once :p