Hey,
It is possible to restore some of the power on post A4 models by replacing the carb tops.

Models A1-A4 produced around 110bhp. This was reduced to a mere 92bhp with the introduction of the A5. Don't believe people who say you won't notice the difference and that the A5 is plenty powerful - it is NOT and you WILL.
The unrestricted version from the earlier models are directly interchangeable and do not have the raised section. Make sure you order the tops from an A4 or earlier ( the part number you want is 16005-1056). 

US bikes are not afflicted by this disease....

Very lucky, it is amazing the difference it makes!!

US bikes are not afflicted by this disease....

Are you sure Tony? See below from service manual:
These figures don't have the (U) prefix so I assume are applicable to US models.
A1 - A4   80.9kW @ 9500 RPM
A5 - A8   68.4 kW @ 9000 RPM
A9 - A11 80.9kW @ 9000 RPM does have prefix (U)

A5 - A8 seems to be the odd one out; strange.

Not trying to start anything.......................

Regards, Russell

Are you sure Tony? See below from service manual:
These figures don't have the (U) prefix so I assume are applicable to US models.
A1 - A4   80.9kW @ 9500 RPM
A5 - A8   68.4 kW @ 9000 RPM
A9 - A11 80.9kW @ 9000 RPM does have prefix (U)

A5 - A8 seems to be the odd one out; strange.

Not trying to start anything.......................

Regards, Russell

Reasonably confident anyway.... 

My memory has been known to fail but it seems that I recall this topic coming up her and there in the decade I've hung out here and and I seem to recall that US models did not have these restricted caps otherwise this would be one super popular mod and that one of the reasons for the big differences in HP numbers was due to how the HP was measured between various countries.

Yeah could be a typo in the manual, seems odd to derate the A5 - A8 models (in the middle of the run) only. Steve In Sunny FLA would probably know.

Regards, Russell

yeah - i'm sure. they're all the same, and that 108 / 92 hp difference was just that they originally posted HP at the crank, then started measuring at the rear wheel. We saw the 300 hp chevy engine drop to 210 with the same change. Steve

I have a set of Euro-Carbs somewhere in a box, back in time I posted pics with a compare, the euro lids were restrictive and also the center "spring guide" was longer, which stopped the slide about 2mm lower than our domestic version, there was a difference in performance with the slide restriction height.

I been looking for some stuff lately in the huge parts supply I have still packed, when I find them I'll post the compare again.

I just had another set of carbs come in from the Netherlands today. I haven't taken them apart, but if they're restricted, I'll get a pic. Steve

I just had another set of carbs come in from the Netherlands today. I haven't taken them apart, but if they're restricted, I'll get a pic. Steve

OMG, you are internationally known now. I guess next time I call you your assistant will say, "Have your people contact our people and we will see if we can get you an appointment".

Jim - you have people? 

BTW, these carbs have the same tops as ours do. only difference is the carb heater hoses on the bottom -  Steve

OMG, you are internationally known now.....

I'm still tickled each and every time I'm contacted for one of my kits from Europe or Australia.... 

Jim - you have people? 

BTW, these carbs have the same tops as ours do. only difference is the carb heater hoses on the bottom -  Steve

Steve, do you know what model/  year the carbs are from? just out of intrest

yes, a 95.

I have done several sets from europe, I have yet to see any restricted cap carbs.

One thing I've noticed is that all the euro carbs I've done have the crappy brass needle jets. They're know for excessive wear in short miles, which kills fuel economy. You euro guys ought to order the American needle jets; same dimensions, but I think they're stainless steel - certainly much longer lasting than brass. Steve

Thanks, my 92 and 01 models had the restricted tops, my first c10 a A3 hadnt. Yes, its the shipping costs that are the problem even on small items. Maybe santa will bring me somestainless ones lol

The 94 on had the restricted carb tops in some countries.
UK bikes were included but many people fitted the carb tops from the 86-93 carbs.
If you had the later tops on carbs from a 92 then someone swapped them out before you bought it.

If you want to you can just remove the ridge bits with a Dremel but be careful to leave the inside of the caps smooth as a babys botty.
Any rough bits will tear the diaphragms.
For the best increase in power couple the carb top mod with freer flowing mufflers.

Yes i have installed a full motad stainless exhaust so that and carb top mod should be just the job !

Yes i have installed a full motad stainless exhaust so that and carb top mod should be just the job !

Do you have any pictures or info (website etc) on that Motad exhaust system you can share?

hi Tony, i got mine direct from motad, part number-  NGTR1K  COST £576, WWW.motad.co.uk
Pic of silencer/muffler fitted,  and pic of pipework plus completly fitted to bike 

Available in the USA from David Silver Spares.
http://www.davidsilverspares.com/motad/part_193341/
US$735 for a complete stainless system.

The headers are the same as my older N-Eta system but the new mufflers are stainless and chromed.
Some dealers still have stock of the N-Eta mufflers here in the UK.
They more closely echo the OEM mufflers in style.