Benno

I persisted with the original carb, swapped jets, modified the slide etc and still wasn't totally happy, bolted on the Mikuni and happy days.

I don't think a 42mm carb is too big for a standard or slightly modded evo 80". You could always swap jet sizes if too rich for a stock motor.

cheers

DocGreen

if you are talking 40 vs 42 Mikuni ( and not 40mm CV ), you will find very little difference in performance at your level.

The 42 has around 15cfm more flow, and is a more refined carb' , and would easily support ~115hp .

If you have to buy one, go for the 42mm (future proof ), otherwise use what you have.

A 40mm CV would also be perfect for a 1340 .

Then you get another EVO 80 inch same as first one. Put a Mikuni 42 on & tune that to perfection. Will be no difference. But if you race the two off the lights, the one with cv will jump away, provided both riders about same weight same skill . As you just can match constant velocity off the mark under load with a rider controlled throttle .   But if the two bikes side by side & rolling at same speed & both on the rev, then both open up full at same time . They would just Be even. If stock carb on just save your.  money.

Only thing is Mikuni give detailed instruction how to tune the.   carb & not everyone knows how to tune a cv properly Bobby Woods has some different fuel curve needles & other parts to convert to Holley. main jets that increase in thou also you an  change the size of the air bleed. & few other things.

but in the ends carb just adds fuel & air it is not some magic wand 

Good luck

I want to leave it stock, but it's a bit pretty ordinary response wise.

Cheers

The HS40 Mikuni was the earlier offering from Mikuni that came in a dedicated kit for Harley Davidson, it was pretty much a TM, rectangular toggle operated slide and very good fuel/air control. Prior to that you could get a VM38/40/44 round slide for your Harley, these were pull cable in slide operated and better than most else at that time. I remember i think it was the old Motorcycle World in Waymouth or Pirie st [Williams also had them] that stocked VM's at a dollar a mm, $40 for a 40mm.

Now, or should i say for many years now we have been able to get the HSR42/45/48 they are excellent in any application, 42mm for up to 98/100" and 45 for over 100",48 for big inch motors.

We now see some 42's with carriage wear in the body, these are usually very early ones with ridiculous miles on them, so beware when buying second hand, not everything lasts forever no matter how well made. The early 40's could suffer from stiff operation, this was usually caused by the return spring being set on the stiffest of three settings and poor servicing, not because of the carbs design.

Harley SE sold Kehin 44 and 51mm CV's  in the early days, these were excellent performance carbs that were capable of making big horsepower, but these were eventually dropped by SE and only the Mikuni 42/45 was offered as performance carburetors. If you can lay your hands on an early CV make sure it has a manifold with it as these are very rare.

Spend some money and just put a new 42 on it and get it tuned, this will give the best long lasting result.

Cheers.

Could I ask if you know someone in Brisbane/SE Qld region that you would happy recommend for tuning the CV carb.

Go see Red Fred.

Cheers.

same conclusion as Doc Green....

years ago after farting around with CV for seemingly forever with modest results, i scored an old early model HSR42 (throttle linkages opposite side) off ebay for $40 sold as parts.....rebuilt it with kit from MikuniOz in Townsville (very helpful) & never looked back !

as DC said "happy days"