Basic carb settings (long)

I need to set the carb up on the Rotax, it is a 4 valve OHC 500 single in
a reasonable state of tune, runing a fairly open exhaust, MX cam, flowed
head etc.

It was all set up and ready to go when I first brought it,however I have
had to fit a silencer to passify the MOT man, this meansthat although it
runs, ticks over, and revs cleanly it is running really rich, so where do
I start? I guess I can go out and buy a bunch of main jets, play for ages
and then find a local dyno and play some more however this is a bit hit
and miss, and removing and replacing the carb is a two hour job (nightmare
from hell) so is there an easy way to determining basic settings?

I did find a really good website the other day where you enter the bore, stroke
carb size rev range etc, and it gave you the ideal exhaust design, so my
question is does a similar thing exist for carburetion? or do we have a
real carb guru in the group?

It is a 36mm Amal Mk2 smoothbore.

TIA

 

If you can afford to throw a couple of hundred quid at it, going the
dyno route will leave you with some hair on your head & skin on your
knuckles. A *good* dyno operator will probably know which main jet to
go for after just one run, & get pretty close with the needle. Getting
the mid-range spot on could be nigh on impossible if the needle taper's
completely wrong, but that seems unlikely.

Dynotech near Basingstoke worked wonders on my Tiger. PDQ also come
highly recommended, & apparantly do quite a few MX/Enduro bikes so
should know their 4-stoke singles. Maybe not much use if you're oop
North though.

 

North? nah! Milton Keynes area, I guess yell.com is my friend, however I
do prefer to work on reccomendations.

 

http://www.dynojet.co.uk/dyno_centres.html could be your best friend -
Dynotech & PDQ are both on there. I believe Dynotech have done stuff on
the Team UKRM bike in the past, so maybe Champ or someone will be along
in a while with an opinion.

They mapped the Power commander on my MV earlier this year too, so you
can definitely take that as a recommendation - I'm very fussy about who
I let near that!

 

Good point, and there is a local one, I will call them it will probably
save me hours of hassle.

 

Yeah - Dynotech are good.

Also, I've heard very good things about Cambridge Motorcycles.