srx 600 carb max choke size

[shaggy]

hi

I have been offered a mikuni bst 40 carb from a friend to fit on to my srx 600 which is going to be bored out to 640cc

Is a 40mm dia. choke carb too large for this engine? I know these are fitted to ktm 640s but obviously they are two very different lumps ?? thanks

[Steve H]

40mm choke = 1256 mm squared
Pair of Keihin CR33's = 1710mm squared
Not sure of the stock carb sizes, but the total area may be close to the 40mm choke.

So in terms of size it isnt too big, whether its has an effect on throttle response/ bottom end I cant say. I beleive SteveL and several others have used single carbs they may be able to add more detail.

[Steve Lake]

Yes indeed, i ran a 42mm Dellorto (with accelerator pump) on a handmade two into one manifold.....and it worked very well, on my #1 srx6...which at the time was 620 cc....only reason i'm not using it now is because i won a pair of 34 mm dellorto's on ebay and thought i'd give them a try for a year.
lots of things you need to be aware of when going down this route.....
Obviously you will need a one into two manifold.....as short as possible
the height of the dellorto required that the tap assembly on the tank had to be removed (the hole plated over) and the tank area immediately above the carb had to be bashed in with a leather mallet to allow sufficient clearance.
new petrol feed outlets need welding into the tank (mine are either side at the lowest ends of the tank)
if you use the standard fuel tap, then you will need to run the tap on 'prime' unless your carb or manifold has a vacuum take off.

the breather on the top of the oil tank had to be moved to one side, and your throttle and choke cables need modifying

your throttle and choke cables will need modifying to match the carb (single throttle cable)
probably other things i've forgotten....but thats enough to be going on with :-)