need a little help in jetting my bike carbs, taking off the float bowls i think im right when i assume the largest screw in the middle of the float chamber is the main jet and its this that needs drilling out.

cheers

james

redrill to 1.6-1.7mm

I am using 1.6mm drilled jets on my Mikuni BSR34 carbs pinto running , works great. I suppose if you are using larger carbs 36mm+ I would go for 1.7mm just to prevent the greater flow from running lean.

The drill cost me a few quid tho.. might be worth checking drills at model shops, they might have 0.1mm increments..

tak

Rolson do some small indexed drill sets that go up to 1.6mm. I use them in a dremmel type drill. They were from the flea market tool stall and only cost a few quid. Some here on ebay but mine were cheaper.

[Edited on 17/10/06 by Peteff]

i have the drill but im just unsure of what i need to drill and am afraid of screwing up.

i have uploaded a pic to my archive named bike carbs i think i need to drill the large screw in the middle of the 3 together with a hex head below it...am i right?

cheers

james

New jets are only a couple of quid each! A 160 Mikuni jet is 1.6mm, a 170 1.7mm etc....

Believe this if you will - my 250cc v-twin Grand Prix bike came with 560 main jets! That's 5.6mm on a 125cc cylinder!!!!
I now run around 400's, which is still obviously 4mm!

I use 175's in my mikuni carbs on a 1.6 pinto. Yes the bit you are reffering to IS the main jet. Just wait till you get onto setting the needle height etc....thats where the fun begins! Oli.

pray tell then oli how do i go abouts setting the needle height?

take the top off the carb..

The needle height is set by a tiny circlip and spacers in 1 of 4 grooves at the top of the needle - and hence adjust the height it sits at... you take off the top of the carb -beware that it is which is under spring pressure.. once off, you can lift out the diaphragm and slide choke mechanism.. the needle is mounted in the slide

the needle is held in place with a push in/pull out friction clip, and is easily plucked out with needle nose pliers and just as easily pushed back in.... the rest should be very obvious, with regard to adjusting the height. I would only move it 1 groove at a time, and see how it performs..

atb

tak

Is the main jet the only jet that needs drilling?,if so I assume its a combination of that the needle height and mixture screw, is that right.