Jetting specs GT750 vm34s

[re5rotary]

Hi can anyone help with some baseline jetting specs for a GT750 ported barrels, spacer plate, chambers etc using VM34 carbs? Ive done a search and there is the odd mention of jets on the Bimoto GT thread but I wondered what jetting he ended up with when he got it running properly? regards Terry

[tz375]

Start with 159, P-8 Needle jet, 45 pilot jet, 280 hex main jet and 6DP5-3 needle. That's what I know worked for someone with a similar build. He endd up with smaller mains and pilots, but start rich and work down. If you use #188 needle jets which are identical but take round main jets, you would use say a 130 round main jet and work down.

What did they come off and what jets are in there now?

The needle and needle jet are critical for nice street riding. We rarely get up on the main jets on the street but it's good to be rich there.

[re5rotary]

I was looking to buy new VM34s the first number you state 159 what is that please?

[tz375]

Needle jest come in a variety of sizes to suit different carbs. VM34 usually have #159 series needle jets. Some OEM carbs take needle jets that are dimensionaly identical to the 159 series but are threaded for different type of main jet. Round main jets are numbered according to their diameter where Hex jets are rated by flow rates. 200 hex main jet flows twice as much fuel as a 100. With round jets, 100 means 1.0mm and 200 would be 2.0mm diameter so it would flow approximately 4 times as much fuel as a 100 round. So it is important to know what series/type of needle jets and main jets are used when looking at jet numbers (sizes)

[A.Holley]

Don’t know if this helps at all, but I run VM 34s on my T500
Running chambers, pods and decent port job plus reed valves
I ended up with 260 mains(hex type), P2 needle jet, 6DH3 needle ( 2nd from top groove)
35 pilot jet and No1 cutaway slide
Fuelling is clean from udlecall the way through now