VM Mikuni Needles.

[suzuki27]

Does anyone know what the number  4 in needle size 6HD4 ,refers to. I can't recall if it is the taper or diameter or what. I need to get hold of a 6HD3 for a VM34 Mikuni and it came with the 6HD4. I am tossing up whether to try it. Would the 6HD4 be leaner or richer than the 6HD3?

[vandy010]

are you sure you've got the 'D' and the 'H' around the right way?
as i can give specs for the 6DH3 & 6DH4

[suzuki27]

Oops. Yep I did have it arse about. Those specs would be helpful Vandy.

[vandy010]

thickest is lean, thinest is rich.
straight from the mikuni catalogue,
hope this helps.

[suzuki27]

Thanks Vandy. So the DH4 is thinner than the DH3 and a bit richer.

[vandy010]

So the DH4 is thinner than the DH3 and a bit richer.

thats pretty much how i read it.
with the '4' being slightly leaner at idle.
me personally, i'd run the needle you have and after a few rides/plug checks etc make the decision from there.

[suzuki27]

I will try the DH4. I have gone to a 34mm carby on an RM125-standard is 32mm. The specs I got from an old US Dirt Bike were for the standard carb after it had been bored out to 35mm. I cannot see 3mm of spare metal to remove from the 32mm. I will try the 34mm first and might think about getting 1mm bored out of it down the track. I have a bigger fuel tap etc to increase flow. Keen to see what difference it makes. I will let you know. Cheers.