Main Jet Sizing ??

[Anonymous]

Can anyone help out with approx. main jet size?

I have RS34's Mikuni's on my GS1000, / 1085 wiesco's / 82gsE slightly ported head / 4-1 jardine / 108-109 cam timing / dyna ignition /

There are 125 mains in it now and it runs real well riding around moderately.
I opened it up the other day (after a break in period on the engine) and it pretty much fell on it's face. I suspect it is too lean ... so any thoughts on this...130's? 140's ?

[KEITH KRAUSE]

I'm not familiar with your carbs, but I have a '79 GS1000 with stock carbs (Dynojet kit), 1085 pistons, K&N pods, V&H pipe, 106 cam timing, Dyna S.
My mains are 138 DJ, which are the same size as 130 Mikuni jets. Runs very well. Your 125's sound too small. You did'nt say what filters you run.
If you have K&N's, I would guess 135's ?

[Anonymous]

Thanks Keith,

I am using UNIFILTERS - foam type - with filter oil. The carbs are new Mikuni RS34 smoothbore flatslides. Another point of interest is that the oil temp is a little high after 1/2 hr at highway speed. (I have an "S" model with an oil temp gauge) It was a hair under 300 degrees on a 60 degree day, and then comes down when you slow up. This also tells me lean. The 135's sound like a good start... I was looking to get close from advice so as not to spend a lot on main jets and tickets trying to dial this in.
It's a little difficult around here to hold it wide open for a good plug reading!

Moto

[Billy Ricks]

Moto,

RS36 or RS38 carbs are what your bike actually calls for. With 36's you are supposed to run 130 mains and for the 38's Mikuni calls for 135 mains. What position are needles set on? The Mikuni manual calls for -3 on the 36's and -2 on the 38's. I know these are just starting points, but it is what Mikuni recommends.