starbiscuit
Well-known member
I have given up for now on the 30 pict 3 that was on my 1970 bus.
The local "bus whisperer" said it was un-tunable, that it needs a clean and rebuild to unblock the passages and stop the spindle air leaks.
So I bought a Brosol H30/31 from GSF as a stop-gap on a 35% off weekend.
I have read much here and on the interweb, with opinions both ways on the quality of this carb and what its jets should be.
Given that this is the *only* replacement carburettor listed by GSF for *all* VW air-cooled, it seems a bit of a stretch that it could work out-of-the-box for everyone. However, I'm told that it is somehow optimised for SP engines with single-vac distributor. With conflicting advice that they ship jetted for (a)1500 or (b)1600. Whatever that means in numbers.
As I understand it, with like for like engine-spec, a bug will have a richer main jet than a bus. Don't know why, but it was a pearl I read somewhere.
And that DP needs a richer main than SP, and that 009 dizzy needs a richer main to mask the flat spot.
And there's lots of discussion about which physically is the IDLE jet and which the POWER jet.
Anyway, my carb shipped with 130 main, 50 in the right-hand straight jet and 65 in the right-hand angled jet.
And there's a 120 main spare in the box.
I have a completely stock 1600sp with OE vac-only distributor. 205M I think.
Not wishing to ruin anything whilst trying to determine what is the best jetting long-term, which do I start with: 120 or 130 main?
Lots of folk say 120 is too lean for a bus, but it's not clear to me whether that's true of a stock vac-only SP, or just an 009 DP, or with bigger bore, or hotter cam, or better exhaust.
130 to 120 is two whole steps leaner, so I'll be coking plugs or cooking the valves, if "the other one" was better.
Any thoughts?
Thanks for reading.
The local "bus whisperer" said it was un-tunable, that it needs a clean and rebuild to unblock the passages and stop the spindle air leaks.
So I bought a Brosol H30/31 from GSF as a stop-gap on a 35% off weekend.
I have read much here and on the interweb, with opinions both ways on the quality of this carb and what its jets should be.
Given that this is the *only* replacement carburettor listed by GSF for *all* VW air-cooled, it seems a bit of a stretch that it could work out-of-the-box for everyone. However, I'm told that it is somehow optimised for SP engines with single-vac distributor. With conflicting advice that they ship jetted for (a)1500 or (b)1600. Whatever that means in numbers.
As I understand it, with like for like engine-spec, a bug will have a richer main jet than a bus. Don't know why, but it was a pearl I read somewhere.
And that DP needs a richer main than SP, and that 009 dizzy needs a richer main to mask the flat spot.
And there's lots of discussion about which physically is the IDLE jet and which the POWER jet.
Anyway, my carb shipped with 130 main, 50 in the right-hand straight jet and 65 in the right-hand angled jet.
And there's a 120 main spare in the box.
I have a completely stock 1600sp with OE vac-only distributor. 205M I think.
Not wishing to ruin anything whilst trying to determine what is the best jetting long-term, which do I start with: 120 or 130 main?
Lots of folk say 120 is too lean for a bus, but it's not clear to me whether that's true of a stock vac-only SP, or just an 009 DP, or with bigger bore, or hotter cam, or better exhaust.
130 to 120 is two whole steps leaner, so I'll be coking plugs or cooking the valves, if "the other one" was better.
Any thoughts?
Thanks for reading.
