VHSH 30 nozzle sizes

Hey y’all. Continuing saga of learning my Dell’Orto VHSH 30 carb. Didn’t realize this until now but apparently there are different nozzle sizes? Mondokart (my usual go-to) has 3.5, 5, 6, 7, and 8, and the description says that the different sizes pertain to the height of their projection in the venturi. Though, I do not know exactly what effect that height would have.

A few questions then:

  1. How does one go about removing and installing one of these nozzles? Doesn’t seem to be a place for a socket to grab, so maybe it’s press-fit? I THOUGHT briefly about trying to grab it with a needle nose and gently turning (or pulling), but thought better of the idea, afraid i was going to bend something and surely there was a proper way to do this that i just couldn’t see. I’d really just like to know what’s in there now, as a starting point. I bought this used and I’m trying to cover off on all the potential unknowns.

  2. This carb feeds an X30 shifter, and I use 260 GTX fuel. Is there a normal size nozzle for this arrangement, or is this a more advanced tuning element and therefore I should just stick with middle of the road unless down the road I want to play with it, etc.? I’ve never seen the nozzle mentioned as part of the carb tuning (just the other 27 parts!), in any of the dozen materials I have on the subject and this carb in particular.

Thanks for any insights!

I’m not a carb guru, but never have I treated the nozzle as a tuning tool, nor have I heard of others doing so. I know that the Rok Spec version of the VHSH 30 (9305) comes with the 7mm nozzle, but I’m not sure what the standard KZ spec (9303) comes with. I’ll be able to measure this weekend and report back. My advice would be to dismiss this as a tuning element, and instead focus on the atomizer and needle (and of course main jet).

I agree on the above, I don’t advise touching it. Is it a tuning element? Of course, I know for a fact that few of the top tuners in Italy actually work on that. Different length and shape have an impact on the depression signal within the venturi. By comparing their carbs with my 9304 I’ve noted few differences. The ones that had such changes used a different emulsioner, main jet and needle combination. That’s next level stuff, I think it messes setups so much that it’s not worth the effort if you are not running an engine tuning business

It’s deinfately an advanced thing. I recall when i was road racing there was a “hot” setup that used a different Etube and needle. The setup was so different that it called for a 128 main instead of the usual 150-160

128 main on a road race circuit would have me in full-pucker mode for 100% of the race just waiting for that thing to :boom:

Yep, that’s what I’m saying. It was Tom Barth’s setup for the TM.

apologies for my ignorance here, who’s Tom Barth? I haven’t spent enough time in US, I searched his name and he comes up in lots of KZ discussions, did he run an engine tuning business?

Yeah he was a tuner based out of Michigan. Mostly road racing. Absolute KZ die hard specialized in TM, did not take kindly to motos and was often outspoken about them.

Loved the guy but I don think he would have liked the KP forums hahaha.

Hey, thanks everyone so much for chiming in, that’s really helpful. I just measured just out of curiosity and it’s 7mm, so not the highest and not the lowest I see available for sale, so I’m guessing that means the former owner didn’t change it from what it came with, and I can safely consider this part an advanced tuning element that is fine as it is, well beyond where I currently am with understanding my kart, and nothing I should worry about at least for now. Appreciate the help nailing one more thing down on my little journey here.

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…enjoy the journey! Jetting is fascinating and really rewarding