VHSH30 Baseline Settings:Rok Shifter

Trying get a “baseline” setting with my carv, a Dellorto VHSH30 w/ Dellorto fuel pump. A lot of web scouring makes me believe all karting roads lead to KP, because I found this:

Per the settings as mentioned by Christian Fox, (post 5), would that be a good baseline overall or just for Rotax?

Rok shifter just put in the jetting allowed by the rules. Though there’s some selection of inner pilots.
I usually run a B45 inner pilot. Main jet will depend on what your air is like, but start with a 155 and jet down as required.

Like Ricky posted, the tuning setup is basically laid out for you. If you’re competing with it, these are the rules you’ll follow.

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I should have clarified, regarding the idle and air screws, is there a baseline to start from, i.e. idle, 2 full turns out from closed, etc?

Example: i can’t start it on the stand by myself unless I have a 2nd person to pull the throttle cable a bit. My thought was to start with air/idle first, but was looking for a baseline.

choke on? That would be my first go to if it’s cold.

I use the vortex engine app to track my carb set ups. its not the most accurate thing in the world because there isn’t a rok shifter option. However, its great if you want to just track your carb set ups or compare different ones.

Now with that being said, your baseline settings all depend on your elevation. I’ll use new castle as an example. The track is around 1070’ in elevation. My air screw baseline for there is around 1.5 turns out. I’ll adjust based on humidity, or how it revs. Sometimes it requires some fine tuning while revving. Again, this is all dependent on your location and the weather that day.

For the idle screw, adjust it all the way in so that the kart idles itself, then back it out until it just barely dies, then i’d leave it alone. If it starts sputtering when you go to shut it down, back it out a little more to stop that.

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Thank you! I’m between sea level and 300’ above, so low elevation. I tried the Vortex app, but when it showed no option for the shifter, I was a little wary.

Yep, choke is on to stary, and it actually idles better hot than cold (choke off, of course).

that is perfectly normal. Engine should not idle. If you are alone, wrap a strap around the wheel and pull from the front of the kart, so the kart won’t move forward as you are leaning on the bumper. The other hand can pull the throttle cable or pedal. Start in 2nd if you are having trouble with too much compression

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Thanks, Andy. Going to have to work on my core!

I would definitely reference the photo Ricky posted as far as getting a baseline setup for that carb.

Our jetting is going to differ greatly just because where I’m at is different than you by a lot.

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Maybe someone can explain this to me, but don’t understand this (what seems to be recent) trend towards tuning in a way that doesn’t support idling. In some cases (like a DD 100cc) it’s not practical to have a setup that idles, but those karts more-or-less don’t exist anymore.

However with a KZ (and by extension Rok Shifter) I really don’t see the benefit (especially for recreational karters) of forgoing idle engine. The carb is well suited to it and the engines are certainly capable of it.

Yes, technically they can sustain idle no problem, like you said the dellorto is well suited for that. In my opinion there are 2 benefits, one is safety the other performance.

Safety: let’s say you turn the screw in so it idles on the stand. The #1 reason you’d do that is because you think you can leave the engine running in neutral, so you can lower the kart and then hop in so you don’t need any push. As you tilt the kart, you’ll realize the idle is very sensitive to flow height in the bowl so any tilt will make it die. So logically, you turn the screw in so it idles higher and won’t die when you put it down. It takes a small bump or graze of the shift linkage while on the ground to get it in gear and have a runaway kart…no fun (I’ve seen it first hand from somebody using this approach in combination with an electric stand)

Performance: getting the valve fully closed helps with sending the strongest vacuum signal upon opening, helping with performance at low revs.

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How dare you! :rage:

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Facts are facts on the 100’s. We can’t even get a grid of 100’s together in the US…. Yet. I’d like to think someday we’ll be able to get a good group to meet at NCMP’s annual vintage event. Or perhaps rock island?

I still have my VR98 and TSV95 patiently waiting.

On the idle, I get what you’re saying on safety but I really thats an outlier. Anecdotally I’ve never experienced or witness that. Not saying it doesn’t happen. Juts added my anecdote.

For performance, like I said for someone getting started I recon have them tune for idle. Performance can come later.

Tuning for idle means finding an idle that is acceptable, tune the air screw until RPMs are stable then re-adjust idle? Like you would for a motorcycle?