I’m likely buying a Rok Shifter for this season and have found little information on what carb changes are needed from Rok Cup requirements to safely maximize performance for Road Racing. Of course, the main jet needs to increase, but what about the slide, needle, emulsion tube and other jets? Looking for feedback from road racing a stock engine.
Thanks
Hi Bob
Good to see you on this forum. Good luck with the upcoming season. I’m sure you’re familiar with the base TM settings for road racing, but below is starting guidance (as in, don’t blow up) for anyone running stock with a 30 mm Dellorto here in Australia. Yes, I know you’re looking to run a ROK - can’t help you there.
Tom
Main Jet - 165
Needle - K96 (top or 2nd clip)
Tube - DQ269
Pilot Air Screw - 1.5 turns out
Ignition - 1.1 - 1.2mm btdc (Standard ignition box)
Fuel - Elf race102 mixed at 25:1 with Maxima Castor
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@jsipplracing and I are going to be testing this with his Rok Shifter, as he’s got plans to take it road racing this season. With the stock pipe and stock head configuration, the Rok always runs pretty safely even when on the lean side. Jake has a KZ pipe that we will test, and we expect that to help shift the power band upwards.
As far as jetting goes, needle is the first thing I would change. We will probably test in small increments, going to K28 and then to K23 or K27 depending on results. I could see Tom’s suggestion of K96 working well with the KZ pipe. Slide is already very rich, but richer pilot combo could be needed for road racing.
In short, no clear answer from me, but hopefully more insights after we do some testing this spring. There are some pretty major differences with the Rok port configuration vs a traditional KZ, so that may end up being a limiting factor.
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Evan said it pretty well. I am planning on road racing this year with Dart Kart Club. I bought the Vortex KZ pipe (which you can get from fastech or mondokart. I believe its the RKZ pipe). I believe that pipe is going to get me some more power on the big end.
I know nothing about needle tuning, so Evan will be a big help there. I’m going to follow this thread because I was going to start one similar lol. We will definitely have more insights after testing this spring.
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Thanks for the feedback.
BTW - I’m hearing AKRA will require Rok Shifters to run a stock pipe, airbox, cylinder and head against Hondas in the new class. Basically Rok Cup rules other than inside the carb.
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Oh… thats news to me. Is there documentation to support this? Maybe ill have to run in the KZ class then.
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I expect AKRA / DART with be posting their 2025 Class rules very soon. Then we will know if the rumors are accurate.
Alright. I wanted to update this thread.
First, regarding the KZ pipe, there is a noticeable upshift in power band. I did a direct comparison test with 1 session on the rok pipe, and 1 session on the KZ pipe before the rain came. I kept the jetting the same between the two pipes to try and have some sort of consistency in the test. Carb is still set up for sprint racing but is as follows:
Main Jet: 155
Needle: K98 2nd clip
Emultion Tube: DQ268 (spec rok shifter)
Inner Pilot: B50
Outer Pilot: 50
Air Screw: 1.5 turns out
I wanted to link this thread here because this topic was talked about before.
I think its also worth noting that it’s said you can run stock jetting with increased main jet with the stock rok pipe in road racing and be fine. EGTs in 1250s.
As far as jetting with the KZ pipe goes, I’ll know more after next weekend when I go to Grattan and have the engine set up with the right ignition timing and hopefully the right carb setup. After talking with my local kart shop (PKT), who also specialize in road racing, they told me I need to go richer. But the question is how much richer? We didnt really know as they race Modenas. I’m kind of unsure as to what to order for pilot jets inner and outer (and needles for that matter) to sort of give me a baseline. Hopefully I can get that figured out before next weekend and get the parts in.
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When I had an unknown package on road racing I’d go up ten points on the main assuming the air is similar from the day I had been running the sprint track. This usually put me on the rich side.
You’ll probably be able to get some pointers on the day at the track too.
If you are planning on running the Stock Shifter class against the Hondas you have to use the stock pipe. If you want to run the KZ pipe then you have to run against the KZs in Shifter 125 and you don’t have a chance. I put the KZ pipe on for sunday against the KZs at Summit National last year and it did better, allowed for more overrev in the draft, but you can’t hang on to those guys with that much HP difference. I ran the first 2025 WKC event on the Jefferson Circuit in Stock Shifter with the stock pipe and its a good pairing against the Hondas…
Well damn. Guess i will be using the stock pipe and airbox since thats what theyre requiring. Im having a hard time believing that theyre gonna mandate the carb rule just because road racing.