Mini ROK won’t idle! Help

Been racing karts over many years and I’m a mechanic by trade…carbs and tuning are my specialty…in the automotive world…but I’m new to the Mini ROK. I have it on a Benik chassis for my nine year old to start racing in Micro…it has the restricted exhaust header.

I bought the engine from a friend at our home track who just had Woltjer do an upper end rebuild and dyno. It had zero time on it when I got it since the refresh.

The engine starts easily and runs great out on the track, but it won’t idle more than a few seconds before just dying out.

It runs the best at idle with the brass idle screw almost all the way in.(1/8 turn out at the most) and the silver, idle speed screw almost all the way in! I believe the brass screw is set at a lean condition so I back it out to one full turn and have him run it. We have about hour run time on it so far with no improvement.

We have an exhaust gas temperature reading of, on average of 1065 high end and 750 low….rpm’s reach right at 13,000 maxed out. I have a large assortment of jets, needles, air bleed and tube so can probably change anything out……
Any suggestions???

If the idle screw is an air screw I would suspect an air leak somewhere since you’ve had to almost stop all air passing by it.

Did the carb come back from woltjer on the engine, or was it shipped without it.

Racing 2-strokes shouldn’t idle…whether it’s a kart or motocross bike…and especially a piston port engine like a Mini Rok. You’re fine.

Thanks for your reply…that’s the most common answer I’ve gotten.

So, no, the carb did not come from Wolkjer, it came separately from the original owner. To be on the safe side I bought a brand new in the box carb and started off with that. When I had the idle dying out problem I switched to the original after cleaning and resetting all the settings. The problem was exactly the same. The original owner said they never had a reliable idle and just lived with it as part of a racing 2 cycle.
It’s only a pain when coming into the pits and driving back to the garage.
A few people have said it’s very common.

Just doesn’t feel right….

Thanks for the reply!