I'm putting a new Mini Rok on my sons kart. The instruction manual is pretty crap. I have a couple of questions:
- What needle setting (in the carby) do you use? (i.e. Top of the needle - notch 1, or bottom of the needle - notch 4)
- Does the needle setting differ from when you're running in an engine, or racing?
- What "Idle screw" setting do you use?
I'm using a 97 Jet.
Thanks in advance.
Comments9
Std needle setting is 2nd from top, brass idle screw is 1 turn out and idle speed 31/2- 4 turns out. This will give you a good baseline but tuning a mini rok is very much weather dependant just like a rotax with jets, needle height and also float height to consider.
As for changing needle height to run in ..never bothered and also make sure fuel is filtered with a good fuel filter and carby is serviced/ cleaned on a regular basis as they dislike any debris in them They also get hard to start if you tip kart up on stand to unload so try and lift off wherever possible and don't idle kart too much as it wets air filter making starting hard as well. Depending on engine builder used , oils brand and ratio will vary so best to go with what they know works.
Thanks Paul.
The "Idle speed" screw is on the outside of the carby, (facing the side pod)
What is the "Brass idle screw"? Where is it?
https://www.youtube.com/watch?v=uzEtAIzG5jk&list=PLFKUhSKaVS29p...
Watch this, it should help you. Idle speed is one with compression spring on it and brass mixture screw is next to it.
There are several variables.
Restricted or unrestricted?
Float height?
Air temp?
Humidity?
Altitude?
Fuel return line yes/no if yes, what size restrictor?
Unrestricted (Cadet 12)
Float height? As it came out of the box
Air temp? ~19c
Humidity? No idea
Altitude? Oakleigh, so pretty close to sea level
Fuel return line yes/no if yes, what size restrictor? Yes, restictor is a spark plug screw cap shoved in the return line Morgan Jones said:
There are several variables.
Restricted or unrestricted?
Float height?
Air temp?
Humidity?
Altitude?
Fuel return line yes/no if yes, what size restrictor?
awesome video. In the comments , the guy in the video wrote "I start at 3/4, 97maim jet and clip 4 on the needle for sea level tracks. As you increase your height above sea level you can lean the main jet out to a 95."
WTF ... Clip 4??? Paul Knowles said:
https://www.youtube.com/watch?v=uzEtAIzG5jk&list=PLFKUhSKaVS29p...
Watch this, it should help you. Idle speed is one with compression spring on it and brass mixture screw is next to it.
And the beginers to the sport have to put up with this... David Gibcus said:
awesome video. In the comments , the guy in the video wrote "I start at 3/4, 97maim jet and clip 4 on the needle for sea level tracks. As you increase your height above sea level you can lean the main jet out to a 95."
WTF ... Clip 4??? Paul Knowles said:
https://www.youtube.com/watch?v=uzEtAIzG5jk&list=PLFKUhSKaVS29p...
Watch this, it should help you. Idle speed is one with compression spring on it and brass mixture screw is next to it.
Yep.... you need a Phd. to work out these carbys.
I raced Yamaha KT100s and X30 for 15 years before retiring to allow my son to start racing. I feel for the parents entering the sport with no experience at all. David Kerwood said:
And the beginers to the sport have to put up with this... David Gibcus said:
awesome video. In the comments , the guy in the video wrote "I start at 3/4, 97maim jet and clip 4 on the needle for sea level tracks. As you increase your height above sea level you can lean the main jet out to a 95."
WTF ... Clip 4??? Paul Knowles said:
https://www.youtube.com/watch?v=uzEtAIzG5jk&list=PLFKUhSKaVS29p...
Watch this, it should help you. Idle speed is one with compression spring on it and brass mixture screw is next to it.
The carbs are not difficult, you just need to learn what is required and what not. Try this article on how to set the main jet , its a lot easier than teaching the driver to play with adjustable jets as most do not get it until they are 12 or 13 years old, and you will know its correct when the kart leaves the grid and that's one less thing on your mind ............ http://dtec.net.au/Air%20Density%20&%20Tuning.htm
There is clean petrol running thru the carb the whole time the engine is running, so you do not need to strip it every day to clean it, leave it alone. The float level is an important setting, but it is a simple thing to set, do it once and again leave it alone.
The needle clip position is not a tuning aid, it is way too coarse to be used for little adjustments AND it affects the engine tune in the 2,000 to 5,000 rpm range which the Miniroks do not go down to on any of our tracks once they leave the grid. Simplest way to find the best spot for your driver is to get him or her to do 10 laps on each clip position, then ask them which they preferred. Not by laptimes you have taken but by how they felt it. Then go to that position and leave it there. After that you may want to try the same test in 6 months time, once your driver has changed driving habits , or added weight or even learnt to drive more consistently.