Hi everyone, recently I bought a KT100S go kart. It ran fine when I bought it however does not work when I bring it back home. I adjusted the high speed and low speed adjustments and fiddled with the idle screw on the carb, but it turns out that the carb was perfectly tuned before messing it up. My neighbours confirmed it as being a fouled spark plug and we replaced it. However, I also put in the wrong fuel/oil ratio and the carb was still messed up. It starts on the stand and when pushed. But it isn't able to take throttle when I sit inside of it. It does take throttle when on the stand though. Anyone have any settings for the carb on the KT100S and a good fuel oil ratio? Cheers!
KT100S not taking throttle?
- Thread starter Lil Stig
- Start date
Rat
Well-known member
Double check the fuel tank with a good flashlight, make sure theres no silt. I worked on a LE-150 Hammerhead that has a steel tank that had done exactly as you described... ran great in the showroom, didn't run off the trailer. Turned out that for some reason it had a layer of steel dust that was plugging the filter and some of which was fine enough to get far enough to plug up the carb.
No one can give you an answer to "best jetting" or "best settings" for any carb. The reason is there are too many variables among them being altitude and ambient temps.
The baseline default for any carb is to soft seat the pilot circuit adjustment screw and back it out 2 full turns, then soft seat the idle screw and back it out 3 turns. You'll need to get it ran up to operating temp before you adjust anything after default.
As for the pilot screw you want to turn it until the rpms stop climbing, with the idle screw default this should have it well above idle. Once you have found the point it stops climbing, back it up a 1/4 turn and proceed to let the idle screw out until you find the lowest possible idle it will hold without stumbling and you should be good to go unless there is some other underlying issue.
I recommend checking torque on all bolts, a new engine and a freshly overhauled rebuilt one tends to compress gaskets after heat cycling which "loosens" the the bolts... they generally are at full seat after 3 ir 4 heat cycles.
It should start from there at which point tuning can begin. As far as spark plugs go, NGK BR9EIX Iridium plug is the most recommended.
As far as premix ratio Never more that 40:1, but 50:1 of a high rated premix will burn cleaner, foul less often, and only billow massive clouds under heavy throttle or loads... but still more than effectively lubricate.
Rat
Well-known member
First of all there's no indication on your profile if you're in the states or otherwise. Anything being said in another country is completely irrelevant to me because A. I've done the research, and B. I have the practical experience wwhich parallels with the research.
From what I've come to understand over the years is that "2 cycle oil" is not a globally available product.
When you see obnoxiously oil heavy ratios recommended (litteraly anything greater than 40:1) it is from a region that in fact does NOT have 2 cycle oil thusly the ratio is for 30w motor oil being used.
ALL modern 2cycle premix oils are of a quality level allowing them a maximum ratio of 35:1 with the ideal ratio being 40:1, Premium 2cycle oils like Amsoil, US-1, and Saber, are best used at a conservative 50:1 or even 55:1.
The fact is that 30w oil is not intended to be burnt in an engine, but will and to get the lubrication done you need a lot of it.
As far as plug fouling goes, 2cycle is known for it because they are dirty engines engines to begin with, but using too much premix oil will kill power and foul a plug faster than being poorly tuned will almost every time.
Even a Cheaper premix like STP Universal 2 stroke oil runs great at 50:1 with no lack of lubrication.
It's only called universal because it is thin enough to put through an injector pump on a 2cycle engine that has a mechanical pump and self mixes based on rpm, marine grade 2cycle oil is a different animal entirely.
A lot of older 2 cycles had pumps and many were ignored in favor of premixing mostly because the oil was just too thick and would not meter correctly or would clog the pump completely; either one leading to engine damage or failure.
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JimD
Well-known member
Just another thought -- Since you just got the kart ask the previous owner what fuel did he race with gas or alcohol? The carb is set up for one or the other. RAT gave you a lot of food for thought and it is all very good. The 18:1 ratio is way off, use that and you will go broke changing spark plugs. Where are you located? What tracks are near you that you plan on taking the kart to? Get rid of all the old gas you already mixed, take off the fuel tank and clean it out until it is dry, blow out the fuel line, and start over with the proper fuel mix and a GOOD 2 cycle oil. The guy that sold you the kart can recommend both the oil to use and the proper ratio.