200 kart engine

I have been involved with engine building and development for all types of racing for almost 50 years. The latest challenge has been small 200 cc kart engines design. You want a tuning challenge try taking a engine that is designed to run at 3600 rpm turn it 8500 every lap and get the fuel curve right with a $15.00 dollar carburetor. The engine is data logged every lap as well as having installed an O2 sensor a few months ago. The #s don’t lie after hundreds of hours in changes and modifications I still cannot get the fuel curve correct at the top of the rpm range. A single cylinder engine does not allow for any imperfections in tuning at all. My point is that I am very interested in how development of this tech for small engine goes. Love to work with if possible.

John C

Welcome, @Shifter!

The sort of standard problem that @TravisNano needs info on for development is generator output at idle. There needs to be some excess capacity to run the fuel pump to pressurize the fuel system while the engine is at idle.

If you can let us know what model engine you have and provide any electrical schematics for it, that’ll be helpful.

The engine is a standard 200 cc Honda and would need an auxiliary power supply to run a fuel pump. Currently I have 6000 mah battery onboard to run the tach and O2 sensor.

Wow, this might open up a can of worms.

Guessing that you have thought about some of these points, but i’ll throw them out there as they come to mind, might help others with similar ideas, or they might have an idea of something that I have gotten wrong.
Being a racing cart you no doubt will want to keep the weight down, and the lack of a charging system adds to the challenge.
I’m assuming that your current battery pack is Li-ion (being lighter, but more $$$), and so will probably need to run a secondary pack, or upgrade the existing.
Currently the total power requirements are unknown, but will need to be calculated considering total run time required and a buffer.
I’m thinking a volt meter that is in easy view, so that you will know when voltage is getting low, and possibly Travis adding a low voltage cut out to avoid over discharge of the battery.
Different voltage levels selectable depending on battery chemistry or personal choice.

Travis loves us giving him more challenges. :+1:
(Secretly I think he does, as it makes for a more evolved package, and better overall.)

I am currently in the process of building a Hilborn style single injector set up to try. The challenge is adjusting the return flow while reading the Lambda #s on tack and trying to keep the kart on an optimal racing line. I would be nice if Aim Sports the manufacture of Mychron 5 data logger I run could incorporate EFI into there system. I am sure at some point they may.

Food for thought

Do you mean one of hillborn’s mechanical fuel injection setups?

I assume here you mean the fuel bleed off pressure?

Sorry i’m a little confused.

If low cost EFI for powersports applications become ubiquitous, i’m sure some dashboard/headunit manufacturers will start including lambda in their systems to make monitoring easier.
Though, on the other hand, custom EFI has been a thing for a long time on automobiles and aside from gadgets and gauges devoted directly to the process of tuning, most other 3rd party systems don’t include the ability to display that information.

I will say, I used to have a VW Jetta from the early 80s that had mechanical fuel injection, and the idea had completely escaped me until just now. You might have a look at the tillotson TCT for your application. Likely to be worlds cheaper than the hillborn solution. Admittedly, it is halfway between a carburetor an EFI system in turns of function.