C51 Kid Kart racing - WHy is my kid's engine so much slower?


TRUMP 2020
Step 1 = blueprinting does help.
Step 2 = cranking compression pressure is important, check it often. A "good" compression gauge is not cheap, buy a good one.
Step 3 = check to see if the clutch is holding the engine at peak torque on the starts. Really important!!
Step 4 = exhaust gas temperature gauge (EGT) is a "real" tuning helper.
Two karts, side-by-side, going straight, hit the gas at the same time and, one pulls away from the other, can mean several things.
Two of the most obvious are, lack of horse power and/or poor clutch performance. If there's no "gearing" rule, I'd be looking at that too!
You might think that paying to get your engine tested on a dyno is expensive, but, just starting out and testing at the track for all the things you need to test for can be expensive too!
Tuning is tough" (Al Nunley)
Good to see you ole man, you on the lamb?

alvin l nunley

Premium User
Step 3 = check to see if the clutch is holding the engine at peak torque on the starts. Really important!!
In answer to your question: having your clutch holding your engine that peak torque is real important. If your engine is holding your engine at peak torque, that torque is transferred to the rear axle through the chain, with peak torque at the axle, you have peak HP at the axle. Really simple. The formula for horse power is; torque X RPM/5252.1 = HP. If you transfer peak torque to the axle, you have peak horsepower at the axle, of course that is when the clutch is slipping, when it locks up, the HP is the same at the engine and the axle.
Put a bathroom scale between the front of your kart and a strong wall. With the driver sitting in the kart, start the engine, warm it up a little, stand on it, read the RPM and the scale very quickly. It only takes two or three seconds. Adjust the clutch to hold the engine at a different RPM. Do the test again. Find the RPM where you get the highest reading on the scale. That's where you're getting the most HP to the ground.


9800 is a poorly running engine for certain. 10,500 should be very easily attainable from any blueprinted engine. Good ones will run 11k plus as well. The start advantage was likely an outlaw clutch they slips a lot higher.

Kid kart is the worst class in karting for this simple reason.... instead of simply working on driving here we are talking about engines. So frustrating


More than likely you up against some questionable engines. We noticed at our track when tech guy was off that weekend we almost got lapped. When he was there we would finish on same straight away. When we graduated to full size one of our competitors did too. I noticed on here he started selling comer outlaw parts for a friend. Ya right. To run with big boys you got to change piston ring often, check tow, and get axle to spin forever(reduce rolling resistance) , make sure you muffler isnt carboned up using castor oil. Took me two weekends to figure that one out. Take torch heat it up and it will burn out on it's own. Make sure choke is completely off. Burnt twice by this and on and on. Best day of my life when we quit running a comer.

So much false info and truth to this.

1. The worst thing you can do is change the piston ring. If you have solid compression leave it. Don't touch it.
2. Check toe, get your axle spinning freely on a very low hp class? Yes.
3. What are outlaw parts? Clutches. Some areas they are legal. Unless you are a running at a track where it is a standing start they don't help. I had outlaw parts for sale. Carbs that came with engines that were drilled out and messed with. Never ran them. Won a lot of races. It can be a frustrating class. If you have a kid that wants to win you have to put some work into it but it isn't hard. If you want to pull a rope and be done with it honda is a great class too. I prefer the challenge.


1. Keep your carb clean
2. Learn what jetting does (buy a pin gauge set and a jet block and label them from .230-.259
Air density learn which jet does what. When you get the motor and driver dialed in 90% of the time you are on one jet.
3. If your kid is newer buy the cheapest engines out there. You see one for 300 bucks pick it up. When he\she is getting better you may have 5 engines for $1500 total. Pick the best two or three and get them done by an engine builder.
4. People will be glad to help you. Don't be afraid to ask.
5. Don't blame fast kids on cheating. Chances are the engines are legal. We ran fast and I 100% guarantee you it would pass a CC tech even for club races. The guys making a fuss about it probably could not say the same.


We have the same thing at the track we race, there's 1 kid who is 2 seconds a lap faster than anyone else and almost 3 mph faster through the speed trap. We are meant to abide by WKA rules but for the kid karts, they never check apart from safety items. His kart is prepared by a local race shop and good for him, he's an impeccable driver very consistent and never makes a mistake. Us Dads have talked about how far we could go with blueprinting/skirting the rules if we wanted to spend the money but 2nd-8th usually finish within a few seconds of each other and the racing they have is just awesome to watch. You never know who's going to finish on the podium, sometimes they are 6 wide going into turn 1 and when they come through the final turn they are still 6 wide. They have a blast and learn so much from wheel to wheel racing that will help them when they move up than they would if they ran off into the distance with a better engine. #1 goes back to his motorhome while the rest of the 4-6 year olds standing in a circle in their race gear tell wheel bumping stories & see who has the most paint exchanged on their kart with high fives & fist-bumps. Seeing that is my favorite part.


Dawg 89
sounds to me you got the best of it .
I wouldn't change a thing .
Plan on spending 1000 or 2000 dollars on the engine .
Of course carb and exhaust is avalible .
Its all laid out in this thread .