Need help on go kart

[bob geo kart]

So I'm new to go karting and stuff. I can do engine work and stuff but can't weld or fab. I do have a friend that can weld. Anyways, I have a cater bros mini talon frame that I'm extending to fit me. I'm gonna put a 6.5 hp (196cc Lifan grey hound) with tav 2 TC on it with some mods to the frame because the frame had a lawn mower engine on it. The engine was used kind of hard and the engine sleeve was rusty from an open valve but me and my friend got it to run. I did lose the throttle linkage and we threw away the gas tank. So I want to put a mikuni carb kit on it with a lawn mower exhaust (from a 400cc Briggs so it is big enough) and a .10 head gasket. I want it reliable but also to rev high. I was reading that stock valve springs go about 5200 rpm which it fine for me but is it safe to have valve float like that. A friend has 18lb valve springs that I could use.
So can I do this without any thing else, what rpm am I looking at and what HP.

Now the drivetrain, I'm gonna use a 1in live axle with a 60t sprocket and a 10t on the TC. I want the thing to be an off road kart. I'm using a 7x 5 3/4 rim with Carlisle Knobby ATV Tire - 16X8-7 and the fronts are 4.10-6 hole shots.. Would this be a good ratio for the engine and would I get good traction and handling.

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[madprofessor]

If I say nothing else hear this............Never increase ungoverned rpm's by putting in stiffer valve springs to prevent valve float unless any cast iron flywheel has been upgraded to a billet flywheel.
No idea what "lawnmower" engine you're talking about, but are you going to use it or put in the Lifan? You're being confusing there.
If the mods you're talking about were a Predator 212, or clone, or Honda 200, etc., (don't know the Lifans) then the cast iron is definitely the stock flywheel. It can literally explode at high enough rpm's, and the grenade pieces at that speed can pass thru motor housings and human flesh like crap thru a goose.

 

[bob geo kart]

So if I keep stock springs ill be good? Also the exhaust came from a briggs flathead 400cc. I'm gonna put that exhaust on the lifan 196cc(it's a honda clone) for higher air flow(I cut off the muffler so its a straight pipe). It doesn't matter how fast it revs to me I just don't want it to break and explode like you said.

 

[Denny]

With higher rpm you also will have to upgrade to a billet today or the rod will pass through the block like crap through a goose.

 

[Denny]

I hate spell check! Was supposed to say billet rod.

 

[bob geo kart]

Ok. So billet rod and flywheel thats about 160 to 200 bucks and I don't have the money for that. So do I need that if I use stock valve springs? Or should I just wait and save up and get 22lb springs,cam and billet rod and flywheel. The reason is I dont want to upgrade is because I'm spending about for 400 dollars on the kart and it's just a off road kart so doesn't need to rev high.

 

[madprofessor]

Not quite so much. I didn't buy from OMB, but a quick look at their site shows a billet PVL flywheel and a billet ARC rod for $65 each plus shipping.
Denny is absolutely right that not only a billet flywheel but also a billet connecting rod are necessary when using heavier than stock valve springs to increase rpm's.
The rod's just less critical than the flywheel because when you throw a rod, it usually only destroys the motor without coming thru the block at 200 mph. and on thru your skull.
Rod's more critical than the flywheel on a STOCK motor because a stock rod is inherently prone to break at any time for any reason. Just imagine it in a hotrodded motor. The little splash arm that sticks out at the bottom of the rod to splash oil around in the crankcase and up the pushrods passages is the part that usually breaks off, and soon as it does you lunch the motor.
So replace the rod no matter what else you do, and replace the flywheel if going to stiffer valve springs.
NOTE: A .020" over-length ARC billet rod costs the same as a stock length rod, gives you noticeably more power via more compression. Since you should pull the head to replace it, the .010" head gasket you mentioned does the same thing from the other direction. I recommend both.
Don't worry about a modified cam, you'd likely have to pull your crankshaft and do some grinding on it for cam clearance.

 

[bob geo kart]

ok. i think im just gonna use stock springs, maybe later ill upgrade it. Anyways thanks for your help guys .