Hello and welcome to the forum. We will need a bit more info to help diagnose the problem.
How many miles are on the engine?
What fuel/oil mix are you using?
Have you made any carb adjustments? if yes then please describe.
Do you have "capped" nuts on the cylinder head?
Did you rinse out the gas tank before using?
Is everything else stock from the kit?
Is the clutch working properly?
Approx. 250 miles on engine. Using 24:1. Carb was initially adjusted for rich fuel mixture,not changed. Yes capped nuts. Rinsed gas tank with gas. Cdi unit is not stock (brand new "racing"). Clutch working properly.
The bike worked like a champ until I noticed a strange noise. Magneto loop was loose and vibrating around upon inspection. Tightened it back on and it started right up. Happened again sometime later and got completely destroyed. Replaced cdi and magneto. No spark. New spark plug, cdi, and magnet. No spark. Wired correctly (kill switch completely unhooked but it always worked properly) not sure what the problem is. Can't figure it out. Magnet is positioned correctly based on TDC. Any other questions I can answer to help. Just want my sweet baby to glide me around once again.
Okay, some thoughts then. You can go to 32:1 which is a safe lubrication ratio. The stock capped nuts can top out against the bolt. You can replace these with regular nuts or cut the caps off and re-torque the head. It can be hard to see the spark in daylight. You can try a smaller gap on the spark plug like .024 or .022 to see if that helps at all. Check for continuity on the wiring harness from magneto to the cdi. Check muffler and air filter in case they are clogged up a bit.
With any luck some more experienced members may have more or better ideas.
First things First.
1. Pull the plug, reconnect the plug wire and hold base of plug to motor head - engage clutch (release the lever) spin rear wheel. Do you see it spark?
2. If you do see the spark but the engine will not start - it is possible you have the spinning magnet upside down. Timing 180 off.
3. If you do not see a spark - disconnect the kill switch then check for spark again. I have found a defective kill switch which had driven me insane for about 3 days. I hope you figure it soon.
possible you have a bad ground where mag stator bolts to motor, but 'weak spark' may just mean your gearing doesn't allow you to turn motor fast enough to get a fat spark - is it a coaster brake with only one speed?
that may mean it will take serious pedaling to get it started (might need to go fast & far enough to blow excess fuel out of motor)
I've used external star tooth washers with the lug terminal on my Briggs engine and also kill switch wire. It might oxidize around the dug in teeth, but hopefully the teeth still provide low resistance.