hello forum , 2stroker here iv'e been a motorized bike hobbies't for over 10 years now and iv'e had 4 friction drive bike and 3 chain driven HT kits, i have here some very useful tips for making your engine and parts last the longest, if you follow these tips correctly your engine and parts should last 3 years or more with little to no problems.
1# "always keep your chain and clutch well lubricated"!, iv'e seen many people completely forget to grease the chain or the clutch bearings, doing so can ruin and break the chain as it jumps off your sprocket and your clutch cable can snap on you. i recommend high temperature bearing grease for both the chain and clutch. plus its waterproof
2# "keep those bolts tight", always make sure your engine mounts have locktite on them, locktite is a medium to high strength Chemical Compound made with Acrylic Ester that basically locks the bolts in place and engine vibration wont affect it, use this on every bolt as you can. i recommend using medium strength locktite.
3# "keep your bike out of the rain", you may think your bikes all waterproof but water can still ruin your motor, if water were to get on the magneto it can make it rust and even cause the wires to rot, if your bike must sit outside cover it with a tarp or even a plastic grocery bag (make sure its cooled down though!).
4# "clean your carb" cleaning a carburetor may very well be the most important of all these tips, if your engine seems to have lost its power it may have a dirty carburetor, you can buy carb cleaner at any dollar store.
5# "go at a reasonable speed", ok so your asking what does this have to do with making your engine last longer, well in a short answer, going slower reduces the stress and heat buildup on your engine, many of us like to go wide open on our throttles, but doing so can cause a massive engine seize or even melt parts of the engine, so if you must keep up with traffic, try to vary your throttle speed and give your engine 15 minute breaks if you plan on riding longer than 1-2 hours at a time.
Hope these tips helped most of you