Fun times indeed Butch & so are these...just different.
Woke up early and started thinking while drinking (coffee) I'd looked up some information regarding the relative weight of the industrial clone engines (160 cc) & the motorcycle clone variety (CG 125) I used published shipping weights and deducted a few pounds to come up with a rough estimate of dry weight. I'll put in a disclaimer at this point. I'm a fan of both types in varying displacement sizes. Both build out & perform really well. I've used the industrial in multiple go-cart builds back in the day but never on a bike 'cause of a bad Shoulder (rotor cuff) today I don't own a pull start engine...not even a lawn mower, but only because of the shoulder.
Here's what I came up with CG 125 cc, speed & wet clutch, kick start...55 lbs. dry weight. Add 20 lbs for electric start & battery (lead)....75 lbs. total weight.
GX/GC 160, pull start only 25 lbs., Bully clutch 5 lbs., electric start & lead battery 20 lbs. Total weight 50 lbs.
I can't see that the weights of either base engine, 30 lbs. for the industrial clone with Bully clutch or 55 lbs for the CG motorcycle clone with kick start is a problem on a decent frame. The GC with electric is almost the same as the base CG weight so no problem there either. Of course a well designed & installed motor mount is essential to distribute the increased weight & engine torque or even the best of frames could be damaged.
When all is said and done rider weight is just as much of a problem as added weight anywhere in the build. The rules of physics still apply. Big guys put a lot of strain on a bicycle frame motorized or not & this weight needs to be plugged into the equation as well as any additional accessorized weight load.
Un sprung weight factors in pound for pound as more of a problem than sprung weight as well. A good front suspension helps protect the frame as well as the rider. Larger & softer tires help as well. I have a bike that rolls on 24" x 3" tires front and rear, no suspension front or rear that rides like a dream cushioned only by the over sized tires.
A lot of stress is also delivered to the rear triangle on board track builds as a result of our using (yes I'm also guilty) the rear seat stays for primary support of the back side of the boardie racing saddle. I love the look & I've not yet cracked a stay, but I've broken a couple of brackets over the years and confess to almost going down as a result. I was lucky. My brackets have been radically beefed up, but I now wonder what's become the weak link at this point. Now, on frames with a traditional seat tubes, I always utilize what has historically worked best on bicycles. Tube in tube, even on board trackers. I feel it lessens the damaging loads on the frame more than increased engine weight.
In the same vein: use the pedals to support at least a portion of your weight, especially if your a big guy. That's one of the most important reasons bicycles have pedals. Yes you can power & start some of the motors with them & set the coaster brake as well, but keeping some of your body weight on the pedals lessens the shock delivered to not only your spine but also to the bikes frame and components. The strongest area of a good bike frame is the bottom bracket. Directing a good portion of your weight to the bottom bracket lessens the shock to more vulnerable areas of the frame. If you put all weight on the saddle & hit a bump your weight is multiplied by the momentum created and sent directly to the frame. Your legs bearing weight act as springs and rebound control when riding on rough roads. I realize that some are not physically able to bear much weight on the legs. For these a well sprung saddle attached to the seat tube will modify and direct the forces down the tube to the strongest point of the frame, again the bottom bracket. Not as effective as using the legs but better than directing the force to the rear stays.
Thinkin' & drinking...not always very helpful, but I try.
Rick C.
