Install a 16 Tooth Front Sprocket

[bmw633]

Without a tachometer, how does one know whether the engine is redlining at WOT. This bike is for my 130 pound daughter to learn to ride. I am also considering a 16 tooth front sprocket to keep the revs down. I just tore down the engine to the cylinder because of low compression, the bike topped out at 50 mph. This is an E-Bay engine I got from Pin Worms (sp.) Motorcycle recycling. They would not even give me a partial credit because it was past 30 days since I got it. It took the shop a couple of weeks to swap motors, then the weather prevented a trip for another couple of weeks. It ran ok for about 50-75 miles, then it started losing power. By the time we got it to the shop it took another week or two for them to find out what was wrong with it. 110 psi compression.

I copied the shop manual and went to work tearing the motor down. I am taking the parts to a machine shop so they can hone/overbore the cylinder walls and new rings, and possibly an overize piston. I noticed while removing the carburetor the black plastic top had a loose screw, which caused the top to wiggle around. Could that be the cause of low power? I am also taking the head and camshaft for a valve job and to check for wear.