Motorcycle Repair: Honda XL100 1973, honda xl100, neibor

Question
Dear Chris,

Im so excited that there are people out there who are willing to volunteer their time to the less knowledgable. Thank you. My neibor has a Honda xl100 1973 road bike. It appears from looking at the speedometer that it is capable of 150+ MPH?
Well shes been using it to run down to get grocieries and since she recieved the bike as a gift a few months ago it has only been capable of 25-30 mph. So I put a better (not new) spark plug into it and I cleaned out the carburetor and I could get the bike to start, but it wouldnt idle. So I pulled out the two screws on the side of the carb and I know that the idle screw is supposed to be pointed but Im not sure if Im even supposed to mess with the other screw. Well the idle screw was almost flat on the end it was really round. So I dremmelled the tip and put it back in and started it up and with a few very minor adjustments to it and the throttle cable and I took off down the road and it almost felt completely fixed! I probably hit 50 or 55 and when I went to turn around it died. I had to keep adjusting the cable and screw to get it to run again and I got it back to her house. Now I screwed the other carb screw all the way in and Ive messed with the idle/throttle for about an hour and I can get it to start, Idle, but when I go to drive it; I have to have the throttle all the way open and just have the bike in first gear just to move at crawling speed!  If you can help, I would be extremely in your debt!

Thanks for your time!

Brandon

Answer
Hi Brandon.
 Sorry, but it sounds like all of your attempts to get this bike to the unrealistic (for that bike) speed of 150 has cocked it up fairly well.  Among the things that sound to be messed up is the mixture, which is critical to every other operation of the fuel and ignition combination as it relates to engine operation.

 You need the repair manual for the bike.  The best speed that you will consistently get out of that bike is going to be about 40 - 50.  That is absolute.  Just because a speedometer says that a bike can do this speed or that, does not mean that it actually can.  Speedos are made to cover an entire range of bikes that require a certain size instrument with a certain size wheel.

 At one point I had a bike that the speedo stopped at 80mph, but I could get it up to 125.  Conversely, a moped has a speedo that goes to 60 or 80, but can't get over 30.

So go out and get the repair manual and start from scratch and retune the bike to what the specs in the manual require.  At that point, the bike will run correctly and be able to get it's maximum speed.

Let me know what happens.
Good luck.
FALCON