Motorcycle Repair: Honda xl100 1973, honda xl100, bike expert

Question
Dear Mr. Hendrix,

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
Brandon
Let's get a couple of things out of the way first. I am a BRITISH bike expert, not a Japanese bike expert. Honda is Japanese built. I can't be of much help.

The only X1100 Honda I know of from that year is the CBX six cylinder. This was a frighteningly fast machine, but was also a little bit tempermental. Lots of opportunities for things to go wrong with a machine that complex. Now you are dealing with a bike that is over 30 years old.

Tuning and maintenance of this piece of sophisticated wizardry should only be handled only by a trained Honda mechanic.

I'm confused, though. There ought to be a whole bunch of spark plugs and carburators to deal with. You make it sound like there is just one. Are we thinking about the same bike?

Better spark plug? How do you define better? If it wasn't new, it can't possibly be better. Where did it come from. Was there only one? There is too much risk in that one. I have had plugs that looked beautiful, but were dead as doornails. Don't ask me why. It's just one of those things that happens.

The unfortunate part of this is that you started messing with the carb(s) without the thorough knowlege necessary. The problem may be something as simple as a clogged fuel line. On Most of the bikes I have dealt with, the idle screw was usually flat on the end. The air mixture screw is usually the pointed one. I hope you haven't done too much damage at this point.

My advice to you is to find the proper manual for the thing. Find the proper tools. Then, examine and repair all tune-up items one at a time.

Don't try to go cheap with this, you will only fail. If it needs new plugs, buy new plugs. If it needs new carb gaskets, replace them. Same with points.

Good luck. Take your time and take care.

John