Motorcycle Repair: Honda TL 125, honda tl 125, honda tl125

Question
Hey Bill
I have great interest in old Honda fours especially dirt bikes. I am restoring a 78 TL 125 and are having troubles with spark. As per original diagram conections are good but it appears spark is weak and perhaps erratic. My knowlage of electrical is limited to knowing the conections are all good. Is it a problem with these motors that the cam wore into the head and as a result gave erratic spark as in the early 72/73 CB 125 which I have as well. Perhaps generator or coil is the first to look at

The plug is very carboned when i have run it.How many turns from closed is the usual mixture screw. Normal sparkplug is in.

Cheers Brenden Smith West Australia

Answer
Brenden, I don't have a lot of references to a 1978 TL125. Here are a couple of good websites for references, though.

http://www.kaila.net/tl125/
http://www.users.globalnet.co.uk/~worsfold/TLpage1.htm

If your bike is 1976 or later, it would have the two-piece head, which doesn't have those loose cam issues, unless the cam has been seized for lack of oil.

If the cam is steady in the head bearings, then turn your attention to the points next. The point faces must be clean, shiny and gapped to about .014" and then set to open at the F mark, by moving the points plate around.

Start with the mixture screw about 1 turn out.

Generally, when spark is erratic, either the points are not gapped properly, they are dirty, or more likely the condenser is failing The condenser is mounted atop the ignition coil.

http://www.cmsnl.com/honda-tl125-trials-k2-usa_model747/partslist/F++09.html

The coil should have about 4.5 ohms resistance I think, measured across the two small coil wires.

Bill Silver