2wheel newbie

The Yamaha dealership wants $105 bucks for a new voltage regulator. 10 minutes ago, I jumped the power supply (brown wire, changes to black at the connector) of the exciter directly to the battery + terminal, no change in voltage at the battery. I tried jumping the ground wire to the battry -, but the bike just cranked, wouldn't fire. I threw it on the charger and just now tried jumping the ground and power wires to the battery, but it still wouldn't fire up. I think the battery is fried, it maybe a 'cycle battery, but it's not a deep cycle battery. So far the owner has spent $450 for the bike itself and $285 in parts/labor for $735 total. Now the Yamaha dealership wants $105 bucks for a new voltage regulator, plus what ever a new battery costs, should I tell him to sell the bike as it is now and buy a better one? He's used to a lighter, dual purpose bike.

Now that I got the bike running, I gave back the keys, and now it stalls out while the owner is riding, both at idle and when he's accelerating. The voltage is 12.5 to 11.9 volts and it stays at that range no matter what RPMs the engine is at. When it was idling, I saw the RPMS slowly drop untill it died.I've checked the rectifier (diodes were good), the stator and the field exiter with my ohmmeter (both within the specs the Haynes manual said). The only thing I didn't check is the Voltage regulator (manual didn't give any specs). I'm really sure it's bad,and will be replacing it, but I'd like to know if the stalling is a symptom of a bad charging system, and would a bad voltage regulator lead to a dead TCI module?

Never mind, I got it running by sanding off a rather thick layer of build up that looked like metal (but was actually soot) from the spark plug electrodes and hooking it up to my car battery charger and using the 260 amp Start Boost setting. Setting the mix screws to 4 1/2 turns after it had warmed up had it running perfectly. Now I just need to put in a new voltage regulator for the charging system to work.

My neighbor recently bought a 1981 xs400SH, it was running when he bought it. One morning it wouldn't start, so he asked me for help, I'm a car mechanic. I've never worked on a motorbike before, but on a 30year old carb'ed Yamaha, how hard could it be? I grabbed my battery jump pack and got it started. He took it for a quick spin up and doun the street, he came back pushing it and when it went over the curb, gasoline poured out the air filter boxes. I grabbed a drain pan and drainded the tank, I told him that the carb floats were probably stuck wide open. I told him I could easily fix that. I took the carbs off the bike, took them inside, to work on, removed the float bowls, the floats and the float needles. Both needles had rips in the rubber tips. I stoped by the library for a book on Yamaha XS bikes to supplement the Haynes manual that came with the bike, and went to the bike shop for new needdles and seats ($90 ). I put them in, adjusted the float level to 32mm like the books said, put it back to gether with new gaskets. Before I put the carb back I fliped the rubber boot/carb holder thingies so that the vacuum ports pointed up (previous owner replaced them w/o gaskets when he replaced the carb with another one). I reconnected everything, set the fuel tap to PRI, pulled out the choke all the way, started it up. Then it stalled when I put it in 1st choke position and gave it even a little bit of throttle. Wouldn't fire at all with the choke all the way in I went back to the bike shop for advice, they looked at the carbs and tolled me the anti-tampering plugs on the pilot screws were gone and the screws were all the way in. He backed them out 1 1/2 turns. I looked online and MikesXS(dot)net says: "Suggested setting position of the normally hidden mixture screw is 2 1/2 to 3 turns out from bottom." I tried starting the bike at 1 1/2 turn from bottom, 2 turns, and 2 1/2. Would not start at any those I tried. My neighbor had the original carb with the anti-tamper plug still in place, I used a drill and tap to remove them, and the right carb had the needle at 4 1/2 turns. I could'nt find out the left side, the drill went in too far, toutched the needle and turned it all the way in. I swapped the screws with the ones from the old carbs (after soaking them in cleaner over night) and turned them out 4 1/2. Still wouldn't fire. When ever I pull the plugs out, they are damp, but not soaked. I pulled the spark plugs out and held them against the cylinder head. I didn't see a spark jump the gap. After reading the wiring diagram and testing every componant, I replaced the TCI box with a used one ($50), now I get spark, but it seems weak, both coils read 3 ohms on the primary, but I'm not sure how to measure the secondary. Do I remove the plug wire, leave it on but unscrew the spark plug cap, or measure it with everything on? I've also done a valve adjustment, oil change (crankcase was full of gas), put in a new used starter solenoid, new fuses, charged the battery several times with my car batt charger, and gapped the spark plugs to .6mm to help the spark jump the gap. I need advice, I'm about to pick this thing up and throw it in the dumpster.