Yamaha YB100 problem, please help.

[russeleoin]

Hi All, I am hoping someone can help with some idea's on a problem I am having. My YB100 (6volt) has been running perfectly for a year now. Last week I noticed when I turned the key on, the neutral and oil lights dimmed quite quickly. When the bike was running all appeared well, but I dont ride too far so it was hard to tell. Thinking I had a poor earth, I have cleaned and proved all of them. The battery is now dead( well damned close, 2.4v) it was new 7 months ago and not a cheapie either. I connected my multimeter and see that upon revving the engine the voltage rises with the revs to around 7.5v so I believe the charging circuitry is working. But the problem is getting worse, unless I speed up the idle, it will cut out and upon riding, it is back firing and only appears to be firing on every second stroke. It has no power. I left the battery disconnected and as it should, the charge rose slowly. I think the battery is good, but am running out of things to try. I checked all the wiring now, it is in very good nic, and the few joins in the wires, I have soldered and covered with heatshrink. I am left thinking that it could be the rectifier, resistor or worst case, the alternator. Any ideas would be fantastic as I have run out, but will need to get to work on Monday!
Thanks and regards

Russ
____________________
I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[MaybeGuy]

fuse
____________________
Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[russeleoin]

Hi Matt, nope fuse is still good.
____________________
I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[russeleoin]

No one got any idea's?
____________________
I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[MaybeGuy]

tried charging the battery?
in the haynes manual on the RXS i owned, it said that the battery should be charged off a charger if long journeys arent taken.
mainly because the 6 volt system is a load of shit and cant really cope.
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[ms51ves3]

[stinkwheel]

The battery has absolutely nothing whatsoever to do with the ignition system.

Your battery charging problem and running problems are almost certainly not related unless something has taken out both coils on the stator plate (unlikely it would be running at all if this were the case).

So, charging problem could be the rectifier or could be a loose/damaged wire somewhere (Last time I had a charging fault on a YB it was in the wiring for the headlight, which pinches half the charging coil output when on). Don't panic, it's a single phase, half rectified system so it only has a diode in there to act as a rectifier, they only cost a few quid.

For the running problem. Change the sparkplug, check the points, check the plug cap and HT lead, test the coil. Lastly, replace the condeser. It is very unlikely to be a carburettion problem because it's crankcase induction and the carb is well protected.

To replace the points or condenser you need a rotor puller. The one for a Honda C90 fits perfectly and they only cost a tenner.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[russeleoin]

Hi All. Spent the morning tracing problems and found the rectifier is dead. Would this cause the problems I am having, I can understand the battery is not charging, but when I connected the multimeter, I was connected from battery positive and battery negative and it was more that 6v. Could my auto detect meter be picking up the alternating current? then when I switched off, change to detecting DC? I am hoping to get a rectifier from Yambits, but if any 6v one will do, I will try RS as they are just across the road. I asked on teh Yam owners site if it would be worth converting to 12v. Does anyone have a view on how difficult this would be( lights on the YB are piss poor).

Thanks
Russ
____________________
I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[stinkwheel]

To get 12v out of it you'd almost need to replace half the bike, not really a viable option.

A Honda C50 one will work. You'd need to change the terminals is all. They cost in the region of a fiver.

Yes, the output is AC if the rectifier is dead. If your meter autodetects, this is what will be happening. Measuring D.C. will probably give you a flatline.

It MIGHT have cooked your battery (it's been trying to charge it backwards half the time) although a battery that holds charge isn't strictly necessary on a YB100.

I'll repeat, this does NOT explain why it is running badly, only why the flashers and dash lights aren't working properly.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[russeleoin]

One step at a time. I will do the rectifier and see if the running problem goes away. If not then I shall deal with that. I will however get the pulling tool as I think I will need one when I replace the points! and cant justify paying someone to do that job.

Stink, saw your comment on airtools. Good man, I love mine.

Russ
____________________
I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[russeleoin]

Okay, so I bought a couple of new rectifiers. Stuck one in and started the bike, ha, it started and I thought all was well. Seconds later the farting and spluttering started. Current symptoms are:
1.On kick-start unless the throttle is open wide it will not start but as soon as it does it revs well.
2. If I slowly return the throttle the bike will settle into an even idle for about a minute, then it will splutter and die.
3. The plug is wet and black which indicates a worn engine or ignition problem. I checked the gap it is fine, and the plug is only a few months old so I havent ordered a new one.
4. The points gap is fine, but the points are a bit worn(I have already ordered new ones+condenser+coil)
5. The battery is still dead but after a few minutes riding up and down the driveway it held it's charge better. Now the neutral and oil lights dim after about 30seconds( previously they would come on and dim almost immediately).(New Battery ordered)

Can you think of anything I havent covered. I cant believe it is a worn engine as it was working perfectly one day then stuffing around the next. It still does 55 easily and I can get to 60 on a straight and a fair wind but I dont tend to ride hard as it is really to take me the 8 mile round trip to the station and back. I am not too fat! 82kg and I do look after the bike, it is garaged and cleaned after being in the rain.

I am however getting pissed off as it has been off the road now for nearly a week, and she how must be obeyed niggles about driving me to the station in time for me to get to work!.

Regards
Russ
____________________
I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[stinkwheel]

There is no seperate setting for points gap and ignition timing. Setting the gap ought to put the firing point within the correct "window" of acceptable timing.

If the points are badly worn, setting the gap correctly will lead to retarded ignition timing. A black sooty plug with a loss of power are a symptom of retarded ignition timing among other things.

Could also be the condenser, a dead condenser can cause scorching of the points and a weak spark.

Maybe worth checking the air filter is clean and the exhaust baffle isn't too coked up at the same time.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[russeleoin]

Thanks Stink, will check on the airfilter this evening. I bought a new pipe for the MOT in Jan so it should not be clogged, ut will check that too. My bits should arrive tomorrow, so I will fit them in the evening.

I have just removed the rotor, managed to get my small bearing puller to do the job. The points are definitly worn, it will be good to get them replaced. I hope my strobe works on this so I can set the timing.
____________________
I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[bikedemon99]

The manual should give you advice with metering the output and circuit testing, personally I think it will be the rectifier but you really will have to start checking everything and even for broken wires and I take it youve set the gap, good luck with it
____________________
Ride safe

[stinkwheel]

[russeleoin]

The end of the saga. Well, all my bits arrived, battery, coil, points and condenser. All of which were replaced and guess what, the problem remained!. I couldnt believe it, I nearly cried. I measured circuts and all sorts and still had a problem. The bike would start but would not run smoothly unless it was revving high. I checked everything I could, and the by accident, I pushed on the key while adjusting the idling and the bike cut out. A bit more fiddling the problem was proved, the key switch is faulty, it seems to be arching across to earth. The reason it happens at idle is, that is when there is a bit more vibration, if I held the key still it ran fine. Anyway, I needed the bike for work so rather than replace the switch as I would have had to wait for it to be delivered, I have wired in a small kill switch. So now I use the key switch for lights and the kill switch for engine!. Still I am happy as I was able to ride this morning problem free.

Thanks for all the suggestions.
Regards
____________________
I love classic merc's but bikes take up less space.
Current ride is a Yamaha YB 100 and I love it! Oooow and now a running GPZ400R!
Next stop, Direct Access hopefully by the end of summer.

[stinkwheel]

Ah well, no harm done. You know the points and condenser are good for a lot of miles now if nothing else.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.