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Supreme Being
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Last Login: 23rd August 2010 20:19
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Bit of a puzzle to me, this one. The XT has been laid up for 3-4 weeks while I got the stuff to rebuild the rear wheel. Sunday I got it all together and had a successful test ride. Monday I set off to work and at the first junction it backfires and dies. I assumed it was running out of fuel, switched to reserve, restarted, and all was well. Work and back, all fine. Tuesday, work and back (25 miles) all OK. This morning, it seemed fine until I switched on the headlight in a bit of drizzle. Within half a mile it had started misfiring, backfiring and losing power big time. I switched my route to side roads away from the traffic and it stalled. It restarted fine, and idled away like nothing was wrong, but when I got going it could barely pull 20 mph in 2nd, with a really bad misfire and a lot of banging from the exhaust. It had no problem idling, but as soon as it was asked to do work it misfired badly. I was about to head for home when I decided to turn off the headlight. Within a few seconds the misfire cleared and it ran like a good'un, and I decided to head for work again. It got me there with no further problem - another 6-7 miles with the headlight off.
My first thought was a blocked jet, but the fact that reducing the electrical load seems to have corrected it makes me think it's electrical. But what? There's plenty of juice in the battery to start it, so it's not a dead battery. But I can't think of any way that turning on the headlight should make this happen. Anyone got an idea?
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2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
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Supreme Being
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Last Login: 16th May 2010 15:09
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| Now, there's unusual. I've known it work the other way: turning the headlight on calmed down a misfire. That was a faulty reg/rec in the early stages of overcharging: the extra load from the lights presumably dropped the voltage to an acceptable level. So it could be the reverse of that: insufficient charging voltage to take on the extra load. I don't think I've ever seen an undercharging reg/rec, guess it must be possible though. Duff coil might cause similar symptoms, if it's at the point where it needs full voltage to drive the step-up: wouldn't have thought there'd be anything further into the HT system than that which would have an effect. Of course, there's always the ECU/CDI, which can also be pretty finicky about input voltage. I can't really think of any other explanation, but it should be easy enough to prove/disprove with a voltage check across the battery.
>> ex silens nox noctis <<
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Supreme Being
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Last Login: 1st October 2010 17:26
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| Any progress on finding the fault BD?
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Supreme Being
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Last Login: 23rd August 2010 20:19
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| Well, I've done a bit of investigation. Battery voltages:
Engine dead, not run for 2 hrs: 12.9v
Engine idling: varies between 13.5v and 14.0v
Engine fast idle: varies between 13.2v and 13.6v
Engine idling, headlight on: around 13.9v steady
Engine revving high, headlight on: varies between 13.2v and 13.5v
Battery is fairly new. The faster it revs, the lower the voltage seen at the battery, roughly speaking. The headlight actually dims as you speed up the engine. I haven't met this before  Also, I had it idling on the drive and watched the headlight. Turning the headlight on, it came on bright and then immediately dimmed slightly. When the engine started misfiring, the light was going off and on in time with the misfire. That tells me that something is loose somewhere - a loose connector on the ignition or in the switch would give exactly those symptoms (I think - I can't remember whether the headlight is meant to come on with the ignition or when the engine is actually running). I wiggled the wiring next to the battery while checking out the main fuse, and the problem went away, at least temporarily, but then when I came to re-start it, it's dead as a doornail, no panel lights, nothing. So all the evidence points to a loose connection. But the variable voltage while the engine is being revved? That's a new one on me. The voltage usually goes up from 12/13-ish to around 14-14.4 and stays there on every other bike/car I have done it on. I've never known the voltage go down when the engine is speeded up. Which says faulty reg/rec to me. Day off tomorrow, so I'll start taking it apart and having a 'proper' look. Cheers all.
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2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
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Supreme Being
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Last Login: 16th May 2010 15:09
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Interesting that the idle voltages aren't way out, but the drop on higher revs is peculiar. Could be the reg/rec, but it might also be worth checking outputs and continuity across the alternator. It may well be that the main problem is still a loose connection, and the voltage fluctuation isn't normally noticable or problematical, but it sounds like there could be something amiss with one of the stator phase windings.
>> ex silens nox noctis <<
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Supreme Being
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Last Login: 23rd August 2010 20:19
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Oo-er. I have spoken to a couple of XT Xperts (cough) and the consensus seems to be a faulty reg/rec - a common fault, it seems. I nearly ordered one today, but by the time I had got the old one off the firm had shut up shop for the weekend, so it will have to be Monday now. If I get some time tomorrow (I am working, chiz chiz) I will do the chacks on the stator. I have the procedure and the specifications in the manual, so it should be straighforward.
Thanks.
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2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
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Supreme Being
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Last Login: 16th May 2010 15:09
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| Chiz? Would that be quoting from the classics - in this particular case "Down With Skool", perchance? That's the first book I shall be buying for my little nephew as soon as he's old enough to read... Off-topic for a brief moment, I've been meaning to ask after Mrs BD - is she fully recovered and fighting fit now?
>> ex silens nox noctis <<
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Supreme Being
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Last Login: 23rd August 2010 20:19
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To take the last question first, sadly, no. She was coming along fine, and then asked why she was coughing up pink stuff, and they found she has a pulmonary embolism on top of everything else. So there's a) a whole new world of treatments to get through, and b) an instruction not to exercise until the blood tests are under control. One step forward, two steps back, at the moment, and she's pretty depressed about it. It looks like our fabled French bike trip this summer is slowly fading into fantasy. However, there is fun to be had giving her the Heperin injections. I pretend to be Eric Bristow, and she tries not to spoil it by laughing. When you are injecting into someone's stomach and she is cackling with laughter, it can get tricky.
As to the 'chiz', why yes, of course, Molesworth 2. My copies of 'How To Be Topp' and 'Down With Skool' were tatty and falling apart, so I bought the complete works in hardback - the two books I had, plus some other stuff I hadn't seen (Wizz for Atomms, I think). Funnily enough, when my eldest daughter was old enough, she started reading them and is now (at 25) a big fan. She still writes 'ect' for 'etc'. She went to a mixed state school, so the humour must be more than just for little boys like me and thee 
As to the bike, I checked the stator resistance, and it was within spec. At least, the spec is between 0.52 and 0.89 ohms, and my meter only reads down to tenths of ohms, so I took a reading of 0.9 as 'near enough'. So I am pretty sure it is the reg/rec and have ordered a new one, plus an extra tenner for next day delivery. Total nearly 70 notes. Ouch.
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2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
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Supreme Being
Group: Forum Members
Last Login: 23rd August 2010 20:19
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Bingo! Fitted a new reg/rec today, and have just done 40 miles with the headlight on, no problems. Charging voltages now normal, i.e. about 13.5v at idle, and going up when you rev the engine, the reverse of what was happening before. Bike now healthy, I hope, and back to commuting duties. Now to sort out the Pan and its little issues.
Thanks to all for the input.
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2003 ST1300 Pan Euro
1995 Yam XT600E
http://goingfastgettingnowhere.blogspot.com/
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Supreme Being
Group: Forum Members
Last Login: 16th May 2010 15:09
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| Sorry to hear about the complications, that's pretty rough luck. Hope for a loooong summer, perhaps, but best wishes for a full and fast recovery anyway. It's good to see that the next generation can still get a quality education and appreciate true literature, though! Funnily enough, I did something similar recently - although it was a paperback edition - spent a mirthfilled couple of evenings re-reading the complete works. Also good to hear it's just (!) the reg/rec - that's plenty enough cost to be going on with. I wonder if it's a common feature of Yamahas that they fail "low"? I've mostly had Honda ones go and they always seem to overcharge - as do the dealers*, especially when you need to replace the boiled and warped battery as well. * Apologies for the pun, I couldn't resist...
>> ex silens nox noctis <<
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