Author Topic: Xbr500 wiring  (Read 2263 times)

Propellor

  • Posts: 1187
Xbr500 wiring
« on: July 28, 2013, 05:20:03 PM »
Hi

My bro is restoring/customising a 1988 model xbr500 and we are on with fully re wiring the bike. It no longer has the electric starter motor or the standard clocks. He wants to eliminate as much of the std loom as possible.

We have a problem that we can't get a spark at the spark plug and wonder if we've eliminated something in the circuit associated with the electric start safety features, which is now preventing a spark?

Not much to go on, but any tips anyone?

Thanks.
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Smithy

  • Posts: 827
Re: Xbr500 wiring
« Reply #1 on: July 28, 2013, 07:51:50 PM »
Probably not going to be much help but I will have a try. I used to have an XBR and can't remember if it was too old to have a clutch switch. This is usually a small micro switch operated by the clutch lever that prevents the bike being started in gear unless the clutch lever is pulled in. Also check the kill switch, some work by connecting the wires others by earthing them so check your switch is allowing the engine electrics to operate.

Failing that ask the elctrickery pushing pixies to push harder.

guest1670

  • Guest
Re: Xbr500 wiring
« Reply #2 on: July 28, 2013, 08:17:27 PM »
If I were you I would rule out a faulty coil first. If my very basic knowledge of electrickery serves me correctly, you should have roughly the same volts at the coil as you have across the battery. This is how I would check it. Disconnect the two wires at the back of the coil, turn on the ignition and use a multimeter to check for voltage. Red lead to wire, black to a frame earth. One of these disconnected wires should show voltage, which proves you are getting power to the coil. Plug this wire back on, and check across that terminal to the other, unwired terminal. You should have voltage here too, which proves you have power through the coil. No power=bad coil.

If this checks out, the lead, cap or plug could all be at fault. To check for spark, lay the plug somewhere on the head - it has to be physically in contact with something, not just hanging there.

If you found no voltage at the coil you can systematically follow the wiring back to find the fault (I think!).

As I say, I'm no expert but this is how I would do it. If there is an electricity guru out there who can suggest a better way, I won't be offended to be corrected!

Propellor

  • Posts: 1187
Re: Xbr500 wiring
« Reply #3 on: July 29, 2013, 06:10:18 AM »
Thanks guys. We're going to check how the kill switch is wired. On my old Beemer it was simply a break in continuity, so easy to fathom. The x beast r may be different.

The info on coil checking is appreciated. We'll get right onto it!

I wondered if, by removing a lot of the circuit associated with the starter motor, we'd inadvertently left something to do with the safety gadgets permanently earthing out the ignition. There are wires going into the cdi unit to do with this and we're not sure if we need to connect them up?

Also, anyone know what the little black object in the neutral light circuit is? The wiring diagram shows it as a diode or transistor I think?

Thanks again.
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Propellor

  • Posts: 1187
Re: Xbr500 wiring
« Reply #4 on: July 30, 2013, 05:52:02 AM »
What is the recommended method of checking the ignition pulse unit? The pulse unit is only a positional device? So we should get a spark, even if it is mis timed. How about checking the cdi?

Cheers
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Propellor

  • Posts: 1187
Re: Xbr500 wiring
« Reply #5 on: August 02, 2013, 07:17:36 AM »
We now have a spark. Albeit a weakish looking one. We only have a kick start on this bike, but the battery is fully charged and checks out ok on the optimate. We have a second xbr in the garage which we know runs fine and that too has a fairly feeble looking spark.

What is confusing is that, although we have a spark, we aren't showing hardly any voltage at the connector which goes onto the coil (not the earth side). We checked the other bike and the same applies to that. This is slightly mystifying.

When I worked on rewiring my old Beemer, that showed 12 volts at the coil. But then it doesn't have cdi ignition.

Any ideas?

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SteveC#222

  • Posts: 1900
Re: Xbr500 wiring
« Reply #6 on: August 02, 2013, 07:33:05 AM »
What did you do to get the spark back?  I have pretty much the same problem with my XBR which has stood for 18 months and I'm struggling. The resistance readings I'm getting are different to the manual ( may be my multimeter) and I don't seem to have any voltage going into the HT coil.  I'm slowly working my way through so any hints would be much appreciated!!
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guest295

  • Guest
Re: Xbr500 wiring
« Reply #7 on: August 02, 2013, 08:28:03 AM »
The BMW has battery ignition; the XBR should get its spark entirely from a coil in the alternator. If it runs at all, it should run without the battery. The spark is a bit weak when you kick it over because, of course, the voltage is just barely enough to make a spark. Once it fies, it should get more volts.

Propellor

  • Posts: 1187
Re: Xbr500 wiring
« Reply #8 on: August 02, 2013, 11:56:41 AM »
The BMW has battery ignition; the XBR should get its spark entirely from a coil in the alternator. If it runs at all, it should run without the battery. The spark is a bit weak when you kick it over because, of course, the voltage is just barely enough to make a spark. Once it fies, it should get more volts.

Ah, that makes sense then. Thank you very much for reply. It is helpful and appreciated.

Since the bike is kick start only and has a high compression piston in there, is there any electrical mod which can be made to make it a better starter? Like a switch to switch over from a battery fed coil to the standard supply once the engine is running?
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Propellor

  • Posts: 1187
Re: Xbr500 wiring
« Reply #9 on: August 02, 2013, 12:17:02 PM »
What did you do to get the spark back?  I have pretty much the same problem with my XBR which has stood for 18 months and I'm struggling. The resistance readings I'm getting are different to the manual ( may be my multimeter) and I don't seem to have any voltage going into the HT coil.  I'm slowly working my way through so any hints would be much appreciated!!

The answer is simple. We think we always had one! We just weren't kicking hard enough! Plus the spark is "thin" so not easy to see, especially against the aluminium head and the fact that each kick moves the bike a lot.

Basically we started undoing every bit of sheathing on the original loom and started to build our own very much simplified loom. When we got enough wires in place to theoretically provide an ignition switch, fuses and an ignition circuit we tried for a spark. Because we thought we weren't getting one we tested for voltage at the coil and found virtually nothing so assumed that by leaving out all the circuit for the starter motor and all the various "safety" devices, that we'd inadvertently shorted the coil or something.

My bro has another xbr in standard ish trim, with a starter motor, so we tested that for a spark using the starter motor. We got a spark albeit a slightly "thin" looking one. We then tried the kick start and at first the spark seemed to have gone AWOL. But as we'd had a spark by the starter motor only minutes earlier we looked more closely. And realised there was a weakish looking one after all.

We then disconnected all the connectors associated with the bits we don't want on his (my bro's) cafe racer bike to prove that the ignition will still operate. It did. So we realised that all along we'd probably just not been looking hard enough. At this stage the lack of "static" voltage at the coil was still a mystery.

We took our home brewed, half finished loom off the project bike and transferred the loom from the standard bike. We soon were able to produce a spark.

We then tried to actually start the project bike, but to no avail. We gave up after an hour or so of trying, both kicking and bumping. The best we got got was a couple of backfires in the exhaust.

Now that I have a bit more info on how the spark is produced, we can explore further. The carb is a new mikuni slide jobbie so I need to check that is set up right. Then we'll have to check the timing as the engine was sent to a professional builder, who specialises in motocross. We need to satisfy ourselves that the timing is ok and not somehow completely out of sync. We have a spark, but we don't know if it is produced at the right time!

If we can provide anymore info Steve, just ask and I'll try my best! Likewise if you have a eureka moment, please let us know!

Best of luck.
« Last Edit: August 02, 2013, 12:20:59 PM by Propellor »
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guest1670

  • Guest
Re: Xbr500 wiring
« Reply #10 on: August 02, 2013, 12:43:34 PM »
I was obviously way off!!

Although in my defence my '87 Srx is the newest bike I've ever had! Don't get these new-fangled CDI thingies on 50 year old Brit twins!

Please keep us updated - I'm learning something here!

Martin

Propellor

  • Posts: 1187
Re: Xbr500 wiring
« Reply #11 on: August 02, 2013, 01:13:39 PM »
I was obviously way off!!

Although in my defence my '87 Srx is the newest bike I've ever had! Don't get these new-fangled CDI thingies on 50 year old Brit twins!

Please keep us updated - I'm learning something here!

Martin

Hee Hee. If I'd a quid for every time I'd said that.....

No worries. I appreciate the input anyway. The fact that you're thinking is good. It beats watching soaps any day.

Cheers.
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guest564

  • Guest
Re: Xbr500 wiring
« Reply #12 on: August 02, 2013, 08:09:44 PM »
My 1985 had a 'boost' switch connected to the starter button, if yours has that then it might be worth wiring that up to give a little extra when starting. I did experiment with this on my racer but the coil saturates at something like 2000RPM so it wasn't any good for a racing bump start.

Propellor

  • Posts: 1187
Re: Xbr500 wiring
« Reply #13 on: August 03, 2013, 08:59:55 AM »
My 1985 had a 'boost' switch connected to the starter button, if yours has that then it might be worth wiring that up to give a little extra when starting. I did experiment with this on my racer but the coil saturates at something like 2000RPM so it wasn't any good for a racing bump start.

Thanks for that info. Looking at the spec of your bike you are SERIOUS about your xbr's!

When you say booster "switch" I assume you mean some device which is switched in automatically and not manually? And that once we've determined that it is on our machine, we arrange to switch it in and out manually as needed?

Next (and predictable) question. Where will it be? What are we looking for? What is the symbol for it?

We tried bump starting the bike several times, with a bit of a gradient to help. We had the engine pumping several times but still no go! This is what makes me thin there is something perhaps more fundamentally amiss. Like the timing for example. We have two of everything; coil, cdi, rectifier etc and one set was known to work fine, so that helps.

I don't suppose it is possible to have the pulse generator 360 degrees out because we have a four stroke and I assume every other pulse is "wasted"? Then again you wouldn't want to employ the wasted spark principle surely, as this would halve the response time for the capacitor? Have I got that right?
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Propellor

  • Posts: 1187
Re: Xbr500 wiring
« Reply #14 on: August 03, 2013, 09:01:40 AM »
My 1985 had a 'boost' switch connected to the starter button, if yours has that then it might be worth wiring that up to give a little extra when starting. I did experiment with this on my racer but the coil saturates at something like 2000RPM so it wasn't any good for a racing bump start.

Thanks for that info. Looking at the spec of your bike you are SERIOUS about your xbr's!

When you say booster "switch" I assume you mean some device which is switched in automatically and not manually? And that once we've determined that it is on our machine, we arrange to switch it in and out manually as needed?

Next (and predictable) question. Where will it be? What are we looking for? What is the symbol for it?

We tried bump starting the bike several times, with a bit of a gradient to help. We had the engine pumping several times but still no go! This is what makes me think there is something perhaps more fundamentally amiss. Like the timing for example. We have two of everything; coil, cdi, rectifier etc and one set was known to work fine, so that helps.

I don't suppose it is possible to have the pulse generator 360 degrees out because we have a four stroke and I assume every other pulse is "wasted"? Then again you wouldn't want to employ the wasted spark principle surely, as this would halve the response time for the capacitor? Have I got that right?
BEIGE is all the rage