hi
is the xxt 550 the same as an early xt 600 one if so has anybody got one as i really deperate
cheers
Dave

Ummmm - what piece exactly, Dave?

Still having electrical problems, I guess?

hi,
yes i am,i guess i should have given more details. i believe the cdi unit is playing up as sometimes the bike starts and when it is it runs it runs pretty well. then it wont start at all,although i have a spark and petrol?
Dave

Intermittent issues are more likely to be a bad connection than the CDI playing up. CDIs and the like generally either don't work at all (due to burned out diodes or blown caps) or will work and then cut out after a while due to overheating.

If you're getting a spark but the bike won't start, I would strongly suspect a bad connection at the coil, probably on the HT lead or plug cap. how are you testing the spark? "plug out and held against the casing", or "cap off and spark from the HT lead itself"?

I'd check *all* connections from the coil, especially the earth connection and HT lead, a good idea would be to pull the cap from the plug and test connectivity / resistance between the plug terminal and earth whilst jiggling the lead about.

Another possible issue would be a weak spark, there's a few things that could cause this.

First off, are the ignitor coil resistances (as measured between the red and brown wires from the alternator) in spec? If this is low, you have a stator rewind in your future (probably a short in one of the coils, and your spark won't be as "hot" as it should be). Coil resistance should be of the order of 150-250 ohms or so (although your manual should have the exact figures)
While you're there, make sure there's no connectivity between either of these connections and earth, even when jiggling the wires.

Next up, are you getting a good connection from igniter coils to CDI? This one is kinda hard to test, as the wires are sealed at the CDI end and there's only one pair of connectors for the ignitor coil feed. Basically, if the wires to the CDI are fecked, you might only be getting an intermittent spark, or if the connectors are corroded to buggery you might not be getting the current you want (although the voltages might look fine). Like I said, it's a bitch to test. Check the CDI wires for obvious breaks, clean those terminals (red and brown again) as well as you can, plug and unplug a few times to get a decent connection. Do the same to all the other connections from alternator to CDI at the same time (the 3 pin plug with white-red/green/white-green), you *know* you want to.

You can test the output of the igniter coils with a multimeter set to AC volts, 2000V range or so IIRC by connecting your multimeter to the brown and red terminals *without disconnecting them* while the motor is running. Easiest way to do this is to make a pair of pigtails with "plugs", connect them to a "domino" terminal block and then gently fit the existing "plug" connections into the domino, that way you can take readings from the screws in the terminal block... If the manual gives amps rather than volts, you can connect a meter inline to see what the output is.

Resistance of the brown-red connection on the CDI should be roughly the same as that of the igniter coils. If that is out of spec per the manual, your igniter is definitely dead.

While we're on this side of the CDI, might as well check the pulser coils, generally you have 100-150 ohms or so between the center tap and each leg (so, green to white-green and green to white-red)

That's about all you can do this side easily and without an identical, known good, igniter and alternator.

Now off to the "hot" side.

There's bugger all you can do to static test the hot side of the CDI, so check the orange, black and black-white connections are good, then it's off to the coil.

Coil primary resistance (orange to black) should be under an ohm, probably 0.5 ohms or so. check your manual for the exact figure

Coil secondary resistance (HT lead connection to black) should be in the 5000-10000 ohm range. again, use your manual.

Testing the coil output is potentially lethal, I'd avoid it if possible. You're dealing with tens of kilovolts when the motor is running (usually between 10 and 30Kv or so, depending on motor regime)

Other stuff to check is all the gubbins that hangs off the black-white lead from the CDI. Kill switch, main switch, etc. With everything turned to "run" check continuity from earth to where the CDI plugs into the loom. The kill switches and the like all work by *earthing*, so there should be zero continuity here with everything set to run. Also check the black/white lead of the CDI for continuity to earth.

If you're seeing continuity in the loom, there's a short somewhere. Isolate by slowly unplugging switchgear and testing (kill switches are notorious for dying), if you have the kill and ignition switches disconnected and you still have continuity, you have a short in the loom itself (and good luck with that)

Simon

Oh, and in reply to the original question...

XT400/550 CDI is Nippon Denso 5Y3-85540-50
XT600 34L CDI is Nippon Denso 07000-1080

XT400/550 coil is Nippon Denso 5Y1-82310-50
XT600 34L coil is Nippon Denso 129700-089

It's highly probable that the 34L CDI and coil will work more or less fine with the 550, although the advance curves are different and you may have problems at higher regimes (the 34L advances to 36° at 4500RPM, 550 to 35° at 6500 RPM), but I'd check out all the connections before considering transplanting CDIs from anything other than a 400 or 550.

And a new plug probably wouldn't hurt if you haven't already.

i will second tuftys last bit of advice..

try a NEW PLUG... but DO IT FIRST, you would be amazed at how many times the plug has been the problem on bikes i have worked on, also a worn plug takes a much higher voltage to produce a nice fat spark than a new one.

may i wish you a fast fault find as electrical problems are the worst type of problems, or at least they seem to bring out the worst in us, in terms of frustration, tears and banging head against shed wall!

Any joy, Dave?

hi Simon,
no not as yet,just not had the time which is bloody getting on my nerves.
waiting on a cdi .will keep you posted
cheers
Dave

Simon,
i have checked the wires from the alternator and all appear to be within the tolerances that they should be. the old one had lots of dodgey wires the other one that i replaced it with did need some new connections etc,so i am fairly confident that my cdi is playing silly buggars.
i have just got to try and find one as i missed out on the one that i was after!
Dave