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86 xr600 won't rise from dead

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hi crew my names Rhys 21yr old motorcycle courier from Australia. Im hoping someone can pass me a silver bullet for my bike so I don't have to use this lead one on myself...

bike died after a long run of ignition related issues I would've fixed at the time but didn't have the cash. on its final run 2 weeks ago it took 10 mins to start, popped a mono off the curb and reluctantly carried me to my friends house down the rd (backfiring sputtering etc.) next morning I had sort of recovered but the last of the v8s was dead to the world. since then I've been camped out in a shed and have rebuilt the entire bike from bare metal frame. relevant work: replaced stator (which was fried) with a high output electrosport model. replaced plug with a new one. top end rebuild with JE 10.5 1 630cc cleaned head, valves seem fine (I think) lost lower decomp cable so lost the top one too to try and balance things out...

cleaned carbs stock jetting(I know) needle clip #3 fuel screw 2 turns out

all back together and no spark. checked coil @ 7 ohms

replaced coil with a 15 ohm Bosch car coil.. replaced the lead too it was cracked.

also took apart the entire wiring harness and went through it all with a multimeter before reassembly all A1.

cleaned all contacts and connectors.

currently all aux circuits lighting etc are disconnected and the only connection from the stator is the red/black ignition wire.

I still have no spark have tried roll starting putting the plug on my tongue while kicking etc..

have resistance checked the guy down near the clutch (pulse gen?) Checks in spec. I swapped the rectifier/capacitor with a spare all earth connections good everything seems to be good except the bike won't start so I can't work and am rapidly plummeting back to the street.

i've read and searched as much as I can I just have a phone which doesn't want to display the manual I downloaded so if anyone has any suggestions or questions I'd be stoked to hear them.

I'm at my wits end with this and am not keen to fork out $400 and a 2 week wait for a new non refundable CDI unit.

cheers

Edited by sprucegooseduck

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1.) checked coil @ 7 ohms replaced coil with a 15 ohm Bosch car coil.

 

It sounds like you have a multitude of problems, but this is probably the biggest reason you have no spark. The stock coil is a CDI coil for capacitive discharge ignition. At 15Ω, the automotive coil you put on there is an inductive coil and not compatible with CDI ignition.

 

Inductive coils need to charge at 8-12v for a few milliseconds (determined by dwell) on the primary winding before they can deliver full power through the secondary. CDI coils accept a very short, high voltage pulse on the primary that results in an even shorter and far higher voltage discharge on the secondary.

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Young man you've got a bad pick-up coil. I've Had three of these stupid things fail on me on three different XR's I was racing my little brothers '84 250 at a national H&H here in Utah. My Husky 510 was down, waiting for parts. I had to run the race on something because I was in first place standing in my class (4t expert) I had problems with the ignition system before I left the pits on the third loop, but I went out anyway. it would run for a while then die.I'd let it cool down and it would start back up. until it didn't start anymore. DNF!. My bro was pissed cause his bike was only 3 months old. when I found out what was wrong and pulled it out of the right side, under the engine cover the plastic encapsulating the pick-up was melted! looked like a big drip hanging off of the pick-up. Oil in your engine gets HOT! I missed the #1 plate that year by 2 points....DAMMIT!

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damn that's rough mate.. good point though I replaced the ignition coil, lead, cap today with OEM new and still nothing.

the pulse gen pickup checks fine as far as resistance goes... guess it could still be fried?

at this point the only things left to replace are pulse gen, CDI, voltage regulator and the other shindingen CDI looking potted black box that sits behind the headlight...

Edited by sprucegooseduck

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Removed side cover to inspect the pulse gen and it looks fine not melted or anything.

I also found a 20c coin wedged between the coil and a gear which I think may have been a contributing factor. ReBuild engines for speed not on speed kids.

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Removed the coin, checked gap at pulse gen, unit visually fine, measures in resistance spec, wires are in good condition... the bike has never run with the coin in there didn't do any damage must have left it in there when I replaced the clutch

Still no spark.

Has anyone ever heard of CDI failure on old Xrs? I

I don't understand how it could be anything else at this point.. unfortunately the new one won't arrive for 3 weeks so I can't work till then n if the CDI replacement doesn't fix the issue I'm really screwed.

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