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Ignition system bad - CR500 85'

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#1
I'm new here and I have just one question so far.

I bought my 1985 CR500 w/o spark. And it still doens't have any spark.

I will go through what I've done step by step

- The ignition system came to me complete, but not working
The previous owner gave me a brand new honda original ignition coil to try to get the bike working so I put it in
Still no spark. Since then I have bench checked the unit and it is indeed good. I have also tried to switch to the old ignition coil (it tested find too, but still no spark)

So I checked the resistance ratings on the stator and pulse generator. They were both fine so I took took a peek at the stator, rotor, and pulse gen to determine their physical condition.
It all looked fine except on of the mounting tabs on the aluminum backplate for the pulse generator had broken off. It had been fixed by a the previous owner with some JB weld, put it didn't stick.

So it seemed like a good idea to me at the time to glue the mounting tab back on the aluminum backplate with JB weld to see if
that was the problem. I don't think it was because I got things lined up pretty damn well, put it was still a no go.

I looked in my CLYMER's manual under the ignition system and it did not have any specifications to check the condition of the rotor or the CDI.

Since the previous owner mentioned the CDI I checked e-bay for a good used unit. I found one and installed it on the bike temporarily. It didn't work, and my old CDI looked a little better, so I just stuck my old CDI unit back on (to check one thing at a time).

So I bought a new used aluminum backplate, stator, and rotor (sometimes called a flywheel). They all looked to be in good condition so I tested the resistence for the pulse gen and stator on this set and it was good. I installed it and crossed my fingers. But it was still a no go. I tried to take off the kill switch too, but still no spark, I have since then tested the kill switch and found it to be good. I tried to use the CDI I bought off EH-BAY with this setup, still nothing.

I have checked the dark green ground wire that makes contact to the frame behind the ignition coil, the only ground wire in the whole setup, and have found it to be good. I have also checked that this wire has continuity all the way to the engine, it does.

Any hints/suggestions?

One thing worth mentioning is that during the test process the rotor has been about 1mm off the shaft. This is because I don't have an impact wrench right now, and It is a pain to pull the rotor if I need to if its really tight on the shaft. Could this be the source of the problem?

The whole engine and frame was painted pretty sloppily, and they even sprayed right over the rotor assembly. could there be a ground there that got messed up or something? I'm really at my wits ends with this thing.

to update you
The woodruff key is good
There is continuity between the coil ground and the motors metal surface
The kill switch is fine :( :(
 
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#2
Oh and the reason this is posted here is because its completely baffiling to everyone else! I've tried talking to many mechs, and posting every which way on the internet, and nothing :yikes:
So maybe some of you advanced technical guys can help?
 

marcusgunby

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#3
With a problem like this the easiest answer is to get a working bike of similar age and swap parts to and from to find the culprit, without doing this your really chasing your tail, have spare parts like you already have is good but you havnt proven either is good, eg at work we have many brand new parts faulty, so you replace a faulty part with a new faulty one and spend 2 days looking for a reason why it doesnt work.Seen this about 10 times in 10 years-its always the hardest thing to work out.A donor machine really is the way to prove it.
 
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#4
Where do you think I can pick up a donor for an 1985 CR500? Just wondering if you have any ideas, cuz I sure can't find anything. Luckily there was a complete ignition revamp in 85 from 84, and then again from 85-86. Anybody know if I can swap for a 250 or 125? I _might_ have better luck that route.
 
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#5
I just can't let this one go
Someone must know something I don't
And I'm damn sure not taking the thing to a shop, cost an arm and a leg
Puh-leeaase with sugar on top?
 
- a d v e r t i s e m e n t -

marcusgunby

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#6
ive heard you can use the parts from a 250 to remove the rev limiter on a 500 but i have no experience of this mod.
 
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#8
Whereabouts are you located, I have the 85 CR5, Once I get her the engine together mabye you can drive over here and we can swap some parts to see whats wrong with yours...
And if you do fix it, let me know what it is, just in case I run into the same thing.
Keep us updated.
 
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#10
This might seem stupid.. But have you checked the cap there goes on the sparkplug? It could have bad/no connection to the ignition lead or it could be corroded inside.. Just checking!! you probably already checked it!

Jacob
 
- a d v e r t i s e m e n t -

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#11
hook the bike up to a siliscope and turn the bike over and see if it picks up any spark on the screen. i had a spark problem before and the spark was so week that i couldnt see it on the plug but the siliscope had picked up a little power. but the ignition did work. also coils will test out as having risistance even though its bad. so maby you need a new coil but that was just my problem with my bike that was a 84 kdx200.
 

marcusgunby

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#12
resistances of coils when off load dont tell you much-they can read ok but not pass any current.
 
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#14
newbikekiller said:
I just can't let this one go
Someone must know something I don't
And I'm damn sure not taking the thing to a shop, cost an arm and a leg
Puh-leeaase with sugar on top?
charlierday :yikes: i got asimaler prob 1985 cr250r no spark ive yet totest parts like more info so i dont make simmaler mistakes im open 4 sugestion may need to buy parts from u i acualy held my new plug kick it slitly felt somthing after about the 20th
 
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#15
dont they update these files

charlierday said:
charlierday :yikes: i got asimaler prob 1985 cr250r no spark ive yet totest parts like more info so i dont make simmaler mistakes im open 4 sugestion may need to buy parts from u i acualy held my new plug kick it slitly felt somthing after about the 20th
 
- a d v e r t i s e m e n t -