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Discussion Starter #1
i have a friends vt500c 1985 shadow that was running great and when he had a passenger he completely lost spark to the rear cylinder almost instantaneously. I have ohm'd out and switched the coils, and those checked out fine, and the tachometer still works which leads me to believe that the CDI box is still good. the bike still runs, but only on one cylinder with low power, but will still go to red line with some coaxing.

I then further tested the pulse generators and one of them is putting out roughly 400 ohms and the other one nothing, I have not pulled all the wires to see if there is a broken one somewhere (I hope this is the cause) but I can't find a replacement anywhere, ebay, local scrapyards or online.

I would like to also find out if there are any locations where there are connectors which are likely to fail. i have not yet opened up the case to visually inspect it yet but i'm almost certain this is the cause.

does anyone here have a parts bike that still has the pulse generator assembly? also, are there compatible replacements?
 

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I have a guy that will prolly havem. I got my motor from him. Great guy, reasonable prices.

His name is Cole. he owns larsenmotorcycles.com

484-678-9396
 

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If I'm correct the pulse generators are connected together and to a single harness that is sold together, but the good news is that they are used on a few bikes:

1983 VT500C A
1983 VT500FT A
1984 VT500C A
1984 VT500C AC
1984 VT500FT A
1984 VT500FT AC
1985 VT500C A
1985 VT500C AC
1986 VT500C A
1986 VT500C AC
 

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check wiring first, especially where the wire goes INTO the case.
 

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Discussion Starter #6
Cool ill be tearing into the right cover soon, but before I do, is there a another connector before it joins together going into the cdi box?
 

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it plugs into the cdi harness and runs straight into the side engine cover and slpits into 2. There is no "in the middle of the harness connection" just trace it back to the cdi and you'll see what i mean.
 

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Discussion Starter #8
So I have the whole right side disassembled, how do I test for certain the pulse generator is bad?
 

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Discussion Starter #9
I was able to test the pulse generators, they are both putting out ~400 ohms, how do I test the cdi box?
 

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Discussion Starter #10
I swapped the coils to check, one has a crack but ohms out fine, swapping them.front and back made no.difference.
 

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Discussion Starter #11
I ripped the cdi apart and found discoloration and corrosion on one of the chips. What is the compatibility for this bike? It has a single cdi box with 2 connectors coming out.

Numbers are 131100-4500
 

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Well there is no way to test the cdi box other than eliminating the coils and generators from the equation (as per manual). If the coils were both testing good and had no cracks then I would tell you to test the generators, wich you did.

Then at that point the cdi would be the culprit. But here's the thing, My one coil was cracked and still tested fine. Yes, very weird but very true.

I didn't swap it to check if the problem moved, I just got another coil.

So my advise to you is to get another coil or swap them both out to dynatech 2.2 ohm coils.
 

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Discussion Starter #13
The only cdi I was able to find wanted $200! Is there anyone out there likely to be parting one out that has one? I found out 83-84 has a different setup than 85, could I rewire this one to be retrofitted? Seems like all the wires are the same, but is managed by 2 boxes instead of one and I just have to move wires between connectors.
 

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I swapped the coils to check, one has a crack but ohms out fine, swapping them.front and back made no.difference.
Ok I just saw this. Prolly is ur cdi, but if your coil is cracked its on its way out..fyi.

go here....

Electronic for motorbikes - IgniTech P?elou? I think they are 180 bucks for a new one.

I don't think 83-84 can be retro fitted to work, but i'm not 100% on that.
 

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aw man I was saving the coils/wires/CDI/pulser from a 85 VT500

i was sitting on it for years and finally threw it out the other day while cleaning up thinking id never need it or find someone who needed it.....

dumb me. sorry
 

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I have seen them occasionally fail, the pulsers sit in hot oil in the motor and the CDI boxes are made with 1980s manufacturing process. they were only designed to last 10 years at the most and they are well beyond that now.

common pulser failures in the DOHC CB900s, GL1100s, and GL1200s, as well as CDI box failures..

I know there is a company reproducing modern boxes but i cant recall the name, we used some on bikes with great success.

better to get a new part than another original 1980s part
 

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I know there is a company reproducing modern boxes but i cant recall the name, we used some on bikes with great success.
Look at my responce before this one. I gave a link to the comp. that does it.;)

Also the problem with the 80s cdi's was that they were not eco-bonded. Meaning not very moisture or weather resistant.

The guys i linked to bond their cdi boxes.
 

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Discussion Starter #18
aw man I was saving the coils/wires/CDI/pulser from a 85 VT500

i was sitting on it for years and finally threw it out the other day while cleaning up thinking id never need it or find someone who needed it.....

dumb me. sorry
ah that really figures, it had this problem last fall and i put off working on it until the weather started getting nicer, i guess i should have torn into it much earlier huh? :roll:

i managed to find an 86 being parted out at a shop for $100, how likely is this one to be compatible? are the 85's a one year only ignition or did they use it in 86 as well?
 

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Discussion Starter #20
no one is listing a cdi box on ebay for a reasonable price, double what chop shops normally sell them for. can i get the 83-84 cdi boxes and splice the connectors appropriately? they seem to have the same color wires, and ill just have to combine a few of them. it seems to be a pretty simple system being: pulse generator > cdi > coil > plug.

any reason this cannot be done?
 
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