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Discussion Starter #1
Sorry to drag up this old problem again but jnr is still having problems with his 1980 Yamaha DT 125 LC3 Model 35E.
I followed up the leads suggested in the other thread I started but nobody had or could make a CDI for this bike...One guy offered to make one but he said it would cost a couple of grand.
Okay.
I need to know how I can locate the original part number of this bikes CDI from a Yamaha microfiche.
We have replaced the coil with a genuine one ,the flywheel rotor WAS burned out and was replaced with a second hand one and it was tested as working.
The bike starts but wont rev up so I am now convinced 101% it is the CDI.
This bike is doing my head in and sent my blood pressure so high that I am now on medication for it...:D:D:D
Where can I find the part number so Ican find a CDI?
 

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Discussion Starter #5 (Edited)
101% is pretty confident but are you sure?
Not certain enough to pay 400 euros but its not me that has to pay it.:D:D:D
I think when jnr comes back from walking the dog he is going to s hit his pants when he sees the price but I have been on this merry go round for a few months and I am so dizzy from it.
The only other progress i made was if I did a parts search omitting the first three digits of the part number which came up with yamaha offroad quads but they only have 5 wires and jnrs has 7.
So basically Jnr has to pay or sell the bike for spares but there is no way he will do that.
That I am 101% sure of..:thumbup:
 

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Discussion Starter #9
This is the only one i can see resembling yours also mentions the numbers on yours might be worth a message

CDI Unit DT125 Yamaha

T
his is yours save you looking for it
View attachment 109273
Thanks for the heads up , my heart jumped in my mouth when I saw the photo as I didnt realise it was the photo I posted in the other thread.:toothy3::toothy3::toothy3:
I tried calling them but the phone number didnt ring but it looks like what we are after.
I have sent them an e-mail to make sure its the right model..
I hope this pans out as I have just had a chat with jnr informing him that I am running out of ideas and he might want to start thinking about breaking the bike for parts if we cant find a CDI.:(:(:(
Fingers crossed.
 

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Discussion Starter #10
This is the only one i can see resembling yours also mentions the numbers on yours might be worth a message

CDI Unit DT125 Yamaha

T
his is yours save you looking for it
View attachment 109273
I just talked to the guy and sent him an e-mail with all the details and numbers so fingers crossed we have the right one.
Jnr will get creamed on postage ,vat and import duty but I reckon £200 more is better han selling his bike for spares....

Jnr owes you one mate.:thumbup:
 

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I was thinking immediatly the carb might need a clean with it standing still for a long time which me and jnr are going to look at today.
The fuel line has a filter on it to stop crud getting into the carb and that got me thinking it might be the CDi packing in.
Have you stripped and thoroughly cleaned the carb internals? - as a fuel filter won't stop it gumming up from inactivity. Before you chase your tail and splash out cash. Just saying...
 

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Just what i was thinking its a lot of cash to be spending on a part that "might" be the problem, did they fit a power valve to that model if so have you checked the correct operation of it and are you sure the read valve is ok. By all means find out if the CDI is the right part for you but i would spend a bit more time going through stuff that doesn't cost before parting with the cash :thumbup:
 

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Discussion Starter #13
Jnr was on a work experience thing and took his carb apart and the shop owner showed him how to use the ultra sound machine ,the flywheel rotor was fried and replaced with a genuine part as was the coil so I have told jnr not to try and start his bike in case the dodgy CDI fries that one too.
We checked the YPVS servo is working and it is set up correctly....(according to jnr)
It has to be the CDI because we have checked everything else it could possibly be...
He put new carbon fibre reed valves in too to replace the originals.
I will tell him to put his original reeds back in tomorrow before we order the CDI.
If it turns out to be the problem I will string him up by the short and curlys.:D:D:D
 

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Discussion Starter #15 (Edited)
I have been up all night coz I couldnt sleep looking for a CDI.
I put a post up on Facebook on the Veteran Japanese Motor Cycle forum asking for one using the OEM part number and a bloke in Ireland sent me a link to this ebay item.

NEW YAMAHA DT125 DT SYSTEM CONTROL UNIT 57U-85830-M0 1986 1987 | eBay

Its not an exact numbers match but its close enough for me to be wanting to :wav:

Look at the title of the item on ebay ,no wonder I couldnt find the blighters, not what I had been searching for....duh!....;););)

There was also one the same from the states with the same number but that one will involve more postage and a longer wait and then import duty and vat on top....
When jnr wakes up in a couple of hours he is going to feel like Father Christmas came a second time.:thumbup:
 

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Discussion Starter #16
Another question for you lekky guru,s.
If you compare the photo of the ebay CDI against the photo that my son provided ,they are not the same connectors.
My sons current boss reckons if we get the one on ebay he can make it work on the bike ,is that a risk worth taking at £200 a pop.
Another bloke on the internet suggested that these old CDI,s can absorb moisture through the plastic and a mate of a mates sisters cousin said if you put it in an oven on a very low heat for 10 minutes it will remove the moisture and it MIGHT work...
I suggested to jnr to take the CDI off and let it sit on a warm radiator instead of baking it with his lunch time pizza.
What are your thoughts gentlemen before we splash out another £200 ? :toothy3::toothy3::toothy3:
I told him to put the standard reeds back in to double check he didnt put the new ones in the wrong way round.:thumbup:
 

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Dunno, too many iffs & buts for me to be spending £200 on something that might not fit or work on the bike, or for something that might or might not be the problem anyway.

Two strokes can be fickly things (from my very limited experience)

Is the compression ok, basic service items, if it's been stood I believe 2t's crank seals can perish so they don't run properly, has someone done some 'diy porting' (badly), timing out, poor fuel feed/carb float height/needle/jetting/air passages/pilot setting, electrics - good connections, resistance checks on the loom, decent battery & charging system ok when running, exhaust bunged/gummed up etc etc

I'd be checking & eliminating as many of the above as possible before spending hard earned, starting with getting everything as stock as possible inc fitting stock reed valves.

Sometimes you just have to admit defeat with these things to save your sanity ( and wallet...)
 

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What exactly are the symptoms of this poor running DT ?
I've been unlucky enough to have the CDI go tits up on a few different bikes - DR350, XR250, DT250 on all of them the symptoms were virtually the same, cutting out, backfiring, refusing to start, generally running like crap, i've not read of you having any problems along those lines,
does it smoke much or do you have to keep topping up the gearbox oil ? that would indicate the R/H crank seal was leaking, i had that go on my dt175 it made it run very sluggishly . L/H crank seal would suck air and it would rev its knackers off and then blow a hole in the piston, that was my experience anyway
 

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Discussion Starter #19 (Edited)
Dunno

Sometimes you just have to admit defeat with these things to save your sanity ( and wallet...)
Who are you calling sane.:D:D:D
We took this bike for a blast in the Indian summer we had last year and the bike rode perfect.
Then Autumn and the rain arrived and the bike stood a while outside under a bike cover while it pissed it down.
We took another ride on it in November and the electrics died and I speculated that moisture might have gotten in the CDI.
This blew out the alternator thingy by burning out two of the pick up coils so this was replaced with an OEM part..
Someone on the interweb suggested that moisture can soak through these old plastic CDI cases and maybe drying it out in a warm room for 24 hours will sort it out.
I suggested to Jnr to put the CDI in a bag of dried rice for 24 hours in a warm room to see if the moisture can be soaked out and into the rice like a mate of mine did when he took his iphone swimming and it worked on his phone so it might just work on the CDI.
I would imagine the crank seals may be hard and causing a problem so thats gonna be an engine out and total strip down and refurb.
I just found a new old stock CDI in Europe for £100 so jnr is going to get it to see.
Jnr just told me he tested the lekky going into his battery and it was 16 volts so that made me think the rectifier/voltage regulator might be Donald Ducked.
I will include the video of jnrs bike when he sends me a link.:thumbup:


Jnr is learning that you need deep pockets to renovate old bikes but its what he wants to do.;););)
 

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Jnr just told me he tested the lekky going into his battery and it was 16 volts so that made me think the rectifier/voltage regulator might be Donald Ducked.
Definately too much leccy juice from R/R, which could well be damaging battery / CDI and other electronics. Add to the shopping list a new R/R & battery, along with CDI.
 
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