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I need help with brining my DT125 back to life, please do help...


BartekGo
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Okay, I was trying to be smart and being 16 I failed, I got an Yamaha DT125 and not sure what year it is however it's or was in decent condition before it got to me...

It was road legal but person before me used it for off roading only so he took all the lights off and switches but left the wiring, I decided to cut some of it and I failed horribly, I cut off most of the cables and now my engine wouldn't start no matter what I do, it does have a spark but it wont start :(

I do have a basic knowledge but not enough to fix this problem by my self and basically I want to have as little cables as it's possible, I want to have as little electronics as it's possible because than less electronics there is than less things there is to brake and fail.

So, I need to get my engine and only engine working, I don't need any lights or horn, I want as little electronics as it possible but I don't know which one's I need to get my engine working again and I would appreciate any help...

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1: hello might have been nice

2: is the bike a dtr, a dtmx or what? you didnt say

3: you have a spark so why do you think its an electrical issue?

...Paul

Sorry, I forgot :)

Hi, I'm not really sure what model it is other than DT125, when I got it, it didn't have any documentation or prove of what year it is but it is an Yamaha DT125 and I think that it's a recent one, How can I identify an year of production of DT125?

Because I cut off all the other cables other than one from magneto :rolleyes:

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allrighty, lets get this small little item out of the way first.

if you are getting spark. that means that the ONE thing that is responsible for igniting the fuel/air mixture is working like it should.

that being said, unless you arent getting air or fuel, or have a lack of cylinder compression. it should run. maybe not well if your fuel air mix is all wonky. but thats the only wire you need to make it run.

now, if its a newer bike with some sort of electronic powervalve or something that may be a different story. check on the frame near the forks, there should be some sort of label or badge that states year, model, etc.

anybody with more to know than I (which is quite a few of you out there) please feel to correct me if im wrong or am being misleading, as thats the last thing i want. my goal is to help.

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Under the seat, on the left hand frame strut, there should be a sticker with the model number on, failing that post the first 6 digits of your engine/frame number as that will get the model and year etc, if its a DT125R.

800-600.jpg

Vez.

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It does have an Power Valve and I will check the frame numbers later.

Engine was running 20 minutes before I decided to cut the cables off so fuel/air mixture and compression is good.

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1: hello might have been nice

2: is the bike a dtr, a dtmx or what? you didnt say

3: you have a spark so why do you think its an electrical issue?

...Paul

??

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I want as little electronics as it possible but I don't know which one's I need to get my engine working again and I would appreciate any help...

OOps, ripping all the wiring out will save nothing. The only electronics on a DT are the ones that make it run.

Battery, if its a PV, must have.

CDI, PV servo both must have's

All the flywheel gear, Gotta have it.

You will save having a couple of lights hanging off the bike. Thats all. :huh:

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Without the PV you can ditch all of the loom, but if you keep the PV it will need a custom one making up. Then there is the reed switch ( if it has one) etc.  Without the year and model its a guessing game.

Vez.

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There isn't any sticker on the frame however I got the engine serial:

*4bl-146224*

Will this help to identify my bike?

Its a DT125R, possibly a import, as far as im aware the UK bikes all start with *3MD* for the engine and frame numbers. So, it puts your bike anywhere in between 1999-2003. (in the 3RM9 model range)

Is the speedometer in KMp/h or Mp/h?

Have you cut the speedo wires? IF yes, what are you like with a soldering iron and terminals? :unsure:

Vez.

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Its a DT125R, possibly a import, as far as im aware the UK bikes all start with *3MD* for the engine and frame numbers. So, it puts your bike anywhere in between 1999-2003.  (in the 3RM9 model range)

Is the speedometer in KMp/h or Mp/h?

Have you cut the speedo wires? IF yes, what are you like with a soldering iron and terminals?   :unsure:

Vez.

Hmm very possible that it's an import, it doesn't have an speedometer as I already got it converted for off-roading only and I did cut the speedo wires and I'm quite good at soldering :)

So what do I have to do to get it working with as little cables as possible?

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Thats like mine ;)

Are you sure about that model label, Left hand side between the seat and side panel

like this

ModelNumber.jpg

Okay, I had another check and sticker is there but some one painted over it (me :lol: ) , all I can read out after scrubbing the paint off is A instead of B next to that black circle.

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Hmm very possible that it's an import, it doesn't have an speedometer as I already got it converted for off-roading only and I did cut the speedo wires and I'm quite good at soldering :)

So what do I have to do to get it working with as little cables as possible?

Well presuming that you have thrown the speedo out ( :rolleyes:) you will have trouble getting the bike to run without the reed switch that is in the speedo housing, probably not impossible, but it won't be easy.

You haven't made this at all easy with your " I'm a lumberjack and I'm ok" approach to cutting the bikes wires. I hope you learn from it!

Out of all the different DTR models, you have the one with the crap wiring diagram.

If you don't have a manual, get one. And then study the wiring diagram for the 3RM9 models.

I can list the components you will need, but this isn't a one post solution I'm afraid to say.

You will need: ( presuming your bike is a 3RM9 model)

CDI

Ignition Coil

Rectifier/Regulator

Battery ( with fuse).

CDI magneto ( flywheel generator)

Engine kill switch (ideally you want the ignition and kill switch, but you could just use the kill switch, but the modding wont be easy either way)

Power-Valve Servo

Reed Switch

The Cdi should connect up to the Flywheel generator, ignition coil and Power valve servo motor without any modification, just a basic connect the blocks. ( the cdi and ignition coil will require earthing)

The rectifier/regulator should connect to the flywheel generator and battery with minor modification to the wires. i.e adding terminals. ( the rectifier will need earthing)

The read switch needs to be connected to the cdi and power-valve servo and will be best soldered into the circuit.(i'm not aware of anybody successfully removing the reed switch).

The engine kill switch should be connected to the battery on one side and the rest of the power circuit on the other ( red from battery one side, cdi etc. on the other) you will have to customize this bit yourself.

If you struggle with any of the above, post some pictures and a good description of what you have done and i will try and help further.

Bear this in mind. When i first rebuilt a DTR (at about 13-14 y/o) the electrics gave me nightmares for days, but with perseverance it worked in the end. So don't give up if it gets a little taxing on the brain cells and takes a while to get it right.

HTH

Vez

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Yeh it wasn't a smart thing to do and every mistake I make is a new lesson...

So I need all the wiring? Because I would really prefer to drop all the electronics cause you really don't need them, I want it to be simple that if it brakes, I can fix it straight up.

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Yeh it wasn't a smart thing to do and every mistake I make is a new lesson...

So I need all the wiring? Because I would really prefer to drop all the electronics cause you really don't need them, I want it to be simple that if it brakes, I can fix it straight up.

You need to wire everything in the list in my previous post, most of the components listed have wires and connector blocks attached to them. So that is no wiring loom, but you will need wires, unless you know something i don't.

A DTR without any electrics at all is nothing more than a push bike without the pedals.

I'm not blessed with lots of patience, so please read the post again, thoroughly. :)

Vez.

EDIT: i don't mean to come across harshly, apologies if it seems that way. Your problem isn't straight forward or as easy as it would be if the bike was in front of me and i could see what you had done to the wires.

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