Question about Yamaha DT 125 R Motorcycles

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The sytem is pushing 35 volts not sure if it is the CDI box or the Megneto. can I fix it without buying parts.

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Check your voltage regulator

Posted on Mar 21, 2011


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Having a power surge problem on my atv...

This can usually be attributed to your regulator/rectifier. It takes the power sent via the stator - and forwards on to the charging sytem...kind of like an alternator regulator in a way. When shot - they can smoke your CDI, burn out lights, all kinds of issues. First thing - there will be a small box with fins on it, usually but not always on atvs with stators - you'll have 3 white or yellow wires coming out of crankcase - they go to your regulator/rectifier - disconnect that plug and make sure none of the wires have been pushed back or it's not caked full of dirt or mud. All looks good (and your sure your battery is in good shape - reply below with year, make & model - and I'll see if I can get you the proper testing specs. Testing them is really easy with any multi-meter; cheapest one they give you at Harbor Freight for spending $10 on Sunday will do. You'll want to pinpoint this and repair asap. A $30 rectifier can kill a $100-$300 CDI fast. All The Best & Good Luck

Aug 11, 2016 | ATVs

1 Answer

Hello, I have a 1997 Honda cbr900rr I have a 1998-99 cdi box in garage anyone know if it will work? Spent hrs online researching and nothing convincing

Hi, Trevor your 97 CDI and the 98-99 CDI are 2 different part numbers that being said they appear to be plug and play pretty sure you won't hurt anything, however, some systems may not function properly for this situation I would call my local dealer or reputable shop's service/parts department and inquire about any possible quick fix, answers, or parts inquiry. For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
1996 1998 Honda CBR900RR Fireblade Service Manual Moto Data Project
Honda CBR900RR Owner Manual

Btw, I’m available to help over the phone in case u need at

Jun 26, 2016 | Motorcycles

1 Answer

Cana elite 50 scooter run without CDI box

What is a CDI module? A typical CDI module consists of a small transformer, a charging circuit, a triggering circuit and a main capacitor. First, the system voltage is raised up to 400-600 Volts by a transformer inside the CDI module. Then, the electric current flows to the charging circuit, charging a capacitor. A rectifier inside the charging circuit prevents the capacitor from discharging before the ignition point. When the triggering circuit receives triggering signal, the triggering circuit stops charging the circuit, allowing the capacitor to discharge rapidly to the low inductance ignition coil, which increases the 400-600 V capacitor discharge to up to 40 kV at the secondary winding. This 40 kV then jumps the spark plug gap. When there is no triggering signal, the charging circuit is reconnected and starts charging the capacitor again.

Mar 25, 2015 | Motorcycles

1 Answer

Replace the cdi unit on a vespa lx 125 2005

Pretty straight forward, unbolting the cdi off the frame and replacing one wire at a time. Buying a service manual from say amazon for $20-25 bucks is the best investment you can make. It will offer other testing to be sure it's the cdi which is expensive, and be sure something isn't causing the cdi to burn out, once you take it out of the box it's yours, no returns on electrical parts.

Sep 27, 2014 | Motorcycles

1 Answer

Why is my 97 Honda 4 wheeler not getting fire

There are three items that are connected together needed to create spark on your 1997 Honda 4-wheeler, regardless of which model it is.
Before we go through a checklist of these three important parts, look for a black wire with a white stripe that runs to the ignition switch and kill button from the CDI box. Disconnect this wire before it gets to the ignition switch and kill button, then check for spark. The most likely cause is a broken kill switch on the handlebar, or shorted ignition switch. Such a condition grounds this wire and kills the spark.
If this test did not restore the spark, continue reading...
Here is what is required to create a spark.

First, the alternator has one coil which generates a high voltage--about 125 Volts AC for the CDI ignitor box.

Second, there is a pulse voltage generated once every revolution of the engine that goes to the CDI box. This pulse causes the CDI to dump its stored energy from the 125 volt line into the primary of the ignition coil.

Third, If the two connections of the wire that runs from the CDI to the Coil are BOTH SHINY clean, the ignition coil will generate a spark.

If any one of these 3 don't happen, the spark will go away. Of these three, item 3 -- one or two tarnished and/or dirty connectors -- is the most likely cause. Just an added resistance of 0.3 Ohms or more in the CDI to Coil connections will cause the ignition to fail. No other wires have to be this clean.

Sep 26, 2014 | Motorcycles

1 Answer

I have a 1985 honda shadow vt500c, and like many others before me, im in need of a cdi box, or a fix to a broken cdi box, the used ones on line are a bit pricey for my wallet.

Unfortunately, the ONLY thing you can do is replace the cdi box....what REALLY sucks is that those cdi boxes were only used by Honda for 2 years...85 & 86...all the other years/bikes had MUCH cheaper units on them...And DO NOT, I repeat DO NOT waste your time on a USED part that is 30 years old!!! There is NO WAY to test a cdi box!!! Bite the bullet & buy a NEW one if you want to fix it & forget it.....there are new ones available online from a company in the UK for about $259.00 I speak from personal experience with this EXACT issue & once you replace the cdi box, that bike will run (providing everything else is good)

Best of luck!


Jun 07, 2014 | 1985 Honda VT 500 C Shadow

1 Answer


The CDI box could be bad or the coil could be breaking down so maybe a new coil would fix you up they only run around 20$ cdi box on the other hand can cost an easy 100$ or better you might also try changing the oil but make sure to buy kinda thick oil cause it's cold out

Jan 13, 2014 | Suzuki KingQuad 400 ASi 4X4 ATVs

1 Answer

No spark, changed the coil, is there any way to test the cdi box without having to buy a new one.

There is a way to test a CDI box but you will have to take it to a shop that has the equipment to do this. I own a motorcycle/Atv repair shop and I don't own one cause they cost allot and I can't justify getting one.

Oct 16, 2009 | 2003 Yamaha YZ 450 F

1 Answer

No fire with I box on 01 katana

Make sure your battery volts while cranking is above 10.5 volts dc. Even if the bike sounds like it's cranking fine, if it's not above 10.5 while cranking the ignition system will not spark.

I’m happy to assist further over the phone at

Jun 23, 2009 | 2000 Harley Davidson XL Sportster 883

1 Answer

CR85R will not start

could be coil or cdi unit. take it to a dealer and have them tested. the fuel coming out the exhaust is happening because the engine is getting fuel and without spark, the fuel is not burning off. it has to go somewhere. and out the exhaust it will go. and it would be nice to find someone who has the same bike to swap out parts. much cheaper than a dealer...

Jun 03, 2009 | 2003 Honda CR 125 R

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