How to install a CDI box?

5 replies to this topic
  • biggiefl

Posted August 01, 2008 - 08:27 AM


Friend gave me a red billet type CDI box for my 2000 XR50 and I have no clue as to how it connects....well I have a clue but I would like detailed instructions on how it connects. I have not tried to undo the stock unit until I know it just plugs n, etc...where is the best place to mount it? I have a BBR 88cc kit and T4 exhaust so it can't hurt to have more spark..or can it?

  • Mini-Outlaw

Posted August 01, 2008 - 06:29 PM


A CDI box removes or raises the rev limit on the motor,the stock CDI box has a set limit as to how high the motor revs & an aftermarket CDI either has no limit or a rather high limit.

A Honda has a wire from the harness with two seperate connection points plugged into the CDI box,like the stock Honda CDI box in this pic.

Posted Image

A Chinese CRF copy has a wire from the harness with only one connection point to the CDI box,like in this pic & is almost always on a longer wire not directly coming out of the CDI like the above pic.
Some aftermarket Honda CDI boxes have the longer wire connection point but they still have two seperate connection points not one.


You can use a Chinese CDI on a Honda or vice versa but you would need an adapter like in this pic,the two connection points would go into your Honda wire harness & the single connection into your Chinese CDI.
Or your two connection points into your Honda CDI box & the single connection point to your Chinese wire harness.

Posted Image

If you want more spark you need a race coil,which emits a better spark than a stock coil but then you should use a spark plug with the next higher heat rating with the race coil insted of your stock plug.
Just take your current plug into your local dealer & ask for the next higher heat rated plug,if it's a real CRF then your stock plug would have the rating on it & would probably be an NGK or Champion plug,very easy for them to look up & should be in stock for between $2 to $3 per plug.
Get more than one so you won't need one some day & have the luck to not be near a dealer or should it be closed you're bummed,you never know when you'll need the backup plug should yours foul or whatever but you don't wanna be stranded either.:ride:

Also it's usually best to re-mount the CDI where it was originally mounted on your bike,you can mount it elsewhere but where it's already mounted is the easiest place to re-mount a new one cuz you only have so much wire to play with unless you wanna dice-n-splice more wire to your system.;)

Here is my 07 CRF50 with an aftermarket Trail Bikes CDI,mounted where the stock one was under the seat,it's a tighter fit cuz it's bigger than the stock CDI but it dose fit.

Posted Image

  • biggiefl

Posted August 02, 2008 - 05:35 AM


Thansk..It's a TB and red just like above so now I know where it goes, etc.

My bike is a 2000 Xr50 in CRF clothing, no chinese on it except the Cheng Shin front tire.

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  • zach991

Posted January 05, 2011 - 07:18 PM


where can i get an adapter?

  • Towlieee

Posted January 10, 2011 - 04:03 PM


Thansk..It's a TB and red just like above so now I know where it goes, etc.

My bike is a 2000 Xr50 in CRF clothing, no chinese on it except the Cheng Shin front tire.

remove the plastic clips connecting the tank shroud plastic to the tank and the two screws hooking the plastic to the gas tank, then under the rear fender there are two 10mm bolts to remove, then you can slide the entire seat off, the seat has the rear fenders AND the front gas tank shrouds attached to it.

After that the CDI is on the subframe under the seat. Just remove the old, remove the plastic thing that holds it, and connect the new one.

I got my honda trail bikes cdi like 4 years ago, and if I remember right, there isn'y anyway to mount it.. I used like 3 zip ties to wrap around the cdi itself, then like 3-4 more to secure it to the subframe. Make sure you don't sit it on top of the motor or anything, when they get hot they can cut out!

  • Towlieee

Posted January 10, 2011 - 04:24 PM


also just FYI there aren't any performance benefits from an aftermarket CDI on the stock motor. It 'might' advance the ignition timing slightly, but you wont notice it at all.

And I'm not sure if the stock cdi has a rev limiter or not, but the stock motor wont hit it anyways, it falls off power, and the valves would start to float well before it would hit it.

However on a big bore motor I'd get one just for peace of mind

If your motor is stock, and you are wanting to stay SUPER CHEAP, a $99 88cc big bore is the best bang for the buck.. If you have the money, a stage 3 88cc kit from hondatrail bikes for $350, and it includes a crf70 style head that is ported, a 20mm carb to replace your stock 13mm carb, and a 88cc high comp jug/piston, also comes with a high volume oil pump and a CDI. It makes the bike a whole new beast, it adds soo much power, you go from around 2.5 horse power stock to around 7-7.5hp with this kit!

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