Can I add an external cdi to my internal one?

GoldenMotor.com

Motakitty

Member
Feb 14, 2015
447
3
18
San Jose, ca
So I have 66cc China doll with the internal cdi. I'm wanting to convert to the external cdi. I did search but the one thread I found didn't really answer the question. I know how I would go about replacing the case, magneto, and cdi. But my question is can I use the stock internal magnet/magneto to power an external cdi? If so then how.
 

Davezilla

New Member
Mar 15, 2014
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You could check treatland to see if they got a magneto that would match up to the internal type rotor, these need to be a very close fit with a very minimal air gap for best results but if you can find a mag coil that would match up with that rotor it should work and you would probably end up with a lot more ignition power this way. You may need to by the matching rotor as well if you can find one that'll fit the crank.

The internal cdi's are becoming easier to find replacements for if you blew one on your engine if that's what you need and there are a few simple mods that'll keep them alive better, mainly just drilling a few holes in the cover and re routing how the air flows over the cdi unit. The stock cover and those small vent holes in this type cdi housing really don't let enough cooling air flow around the unit causing it to burn out too soon.
The basic mod to prevent the cdi from overheating is to drill a 3/8 to 1/2" hole in the cover right at the crank center, block off the small vent holes in the bottom of the cover and drill 4 or 5 3/16" holes in the front of the cover, this will let the small fan pull in fresh air and it can only escape after going over the internal cdi unit. The way it is stock, the little fan just swirls the same air around in there with no real way to pull in fresh air or move out the hot air.
 
Jan 17, 2015
591
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18
ca.
Hey guys, I've got a hs142 and the cdi after about 700 miles, just quit. Would you know if vent holes would help? I unscrewed the plug wire,freshened the end twisted it back on, nothing,new wire, nothing,what goes wrong with these cdi's?
 

Motakitty

Member
Feb 14, 2015
447
3
18
San Jose, ca
What about just making some sort of "hood scoop" for the cover to force outside air inside. I may have to try that. Still not even sure my cdi is the issue yet I still need to look at it. My motor might have been flooded.
 

Davezilla

New Member
Mar 15, 2014
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Definitely check your engine before shelling out $ for a new cdi unit... even tho this type is still only about $15, unless you want to have a spare just to keep on hand, which can be a good idea anyway...

You could probably make the cover into a "hood scoop" by opening up the front on each side of the bolt that holds it on. If you do this, you could remove the little fan blades off the rotor and drill a few small holes in back of this cover so air could flow in from the front and escape out the back of the cover. The fan may prevent fresh air from coming in if it wasn't disabled or removed using the "scoop"method.

The idea I came up with uses the fan to sucked air in from a hole in the cover and it'll force it out of a series of holes up front, the fan set up this way should easily be able to overpower the "ram air" even at 40mph and above since the fan will be able to pull in the fresh air from the hole right above the center of it, basically this would use the fan as a centrifugal air pump which would work at idle and become more effective as rpm increases but I needs somewhere for this fresh air to escape once sucked in, which is why the holes up front are needed, and also to direct the cooling air over the cdi unit.
I've seen someone using a billet cover on this type engine where they just cut slots between the fins for fresh air to enter and hot air to escape, this is another passive way to get some air circulation and because of the fins on the billet cover the slots cut between the fins are very inconspicuous, which could be good if building a custom engine....
 

Motakitty

Member
Feb 14, 2015
447
3
18
San Jose, ca
I know I'm gonna check the cdi before I do anything. After seeing the internal cdi vs the external ones, I like to think the magneto and external cdi would work better than the internal one. I think after checking the magnet clearance I'll pull the cdi check it and replace the plug wire while I have it out and clean the contacts.I may drill those holes too cause that does make allot more sense about the fan.
 
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Motakitty

Member
Feb 14, 2015
447
3
18
San Jose, ca
My cdi isn't my issue and I got a stronger spark using a sbp plug wire. But I'd still like to know if I can add something like a jaguar external cdi to my existing setup. Like can I piggy back off the stock internal cdi?
 

Davezilla

New Member
Mar 15, 2014
2,705
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San Antonio Texas
I wouldn't waste my money on the jaguar cdi... it retards the timing too much to the point it loses too much power, even set at the most aggressive timing curve, it comes in last place in every cdi shootout that's been done by members in here...
Here's a thread on several cdi units that have been rested along with honest results and reports... it seems funny that there are a whole lot of newbs in there with posts only in that thread, but results are results and they are consistent with the results of others who performed the same independent testing...
Dunno if you've seen this thread yet, but here it is in case you haven't... this should help you decide wheth e r to stay stock or not... http://motorbicycling.com/showthread.php?t=58455
 

Motakitty

Member
Feb 14, 2015
447
3
18
San Jose, ca
I haven't seen that thread yet but that's not the point of this thread. I have an internal cdi that I would like to upgrade but I don't see an upgraded internal cdi. So that's why I'm asking if an external cdi can be added to the existing cdi/magneto. I might just have to buy a stock internal cdi and open it up to see if it's possible.
 

Davezilla

New Member
Mar 15, 2014
2,705
10
0
San Antonio Texas
As for the possibility of putting an external cdi on these engines goes, I think your on the right track about getting a second unit to cut open and see if it's easily doable... you will need the mag coil from the original unit and if you can separate the mag coil from the cdi by opening it up, then it would be fairly easy to solder the mag output wires to a cdi unit and run an external.
The other alternative would be to see if treatland has a mag coil that'll match the diameter of the mag rotor then finding a way to mount it, by either hoping that it bolts right up (always best) or fab bing up a mount plate to fit it up, then you could use any external cdi available... definitely worth experimenting with.
 

Motakitty

Member
Feb 14, 2015
447
3
18
San Jose, ca
I've looked at treatland but didn't see anything that looked like it would work without allot of modification. I'm also wondering if it would even be worth it. I'm looking to get the hottest spark I can. I'm not looking to do this anytime soon but just seeing if it's possible or if anyone else has done it.