Cheap CDI

GearNut · Jun 24, 2011

That style of CDI is not compatible with the HT system.

It is part of a typical 3 piece motorcycle system:

1. Stator with trigger coil.
2. CDI box.
3. Ignition coil.

HT engines do not have a trigger coil.

The trigger coil would send it's signal to pin #2 on the diagram that you shared with us.

skrew37 · Jun 24, 2011

Ok great. This is the kind of response I need. I know the ignition coil will work, but I bought the CDI on an impulse because of the price. It was half the price of a replacement stock CDI, so how could I pass it up? Now that being said, I would like to set up a better ignition system with timing advance and retard curves, etc. that will also smooth out the vibrations at high RPMs (Basically emulating/replicating Jaguar's system) because I'm getting shook apart at WOT. I would like to run at my top speed without fear of losing every nut and bolt on my bike. Is there a reliable (read "cheap") CDI that will work with our engines and the CR80 ignition coil that doesn't cost $75 for minor performance gains? Can this CDI I have in this thread be modified in a way that could work with the HT engines? I think research and development is key, and I very much appreciate the continued input. Help me guys!

socialdistortionkid · Jun 24, 2011

A new CDI wont change the vibrations its how well your engine is mounted.

skrew37 · Jun 24, 2011

I've read that it's best to mount the engine as solidly to the frame as possible. I slid a piece of innertube between the mounts and the frame. If this is causing the vibration, I'll remove them. It was said that if using rubber mounts, the studs can break. When I go to full throttle, I get a severe "buzzing" vibration in the handle bars to a point where I have to let off the throttle. I'm wondering if it could be another factor like the vibrations of the headlight and battery box assemblies. The upgraded CDI/coil combo is said to alleviate these vibrations at high RPMs. That is/was my goal for this whole project. I guess maybe I'll just have to live with cruising at 27mph when I know I can go, and have been, over 30mph. It just seems like something is going to "buzz" apart or the engine is going to explode when I get up to top speed. I know I'm new to this, but there has got to be some kind of happy medium for this "chinese super bicycle happy time" engine.

rohmell · Jun 24, 2011

Probably won't work very good at idle:

If you replaced ignition power with a battery, then would work better.

Ignition power= white wire
Ignition trigger pulse= blue wire

skrew37 · Jun 24, 2011

Thanks. I've seen that thread before, but haven't looked at it in a few days. I see Rohmel has made a few. I'm really interested in trying one out.

GearNut · Jun 24, 2011

The tricky part is the flywheel on a motorcycle has a separate magnet for the trigger coil, offset from the magnets that excite the alternator coils.
The trigger magnet position is precision timed to the crankshaft.

Usually the alternator magnets are on the inside diameter of the flywheel and the trigger magnet is on the outside of the flywheel. All coils involved are positioned respectively to the magnet positions.

skrew37 · Jun 24, 2011

Thank you for the diagram. Where would the black wire from the engine connect?

rohmell · Jun 24, 2011

skrew37 said:
Thank you for the diagram. Where would the black wire from the engine connect?

Black wire goes to ground

rohmell · Jun 24, 2011

Better schematic diagram, showing black wire:

skrew37 · Jun 24, 2011

Thank you. I checked the tracking stats and should be receiving both the ignition coil and cdi module today. I will try this set up first, post my results, and then attempt to make one of your cdi's.

skrew37 · Jun 24, 2011

What's the best gauge wire to use for this application?

rohmell · Jun 24, 2011

skrew37 said:
What's the best gauge wire to use for this application?

Of course, thicker is better, but use whatever is manageable, 16 gauge maybe?

GearNut · Jun 24, 2011

18 gauge will work fine too.

rohmell · Jun 26, 2011

skrew37 said:
Thank you. I checked the tracking stats and should be receiving both the ignition coil and cdi module today. I will try this set up first, post my results, and then attempt to make one of your cdi's.

Any updates on your ignition coil/cdi module?

skrew37 · Jun 27, 2011

Sorry, I was out of town all weekend. I received both the ignition coil and CID unit, but I haven't had a chance to connect it. I'll try to wire it up tonight, but I probably won't get an opportunity to fire it up until tomorrow (very quiet neighborhood at night). If it doesn't work, I'll trash it (CDI) and build my own.

rohmell · Jun 27, 2011

If it doesn't work, maybe you can open up the CDI somehow and see how it's wired inside, then we can figure out how to use it, or at least use its parts for a CDI of your own construction.

skrew37 · Jun 27, 2011

Good idea. But it looks to be filled with the same black epoxy as the stock CDI. Maybe I can chisel it out... but first I'll see if it works, of course.

rohmell · Jun 27, 2011

Yes, let's see if we can get it working, it would be great to have an alternative to the CDI that comes with the kits.

skrew37 · Jun 27, 2011

I agree. I wish 5pm would get here so I can leave work and make my way home.

Cheap CDI

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