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FIREPLUG CDI for 1974~76 Yamaha DT400B/C, DT360A, MX400B, IT400C, YZ400C

  • shewelt
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4/26/2018: Just an update that we are going through some pre-production validation testing now. Have a few eval-CDI's running on bikes and another CDI headed out for testing later this week. We're at the mercy of the weather, so slowed down our progress.

However, we are moving again, and I expect to have feedback from the test-bikes shortly.

Hoping to have the CDI ready for the start of the season!

Thanks....Scott

For more info, here's a link for the FIREPLUG CDI WEBpage:
cdibox.com/product/fireplug-cdi-1975-76-...a-dt400-motorcycles/
26 Apr 2018 09:53 #1

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So far the test version fires, rides and runs. Hoping for some time this weekend to get more time with it. Very nice unit.

I’ll be reporting back as soon as I can!
IF it isn't one thing, it's another.
26 Apr 2018 11:47 #2

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We were trying to test out the prototype CDI box on my Suntank, and the bike would start but not stay running. Traded ignitions and there was no change. All the symptoms of a plugged carb.

Pulled the carb and CRAP I hate ethanol! So now that carb is in the carb soak for a couple of hours or so - maybe even overnight, but it’s the same old story. Clean your carb.

The weekend here has been super busy, so the testing is behind schedule - my apologies. I was hoping for a good result this afternoon, but it was not to be.

The good news is the new box works, seems to fire off a tad bit easier. Assuming the carb comes to the party, I am assuming we are very close to a workable solution!

Film at 11:00
IF it isn't one thing, it's another.
The following user(s) Liked this Post: Blackhat250
29 Apr 2018 18:02 #3

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Quite a bit of progress made on the project!

After a full carb strip, soaking to rid it of some ethanol goo, the carb is back on the bike, and a few other little gremlins were chased out. The bike was now running as usual with the full DEET rebuilt DT400 Stock CDI ignition. All is back to good with the world.

The Fireplug CDI box comes with proper color-matched wires and matching plugs to the original, so installation is plug and play. Mine of course is a customized harness so I had to do a few little extra, but on a stock system, it plugs right in. Instead of pulling out my original for the test, I simply added some handy dandy black tape to hold the box in a safe place while tests were done.

The bike started on the second kick. Quite easy and done standing on the right side of the bike with my left leg. I have some back/hip issues going on, so a normal off and on the bike is kinda painful. It does seem to lite off easier with the new box.



As you can see the bike starts easy and revs smoothly.



I was able to take the bike for about a 20 minute ride around our very hilly neighborhood and can say my seat-of-the-pants dyno says this thing works really well. Nice smooth advance curve - no surprises, just solid power throughout the rev range. I was in a fairly quiet neighborhood, so I didn't wrap it out WOT, but the system seems to work exactly as you would want it to.

The box I am testing is still a prototype, and after a few more days of riding, it will go back to the builder for potting (Epoxy sealing of the unit) and hopefully soon to be available for the public!
IF it isn't one thing, it's another.
The following user(s) Liked this Post: MarkT, Blackhat250, Snglsmkr, Taps
07 May 2018 23:57 #4

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So I now have several hours on the prototype CDI box from Shewelt (HewTech). As indicated above, this is a pure plug and play solution and I can now report we appear to have success!

I am using my DT2 SunTank 360 which runs a stock CD400 ignition. It actually is a DEET restore, so is as good as you get with a stocker.
The new box is noticeably easier to kick and starts easily. After warm it is an easy 1 kick affair.

It idles like a sewing machine and takes throttle at any RPM, accelerating uphill from about 1,800 in second gear! Very nice, predictable power band. No light switch! Consistent and smooth from idle to redline.

This one is still a prototype and is not water sealed. But I think we have us a winner!

I hope to get some more time on the bike this weekend, then I will be out of town for the week, but from what I can tell you right now, I am looking at a few of these for my own projects!
IF it isn't one thing, it's another.
The following user(s) Liked this Post: Snglsmkr
26 May 2018 16:08 #5

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