1980 GN400 Revival


New Member
Hey, guys. Switched gears and got a new project. I got this GN400 last summer after my uncle passed away. It was stored in a shed for about 36 years and I drug it out and am putting it back on the road.

What I’ve done so far:
Carb clean
Wheel bearings
Front brake system replaced

It started immediately after getting it home using starting fluid. Now it starts fairly easily and runs. But it constantly backfires and bogs down at low-mid rpms. It kind of breaks free at about 4K and will rev but backfires. This improved slightly after adjusting my float position. Lost spark a few weeks ago so I baked my CDI and regained spark. Today I adjusted the float again using a ruler to 23mm. Performance decreased.

So I know my CDI is suspect and my float height may or may not be correct. Can a CDI “kind of” work? Or is it an all or nothing? Anybody have any ideas?

Pics of rescue day and pic of two grown men on it for your entertainment.



New Member
I had a GN back in the 90s, and I'm still a big fan. Unfortunately most of their weird-alice CDI boxes are either completely kaput or are going bad. There is no aftermarket option and the OE boxes were long ago discontinued by Suzuki. It's really a bad situation. Either people will have to start retrofitting a completely different ignition system in its entirety, or there will be a lot of otherwise save-able bike going to the crusher.


New Member
It looks like I can find a OE CDI for $300 or so using the part number. Unfortunate, but maybe I better grab one.

As far as my issues, the next day the bike was running perfectly. Two rides later, still no issues. I’m happy, but also confused.

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