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Uncle is working on a TRX300 FOURTRAX he bought. The CDI box has label with numbers: HC4A/ under those letters are the letters CI545A. He had a friend order a replacement but the new box is much smaller.

When that box was installed- motor would not crank and His wiring harness started melting in places.

The wires were repaired so we need to order a replacement.

Can someone either tell me if I can ohm out the box to test?

Uncle also mentioned- when he bought the 4 wheeler [a couple years ago] he had to tap on CDI box to get the engine to crank.

Any suggestions to help us would be appreciated!:smile2:


Super Moderator
3,342 Posts
1987 was the first year for the TRX300 and TRX300FW - there is no test for the CDI unit other than replacing with a known good unit.

The part you need is part number 30410-HC4-003 - it costs about $151 from Honda and the good news it is still available - it was only used on 1987 and 1988 model

There is a smaller box that looks nearly the same and I believe has the same plugs on it - it is the alarm unit - part number 38710-HC4-003 - costs about $163.05, but is no longer available

The alarm unit had 5 wires going to it - brown/red, black, dark green,pink and blue/red - the CDI unit had 6 wires - black/yellow, dark green, blue/yellow, yellow/white, blue/white and green/red

Make sure you have the CDI and the alarm connected to the right wires - the alarm had a relay in it to prevent the starter from working when in gear unless the parking brake lever was pulled in - it sounds like the alarm unit was the one that was being tapped on

Anyway, I have given you the pertinent information - good luck
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