FZRSupport: the FZROnline Archive

Will the FZR600 4JH engine fit into a FZR400 1wg Frame?

If so, what mods are needed

It will fit. Do a search and you should come up with a couple of topics that address the minor adjustments to be made.

I tried a search before posting, put I must be using the wrong words and can't find any answers. Can anyone help?

Try looking for a YZF600 engine - the 4JH 'Foxeye' was badged as a YZF on this side of the pond, so that's what most of the how-to's around here are filed under.

IIRC, there's not actually much to mounting the engine; you'll need to read the notes on the carbs and the airbox.

A big gotcha is the TCI and trigger wheel - the 4JH wheel cannot be read by a 3HE or 1WG ignitor, and vice versa. To add insult to injury, the crank tapers are sufficiently different that you cannot mount a 3HE or 1WG flywheel on a 4JH engine. The end result is that a 4JH engine MUST use a 4JH TCI (or 4TV T'Cat). To further heap misery onto the project, the TCI connectors are completely different. The traditional solution has to either completely replace the harness (!), or cut away the connectors from both the donor and recipient harnesses and perform careful surgery.

A minor annoyance is the 'dancing tach', where the tach bounces from 0, to 4000, to the actual engine speed because there is no fuel sending unit attached to the appropriate TCI pin. The solution is to ground the fuel level pin through a 1k-ohm resistor.

I can supply an adaptor harness that will plug directly between the 1WG harness TCI plugs and the 4JH TCI; the fuel level resistor can either be buried in the adaptor, or - if you have / plan to get a YZF tank - I can include a lead that will connect to the level sensor in the tank. US$60 shipped.

4JH looms aren't big money over here and it's best to use the 4JH Foxeye CDI and carbs. The Thundercat has a TPS unit making the cab bank wider and T'Cat CDI looks for the signal.

Many thanks to everyone for the information, I have a better idea of where I'm going and what is required.

You need the downpipes too