Z400J

[Kwackman]

My new toy, and my first project.
The photo flatters the bike, but it's a great start.
I had one back in the early 80s, loved it.
It's a Z400J, pretty certain it's a J3 model.

[kz900B1]

I like it look's every bit of a Z and comes in at the right price to get you biking

[Kwackman]

Yeah, thanks. I paid £750, and it was local rather than needing transported across the water which is never cheap. So, I'm pretty happy.
I bought this to get my hands dirty, and it looks like it's going to do that in spades.

Things discovered so far.
Oil leak, seems from around filter housing, but noticed the sump bolt wasn't tight- tried to tighten but it won't. So, I'm getting the sump off at least.
Headlight brackets are wrong, the gaiters were on the forks for a reason!, someone has painted a lot of bits with black hammerite, tail light is wrong, something ain't right under the seat where the air filter is, pretty sure the headers aren't tight to the head, at least no 3 isn't. But, it does run, and tickover.
The wiring is interesting in places too.
BUT, this is what I was after, a project, so I'm perversely looking forward to working on it.
I also managed to jam the ignition switch in "P" mode, so now I know how to get the ignition switch off the bike!

Tomorrow I'm picking up an important tool- a microfiche reader for £15, for the parts list I have which doesn't seem to be on-line anywhere.

[trikerdrew]

early gpz 550 barrels/head fit -instant oomph

drew

[nick pearce]

Good on yer mate, I had one back in 1985 ish and did some serious miles on it. Lc 's used to usually used to fly past but the 400J looked and sounded like a proper bike. Not many left in the UK now.

[Julian_Boolean]

I knew someone who had one that caught fire after he bypassed a fuse that kept blowing.

[Kwackman]

Ta, I did quite a few miles on my original J3 back in the day.
The wiring in this one is not inspiring, think I'm going to try to make up a new loom, what could possibly go wrong.....
I emptied the oil the other day, it was very thin and smelt of petrol which I'm told probably means a carb's float is not working.


Some photos..
Sump bolt- time for a new one?!

Wiring is interesting.

And what is this bracket below for? I know the grab rail is missing, but I don't think this has to do with it.

[Kwackman]

My Z400J project is at the taking apart stage.
I now know why the airbox didn't sit quite right, it was because the carbs were not OEM. Couldn't figure out why anyone would do that until I checked the engine number, and the engine isn't a Z400J engine! It had been changed a long time ago, and the "new" engine number is recorded on the V5.

After many hours of googling and microfiche searching, I've found that the engine is from a Z400F B2 model, (despite "F" being before "J" in the alphabet, the "F" model came out AFTER the "J"!) which explains the carbs, as they seem right for the F engine.

My ideal solution would be to find a Z400J engine, and I've put a wanted ad on the forum. I'm happy to be wrong, but I reckon I've very little chance of finding one.

But the engine from the F model fits in the frame OK, is similar in terms of power etc (although had a different bore/stroke ratio), and I can hopefully get the carbs to join the airbox properly. Other things that crop up- the Z engine had 2 throttle cables, the F has only 1 - The F has an electronic tacho, the J had a cable, so the Tachometer has been "fettled" to take the electric version - I'm not sure if the IC Igniter is the same for both engines. I think the airboxes for these bikes are different shapes because the F is a unitrak chassis whereas the J is twin shock

Trikerdrew mentioned in this thread that early GPZ 550 engines fit, maybe would be a better way to go, especially if the tacho was like the J engine, and the carbs fitted better. By early GPZ I'm guessing that means the twin shock versions?

Anyway, any advice or ideas would be welcome, and if you have a Z400J engine lying about you know who to call!

Cheers,
Davy

[LeeJackson]

Davy,

Are you planning to restore to standard? I'm assuming not since you mention a gpz550 engine? So why not just work around the motor you have? Else buy s 550 engine, A 400J motor would be worth it if your doing full Resto but not worth it otherwise I'd say?

Cheers
Lee

[Kwackman]

Thanks for the reply Lee.

I'd like to restore if it's feasible, if not as you suggest I'll try to work around the current engine.

I mentioned the 550 as trikerdrew put forward the idea earlier. If the 550 fitted straight in, I might consider it, and it might be as rare as a 400J engine!

But the dream would be to restore it as a Z400J.

Ta again for taking the time to reply.

[LeeJackson]

Davy

I'd reckon a 550 engine would be easy to find Vs a 400J? I have only come across one 400J personally, but lots of 550s.. Why not follow a period modified resto, then you can use what you have, bin the airbox for some filters and have some fun at the same time. Don't get me wrong I live a proper resto, done quite a few myself, but the costs can get scary.. Then you end up with something that cost 4 times its worth and won't want yo use it just my opinion.

Cheers
Lee

[Julian_Boolean]

Isn't a 400F engine exactly the same as a 400J engine?
GPZ550 engine will fit, both the 400s are under engined 550s, GPZ600R engine might fit as well, it's 550 based but water cooled.

[Kwackman]

Isn't a 400F engine exactly the same as a 400J engine?

No, they don't seem to be.
Apart from different carbs, the part numbers for the pistons are different, and also the cylinder block part numbers. The J has a mechanical tacho drive, the F electric. I THOUGHT the Bore x Stroke ratio was different, but looking tonight, I think I'm wrong and they are both 52 X 47mm.

I wonder if J carbs would fit the F engine? Hmm.

Been following your Z1000J project, Julian. Lovely looking bike.

[Kwackman]

I'd reckon a 550 engine would be easy to find Vs a 400J?

A few minutes on eBay and it looks like you are correct on that one!

Why not follow a period modified resto, then you can use what you have, bin the airbox for some filters and have some fun at the same time.

I don't like filters, but that's a good idea.

you end up with something that cost 4 times its worth and won't want yo use it

I'll try not to fall into that trap, but no promises! I have loads of time to waste on the project, but I'll not be going mad on the cash.

just my opinion.

It's appreciated!

[zed1015]

Had a 400J years ago.
All 400/4s are the same bore/stroke.
z500/550 engines (including the zr550 Zephyr) are based on the 400j and most parts are interchangeable within the crankcase.
The 500 is a bored and stroked 400 .
The 550 is a bored 500.
550 barrels fit the 500 (same stroke) but they are taller than the (shorter stroke) 400 so you can't simply drop a 500 or 550 block on the 400 for bigger capacity without loosing tons of compression.
You can make a rapid short stroke 500 by a fitting a skimmed (by 2.7mm iirc) 550 block on the 400 crank and case.
I think it was Performance bike or The biker magazine that built a Project 500/400 back in the mid eighties.