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Discussion Starter #1
I have been looking for the right z400 for a while. I wanted a chassis that hadn't been abused too bad, but didn't care about the motor, as I planned to add a big bore anyways. I found the z400 yesterday. It had low hours on it, but was ran in the sand dunes with a leaking air filter, wrecking the cylinder. Something happened and the head and cylinder were lost. The machine was also stored outside.... The motor is full of pine needles/rust.

The chassis is in real nice shape though. The stock plastic swingarm skidplate is still nice, as are the oem wheels. That is rare, for what I have seen while looking to buy a machine.

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Discussion Starter #2 (Edited)
I plan to tear the bottom end down and replace the bearings.
  • Add a 434cc cylinder/piston
  • fcr carb
  • Hiper beadlocks
  • Have Derisi (?) rebuild/revalve the shocks
  • Find a head with stock cams
  • IMS tank
If anybody has any of the parts that I need, or an opinion on my plans feel free to tell me.

My ultimate goal with this machine is to have something that I can race in the IATVHSS when I qualify for the +50 class (2022), and a decent trail machine.
 

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Discussion Starter #3
This is my 2017 RMX450z that I won my age group racing enduro. This is the best dirt bike I've ever owned! That is part of the reason that I want a Suzuki atv also...
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Stock cams will cost you some power, but will get around in the woods all right. Think I would at least do hotcams myself, but I'm greedy. :)
 

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Discussion Starter #5
Stock cams will cost you some power, but will get around in the woods all right. Think I would at least do hotcams myself, but I'm greedy. :)
I probably should do hotcams, but would like to use stock for now (if I can find some decent ones for cheap). I am trying to keep this low maintenence, so trying not to go down that rabbit hole...
 

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Discussion Starter #6
Drained the oil and water out of the motor and oil tank. I had to vacuum out the pine needles to fish the cam chain up out of the motor - zip tied it to the frame so that it would allow me to spin the motor over.

I poured a couple quarts of atf into the motor and spun the motor over through all gears. All seems ok, and none of the gears (that I can see) look rusty. There is a small area that is rusty on the crank, but I don't see rust anywhere else.

One thing that makes me wonder is that the big end of the rod does have some play. Seems odd that sand in the top end would cause that, and the machine doesn't appear to have enough hours on it for it to be regular wear. With the 'missing' top end, makes me wonder if it wasn't ran without oil or something instead? Who knows...
 

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That’s how I got my Z. Dude said the rings were bad and he had taken the top end off. After looking at it for a few seconds, I could tell the rod bearing had failed because it had the same play. Replaced the crank and the entire top end except cams. They had some scoring, but were salvageable.
 

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Discussion Starter #8
That’s how I got my Z. Dude said the rings were bad and he had taken the top end off. After looking at it for a few seconds, I could tell the rod bearing had failed because it had the same play. Replaced the crank and the entire top end except cams. They had some scoring, but were salvageable.
What crank did you put in yours? I used to buy pro x rod kits and have them installed by a local shop. Not sure if that's the best way to go, as I don't see pro x rod kits any longer.
 

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Hot Rods +4 stroker crank. I was very pleased with it.
 

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Discussion Starter #10
The local shop that used to rebuild crankshafts, no longer does it. I will get the Hot Rods +4 crank. I could have somebody else install the rod/bearing on the stock crank, but by the time you add shipping both ways and the hassle, it's just easier to order the new crank.

Hopefully it works ok with my planned other mods. I am only really after a bottom-to-mid range motor. The only time I ever hit the rev limiter is by accident... I learned many years ago that trying to make the z400 beat modded 450's out in the open is an expensive, high maintenance deal.

I do plan to run 22" rear/23" front tires. Maybe the extra tq of the longer stroke will help to move the heavy tires?
 

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Exactly. The +4 doesn’t need a special piston or any other changes. Never had any reliability issues. The +5, however, requires a stroker piston with a shorter skirt so the rod doesn’t hit it. Nothing wrong with having a little extra grunt. When paired with a big bore and an FCR39 carb, it’s got all the low-end grunt you’d ever want.
 

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Discussion Starter #12
This project is on hold for now.

I went to the dmv to get it registered, and while it hasn't been reported stolen or anything, the previous owner who registered it - his name doesn't match the bill of sale that I was given. It might take a while to sort that out. I learned long ago not to put any money into this stuff until you get the registration in your name...
 

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Likely bought and never registered it, destroyed the engine, then sold it again. Sad.
 
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