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beanmop

Bringing a YZ400F Back From the Dead

33 posts in this topic

I just recently scored a CA Plated 1998 YZ400F for $1,000 as a first bike. Sounds too good to be true because it is. I've ridden quads all my life, but after trying a YZ250 and a YZ450F on for size, I realized 4 wheels were dumb and that 4 strokes are the best. The motor started knocking, so the previous owner decided to stop riding it then and there and do a complete tear down and rebuild. I do mean complete rebuild too, not a single single bearing, gasket or seal was unexamined or torn apart.

He purchased all new gaskets, bearings, seals, and any other moving suspension/chassis part, as well as powder coated the frame. Then he got bored, bought a WR450 and left this one storage for a few years. It was never for sale, but I convinced him it would be unnecessary for him to have 3 bikes (he has a WR250F as well). Luckily he's a co-worker of mine, so any questions I have he's able to help me out with.

I definitely didn't completely know what I was getting myself into, but armed with a manual, some tools and knowledge from others. I'll see if I can pull this off.I'll be adding pictures as soon as they're taken, but because of monetary reasons, the bike will not be completed until I can afford to get the motor out of the local shop.

400F001.jpg

400F009.jpg

A very small portion of the boxes and boxes of parts.

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I got quite a bit of work done today, but regrettably, forgot to take pictures of most of the progress. One of the more awesome things about this buy was that all the new parts I've been installing came with the bike. I found a receipt with the cost of the parts, and it was about $800.00 wholesale (yup, not retail) of junk from White Bros.

The previous owner rebuilt the forks, while I checked out the Rear shock. I used 5wt Fox Oil in the forks and Rear shock. I've never heard it used before, but I figured that if it works well in full size Racing shocks, why not it in a motorcycle.

The manual basically said not the touch the rear shock absorber, but I've got quite a bit of experience with n2 shocks, so it wasn't all that crazy. The seals were fine and the valves in good shape, so I threw it back together and charged it up. The manual didn't specify, but with similar type shocks, I always use 200 PSI of N2, so thats what I did. If anyone knows better, please let me know! I'm used to reservoirs with floating pistons, so the bladder was a new one on me. Seems like a good way to save money on manufacturing though.

The Swing Arm, Pivot and Wheels all received new Bearings as well. (The steering bearings were redone by the previous owner a few months ago) The wheels were no problem, but the pivot bearing required a ridiculous amount of pressure to go in, as the bearing press read 7tons! I thought I was doing something horribly wrong, but the manual was followed completely and everything worked smoothly when done.

After doing the bearings and suspension, the easy part came. Putting the bike together into a rolling chassis.

400F004.jpg

The Newly Powder coated frame.

400F007.jpg

A Close up of the Color. A little shiny for my usual taste, But i really like the way it looks with the other colors of the bike.

400F005.jpg

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Rolling chassis, ready for brakes and electrical.

After I put the camera away, I did a little more work. The front Brakes got new pads(which came with the bike:ride: ) and were installed, as well as the front fender and fork protectors. More Pics and boring monologue on the way tomorrow!

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This sounds like fun. It will also be a great experience for you. You will know every part of this bike after this. Good luck and keep us informed of your progress.

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Thanks. Like I said, was way more than I expected. I got a lot done recently though, apparently just waiting for the moderator to approve the other post I put up last night.

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Looks like you got a sweet deal on a great old / new steed. Welcome to the club & keep us posted.

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Yes, they are retro back to the Black and Yellow days and they look great!! Your frame is a great color to go with them as well. Definately worth looking into!

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I've been looking for black plastics, I'll see what I can find. Thanks for the tip dude.

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I just had my shock rebuilt with Race Tech gold valves and I'm 99% sure they charged the shock to 150 lbs. I'll double check tomorrow and repost.

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Hey you should check you oil tank (frame) after that powder coating. You need to get all of the residue from power coating out. You might have already known that, just a friendly reminder.

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Ya, the oil tank has been flushed once already after the powder coating, but that was probably 2 years ago. I'm not sure what exactly to do, but I was planning on running brake fluid through it. Any better ideas? I've had to do quite a bit of sanding on the frame, as much of the tolerances were out of whack from the powder coating. The tap and die set had to be brought out as well.

This bike has Gold Valves in it as well. And as for the N2, I can't see how it'd make too much of a difference, but since I've got the capability to do it, might as well make it right.

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They will be yellow plastics with black decals. My personal favorite colors of all of the Yamaha colors out there. The kit is actually called a Hurricane Kit if you are searching for one, I don't remeber who made it. Hope this helps.

Josh

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Ya, the oil tank has been flushed once already after the powder coating, but that was probably 2 years ago. I'm not sure what exactly to do, but I was planning on running brake fluid through it. Any better ideas? I've had to do quite a bit of sanding on the frame, as much of the tolerances were out of whack from the powder coating. The tap and die set had to be brought out as well.

This bike has Gold Valves in it as well. And as for the N2, I can't see how it'd make too much of a difference, but since I've got the capability to do it, might as well make it right.

Here is some intersting reading. http://www.thumpertalk.com/forum/showthread.php?t=427495&highlight=powder+coating

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I just had my shock rebuilt with Race Tech gold valves and I'm 99% sure they charged the shock to 150 lbs. I'll double check tomorrow and repost.

Just checked with the guy that did my suspension. 175psi. Good luck, nice bike:thumbsup:

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After much neglect, the stars have finally aligned on this project. The Box of parts is now in a much more recognizable form, and hopefully in the correct configuration.

P1260006.jpg

I wasn't too confident in my own mechanical abilities, so I had the bottom end opened up and looked at by a well reputed local shop. The cam chain gear on one of the crankshaft halves was a little worn, so that got replaced. The Oil Pump was pretty scratched up, so in went a new one. Next, a new rod and bearings, the original reason this bike was taken apart and put into storage, were put in. Lastly, a new stock spec Wiseco Piston was placed in the recently Re-Nickasiled jug (I like Millenium Technologies.)

Before putting the head back on, a friend of mine helped me out with lapping the valves and setting them back in the heads. The valve compressor tool I got was terrible (probably better suited for an automotive motor). So instead one of us pushed down on our on the handmade tube-with-a-hole-in-it tool while the other set the keepers in place. We then put the motor in the bike, torqued down the head and set the cam timing.

P1260003.jpg

I'm hoping to get her running tomorrow, so more pics and updates then.

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Before putting the head back on, a friend of mine helped me out with lapping the valves and setting them back in the heads.

I've heard that you don't want to lap the valves in a modern thumper. Did your manual say to do it? I know that lapping the titanium valves can wear the coating off and cause the valves to require a lot more and frequent adjustments.

But you probably have the stainless steel valves. Don't know what, if any, heartache lapping those may have caused.

Hopefully I'm wrong. But the bike looks cool regardless.

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