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New to me '99 YZ400F. What to check?

11 posts in this topic

I am putting a call out to all the Blue thumper folks. I picked up a pretty clean '99 YZ400F that has all the stuff to set up for dirt (stock), Ice racing (stock rims, ice tires and fenders) or Supermoto (17" rims on stock hubs). It is my first Blue Bike so I need some guidance.

What are the weak links on the 400? What should I check during my tear down to grease everything and get to know the new toy?

Known mods.

12.5:1 Wiesco piston.

Hot start removed (can be put back)

Durelle Suspension (lowered 2" for SM & ice) with extra Stock Shock.

Polished and Ported Head.

DSP full Exhaust.

Ready to put on.

Got Zip-Ty fuel screw.

Got TM-Designs chain buffers & rollers to replace worn out stockers.

Got Tag T2 top clamp and Pro-Tapers ready to go.

I have read many pages of posts in the last few days, and I am going to check the Cam Chain, but other than that I do not see many problems with these bikes.

Any advice on what to check would be GREAT.

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I have that very same bike and I haven't had any major problems with it...or minor ones for that matter. Just the usual maintainence stuff.

Just a side note. How much did you pay for your bike if you don't mind me asking? I am getting ready to sell mine and i'm not sure what to ask for.

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I picked the bike up for $3600. Which might be a bit high until you realize the pickup full of stuff I got with it.

The list goes like this:

'99 YZ400

-Powder coated frame & swing arm

-Polished & Ported Head with 12.5:1 Wiesco Piston

-DSP full SS Race pipe.

Stock Wheels

17" SM wheels (Stock hubs, SS Buchman Spokes, Sun Rims)

Durelle Suspension lowered 2" w/ Eibach springs

Stock Springs

Extra Stock length shock

3 countershaft sprockets

4 rear sprockets

Stock Ft Brake

EBC Oversize Ft Brake

6 extra levers

Stock Piston w/ rings, wrist pin & clips

Extra Stock body work (except tank & shrowds)

Acerbis SM front Fender

Cut Stock fenders for Ice Racing

Custom Stainless Steel & plastic full coverage Ice fenders

Stock sized 21" & 19" Ice tires with screws

Good set of D755/756 moto tires

Michelin Pilot cut Slicks on the SM wheels with 90% rubber left.

And a few other odds & ends.

Kelly Blue Book lists a '99 YZ400F at $3100. I figured I could ebay off the extra stuff if I wanted to and make up the difference easy.

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The 400's are pretty durable bikes. Things I would check on any used bike are (not neccessarly in order)

1. condition of chain and sprockets

2. condition of brake pads and disks

3. Change coolant

4. change oil

5. change brake fluid

6. change fork oil (new fork seals maybe)

7. change shock oil and get it recharged with nitrogen.

8. Lube rear suspension linkage, shock eye's, and swingarm bearings

9. Lube steering stem bearings

10. Lube brake pedal pivot and kickstarter swivel.

11. lube the throttle and clutch cables.

12. Make sure shifter pinchbolt is tight (they do work loose)

13. Clean the air filter

14. Replace the oil filter (when changing the oil)

Then things that are yz400 specific

1. Check the valve clearances.

2. Check / replace cam chain. (if its never been done before just do it)

3. If its over 2 years on the piston replace rings. (ya gotta take the cylinder off anyways to replace the chain might as well do the rings while ya are in there)

4. Clean the carb and take note of what jets are in there. Watch the acellerator pump push rod boot. It can let junk into the pump. A little greese in that boot helps cure this.

Thats about all I can think of off the top of my head. Most of this is juse basic maintance and wont cost more than some greese and fluids. But seeing as its used and we/u dont know how/when it was last maintaned all this is good to go thru just for your piece of mind.

A top end and chain shouldn't set ya back much more than $100. Like I said if the cam chain has never been replaced then I would recomend doing it. You DONT want it to jump timing. That is wayyy bad. And the only way to replace the chain is to remove the cylinder / chain guides. So the rings are easy to replace at that point.

Dont forget to use the proper torque settings on the cam caps and lube the snot outta the cams when reinstalling. Bad bad things can happen if you slack on this step. Trust me I know. Dont overtighten the cam caps!

Hope some of this helps.

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May want to consider doing the James Now mod. You can find it here in a kajillion posts. This set the duration of the acc. pump so to speak. Very easy to do and worth the thime it takes to do it. Made a big differance in mine. Took all the bog right out. :thumbsup:

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A top end and chain shouldn't set ya back much more than $100. Like I said if the cam chain has never been replaced then I would recomend doing it. You DONT want it to jump timing. That is wayyy bad. [bold]And the only way to replace the chain is to remove the cylinder / chain guides.[/bold] So the rings are easy to replace at that point.

Negatory. You DO NOT even have to remove the head to install a new cam chain. I got one in without removing the head and only took me about 10 minutes at max.

All your information is exactly what I would say and I cannot stress enough.... REPLACE THE CAM CHAIN REPLACE THE CAM CHAIN REPLACE THE CAM CHAIN REPLACE THE CAM CHAIN!!!!!!

Jumping timing is NO FUN! Belive me ive experianced it!

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A top end and chain shouldn't set ya back much more than $100. Like I said if the cam chain has never been replaced then I would recomend doing it. You DONT want it to jump timing. That is wayyy bad. [bold]And the only way to replace the chain is to remove the cylinder / chain guides.[/bold] So the rings are easy to replace at that point.

Negatory. You DO NOT even have to remove the head to install a new cam chain. I got one in without removing the head and only took me about 10 minutes at max.

All your information is exactly what I would say and I cannot stress enough.... REPLACE THE CAM CHAIN REPLACE THE CAM CHAIN REPLACE THE CAM CHAIN REPLACE THE CAM CHAIN!!!!!!

Jumping timing is NO FUN! Belive me ive experianced it!

How did you get the chain past the chain guide that run next to the crank sprocket? There aint enough room to slide the chain past them. I even unbolted the back guide at the bottom and there still wasn't enough room. I ended up ....prying the chain past the guides. NOT the way to do it. To do it by the book I believe ya need to remove the head so you can get the guides outta the way. Then the chain has plenty of room by the crank sprocket to come out. At least that was my observation.

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It did come out that way. We unbolted the right side guide and moved it down a little, retracted the chain tensioner, pushed out the left side guide a bit, and with a long flat screwdriver and some rotating of the crank, we got it off. To get it on we put it on one side, rotated the crank and it went on easier then taking it off. It did take a few turns back and forth to make it perfectly on there. We got it on, and taking off the head wasnt an option.

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Thank you all for your input.

The YZ is currently on the opperating table and I am checking it over. I have already found a hole in the chain buffer and the chain guide is screwed. A set of TM Design works is on the way. I found the JB weld on the case (Grrr!) but it just looks like the bike threw a chain at some point. After chipping all the JB weld away the case was marred but not cracked at the clutch shaft infront of the countershaft sprocket. A new Case Saver is on order too.

Now I need to open up the top end and see what I find.

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It's a whole lot easier if you just pull the flywheel off... a puller only cost's $16.00..... and replacing the flywheel is a snap.

Bonzai :thumbsup:

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