Yamaha YZ400 1999 - First Project - Fix ride and Flip

[Samy J]

Hey Guys, 

I have just signed up to this site and learned a Ton from you guys. I just picked up a dirtbike that is either a Yamaha YZ400, year model is 1999. 

I picked up the bike for $1500 (AUS). The previous owner managed to kick it over but it was a struggle. None the less, decided to take it. 

It is hard to kick over, managed to get it running twice. 

 

Actions i have taken and plan to take:

Actions taken: Replaced the spark plug which was burned out, did spark test and it sparked.

 

Actions Planned:

The fuel petcock valve is leaking. Could this have an impact on starting and running?

Oil is low: Purchased oil and oil filter

Decompression cable threaded - Need to replace not activating consistently. Do you think the one below will fit?

https://www.mxstore.com.au/p/A1-Yamaha-YZ250F-YZ450F-WR250F-Decompression-Cable/51-273-80

The website claims it is compatible with 

Yamaha WR250F 2001

Yamaha WR250F 2002

Yamaha YZ250F 2001

Yamaha YZ250F 2002

Yamaha YZ250F 2003

Yamaha YZ250F 2004

Yamaha YZ426F 2000

Yamaha YZ426F 2001

Yamaha YZ426F 2002

Yamaha YZ450F 2003

Carb clean - clear the jets and re assemble.

Valvee Clearance and adjustment 

I have learned that once the clearance is above or below that tolerance, you will generally start noticing symptoms. Hard to start or backfiring are some of the most common. These are two common symptoms i am having when trying to kick it over ( Can skip leg day for two years already)

Air filter is filthy - Get a replacement and change it.

What other things can i do?. ( Beginner on the tools ) happy to learn and up for challenge. 

I am hoping the above should have it kicking over easier and solving the problem, however have been watching some videos on youtube on maintenence. 

We got it running twice. It goes good when running but backfires quite a bit also when kicking it over. 

Any tips tricks or resources will be appreciated. 

Cheers, 

Sam

Edited October 13, 2023 by Samy J

[cowboyona426]

Yes, the VIN will tell you which model year you have for sure.  I'm not sure if VIN's are the same in Australia and the US but you should be able to find a reference online to help you decode it.

A couple simple ways to tell if it's a 400 or a 426 are to check the cylinder, I believe on the left side of the bike.  There will be a casting indicating either 400cc or 426cc.  The carburetors are also different slightly, on the 400 the hot start was not directly attached to the carb and on the 426 it was.  Based on your photo, I'm guessing you have the 400.

[Samy J]

Thanks for your help@cowboyona426.

[donwann]

You need to add a valve clearance check and adjustment to your list.

[S.O.A.N.Z]

Frame and engine number ?

Check valve clearances

[Cirrux]

The carburetor can tell you what version it is as the year models had different Venturi's or sizing. Also the jetting that was it it could give you an idea. The wr400f 2000 had hot start with cold start. 

[Samy J]

10 hours ago, cowboyona426 said:

Yes, the VIN will tell you which model year you have for sure.  I'm not sure if VIN's are the same in Australia and the US but you should be able to find a reference online to help you decode it.

A couple simple ways to tell if it's a 400 or a 426 are to check the cylinder, I believe on the left side of the bike.  There will be a casting indicating either 400cc or 426cc.  The carburetors are also different slightly, on the 400 the hot start was not directly attached to the carb and on the 426 it was.  Based on your photo, I'm guessing you have the 400.

https://www.faxvin.com/vin-decoder

I used this website and it decoded the VIN. It's a 99 YZ 400. I come accross 400F models for the same year. Was it the same bike or different? 

2 hours ago, Cirrux said:

The carburetor can tell you what version it is as the year models had different Venturi's or sizing. Also the jetting that was it it could give you an idea. The wr400f 2000 had hot start with cold start. 

https://www.faxvin.com/vin-decoder

Found out decoding the VIN through this site. Thank's for your help bud. 

[Samy J]

4 hours ago, S.O.A.N.Z said:

Frame and engine number ?

Check valve clearances

Cheers my bro, will have a look. Found the model details with this site https://www.faxvin.com/vin-decoder

5 hours ago, donwann said:

You need to add a valve clearance check and adjustment to your list.

Thanks legend

[XRTrailRider1]

Just got a 99 400f as well here’s a link to a video of me starting it up after a carb clean. Is your bottom end this noisy? 
 

I also got an 06 250f in the trade and have that engine off to be completely rebuilt and it’s gonna be my baby because as you can see I’m a bit too short for this 400

[Samy J]

23 hours ago, XRTrailRider1 said:

Just got a 99 400f as well here’s a link to a video of me starting it up after a carb clean. Is your bottom end this noisy? 
 

I also got an 06 250f in the trade and have that engine off to be completely rebuilt and it’s gonna be my baby because as you can see I’m a bit too short for this 400

It does not have that rattle sound. I am unsure what that could be or if it is normal.  Mine needs work, does not kick over easy will check valve clearance. Will have a closer listen next time i get it going. Yeah, i am 6ft tall and barely on my toes haha. 

[cowboyona426]

On 10/12/2023 at 7:56 PM, Samy J said:

https://www.faxvin.com/vin-decoder

I used this website and it decoded the VIN. It's a 99 YZ 400. I come accross 400F models for the same year. Was it the same bike or different?

The F just stands for four stroke, some people/places use the F and others don't.

[Jimbob01]

The carb Is 99% this bikes problems 💯 get it working as the book says (with no air leaks) it’ll start every kick .. with or without a decomp leaver 👍🏻