YZ400F?? Did I get got???

craigoctober · Jun 22, 2009

Hey everyone, Im new to the forum so this is my first post.

I bought a bike today for what I thought was a good deal for a 2003 YZ450F.
Turns out the cylinder says 399cm3.
So i gues its not a 2003 or a 450, so what im wondering is wether i can tell what year it is.
Is there a serial number i can look at to tell what year and model it really is?

also, seeing as I have been screwed over so far, what else should i be looking for? the bike needs plastics, where can I get these and what oother bikes are compatible.

I paid $680 bucks for the bike, and it seems like it needs a lot of love.

Also it needs an airfilter and cage, where should I look for these? can i buy them used?
Im without a job right now so im looking for a budget build!!

thanks

Craig

_JOE_ · Jun 23, 2009

No air filter?!!! :yikes:

Sounds like the opposite of a "budget build".

spark250 · Jun 23, 2009

unfortunately I think you bought the wrong bike for a budget build.

Most manuals will tell you in the front few pages where the model year identifiers are in the VIN.

$680 is a great deal, but if it needs the motor rebuilt you could be in for an easy grand depending on what it needs. And that would be considering that you could do the work....

Chili · Jun 23, 2009

First off you will need to identify exactly what you have, grab the 17 digit vin off the steering stem and enter it here http://www.analogx.com/contents/vinview.htm .

A complete set of plastic is likely going to run you about $120. All OEM parts will be the cheapest ordered from Service Powersports http://www.servicehonda.com/

craigoctober · Jun 23, 2009

Ok thanks for the advice!!! I have ordered some parts from the website you gave me so thanks for that!!
The bike is a 1999 model YZ400F.
I am going to clean up the carbs and see how well she runs after that.
It has a bobble at the bottom end and sometimes kicks out a backfire. The dealer said it could be the main jet, hopefully it wont be anything else!

Thanks for your help, ill update as things go to let you know how it turns out!

craigoctober · Jun 24, 2009

well i spent some time going through the carbs last night. seems like everything was clean and no jets were clogged.

I fired the bike up this morning, and it still has the bog when you try and open up the throttle.
when i easy the throwttle on it still seems like its not winding up like ti should, and im getting a backfire through the exhaust also that it quite bad.

any ideas?

Rich Rohrich · Jun 24, 2009

Did you pull apart the accelerator pump and clean the pump chamber? It fills with dirt and gets clogged making the pump pretty useless and that can make it bog.

craigoctober · Jun 24, 2009

how exactly does that work? im assuming that is the little upright hose on the carb at the bottom? i did clean that out and blow everything out of there.
is there anyway this could be a valve issue?

craigoctober · Jun 24, 2009

so i went and did some homework (remember i dont know anything about these bikes) and was looking at what and accelerator pump was because i wasnt too sure what you were talking about.
lookd up the diagrams, and it looks to me like something is missing... does anyone esle see what it is? first pick is the right side of the carb.

on the second pick, can someone tell me what that thing does and what should it be connected too.

on the first pick it looks like im missing and accelerato pump rod... is that right?

Rich Rohrich · Jun 24, 2009

craigoctober said:
on the first pick it looks like im missing and accelerato pump rod... is that right?

Yes, the AP rod is missing. That's the first thing to fix. ;)

The AP chamber is underneath that and has three screws that hold the chamber cover on. You can't blow it out to clean it, you have to disassemble it.

craigoctober · Jun 24, 2009

ok so i cleaned it out, and put in a rod so that it would work, but it just pisses fuel out from where the rod goes in, which i am assuming the diaphragm is ripped or became ripped.

where can i buy a rebuild kit for this carb? do i have to order it piece by piece or can i buy everything i need in one package?

any ideas on the backfiring issue?

dirt bike dave · Jun 24, 2009

craigoctober said:
any ideas on the backfiring issue?

Backfiring through the carb, or are you talking about a loud pop out the exhaust?

In any event, have you checked your valve clearances? Overly tight valves could be a factor. They tend tighten up with valve train wear.

holeshot · Jun 25, 2009

craigoctober said:
where can i buy a rebuild kit for this carb? do i have to order it piece by piece or can i buy everything i need in one package?

I'm not sure about "kits", but your bike isn't that old, so your local Yammie dealer should have parts for the the carb - maybe some parts will need to be ordered. In general, your bike isn't vintage yet, so parts should be easy to get.

Check the internet for microfiche files for your year and model - that way you'll be prepared before you go to talk to the parts guy. If you find the microfiche files on the net somewhere (yamaha sites or other), then it may be possible to order online.

craigoctober · Jun 25, 2009

dirt bike dave said:
Backfiring through the carb, or are you talking about a loud pop out the exhaust?

In any event, have you checked your valve clearances? Overly tight valves could be a factor. They tend tighten up with valve train wear.

Its coming through the exhaust. a loud po when it i rev it up and then let off the throttle.

How do i check the valve clearance? is it a big job if it is the valves?
could this be part of the bottom end bog issue?

Cabot · Jun 25, 2009

Once you get your Accelerator Pump (AP) working, your bog issue will be fixed (unless there is something else wrong). When you open the throttle, the AP rod gets pushed down, which pushes down a diaphragm located under the circular cover with the three screws on the bottom of your carb. This in turn forces gas through through passages and out a hole in your carb into your intake. Without this circuit, you will be running to lean off the bottom and have a drastic bog issue due to lack of gas. Theres a good chance that some crud is in your AP circuit, therefore causing it to fail, even after you replace your rod. Clean it out with some Carb cleaner and compressed air when you put that New Rod in! :cool:

Adjusting your valves is pretty easy, as long as you have a service manual and somewhat good mechanical skills. Anyone can learn!

Buying a service manual will be the best money you will ever spend on your bike!

Good Luck :ride:

dirt bike dave · Jun 25, 2009

X2 on the service manual. It might cost you $50 or more, but it will save you a lot of time and frustration.

FWIW, if your valves are too tight or not sealing well, it can cost you compression and low rpm power. Never had a YZ400, 426 or 450, but it would not surprise me if someone has posted info before on how to check the valves. Do a search for those models, and you will find some good info, I'm sure.

One of the big concerns on buying a used bike is the possibility that the valves and valve springs are shot. And if the maintenance was neglected for too long, you might need some head work, too.

sick 96 250 · Jun 25, 2009

Valves and everything mentioned is a good place to start after you fix the AP. Also if you are still getting that back fire try richening up the pilot jet some. At least from what I have learned a bog on decel is normally the pilot jet not supplying enough fuel.

craigoctober · Jun 26, 2009

thanks alot guys!!! the parts for the carb should be here on monday, and i will see if i can get hold of a service manual to check those valve clearances.
My brother says he knows a little bit about how to check that so hopefully i can get into this weekend and find out if that is within factory specs!

thanks for all the advice!! id be lost without it!! :cool:

ill update once i get everything taken care of!

YZ400F?? Did I get got???

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