OZ ATV :: The Australian ATV Forum

[bansheerep]

i was lookin at buyin a 04 model yfz 450 and i was wanting to no if there is any problems that i should know of or any upgrades that i should do as soon as i get it and i wanted to know ur opinions on this model

[Postie]

1 st thing it must have billet case saver then it depends how far you want to go in your desired application.

Good bang for your buck, with plenty of goodies easily available,

PM Sicmic , he has a race strengthened 04/05 that would be good value, if you are still looking.

[bigjon]

Some info I gathered / collected over the years (I use to own an '04, which was a great quad. I like it so much I bought an '07).

There are a few areas on the YFZ450 that tend to start leaking. Thankfully, Yamaha has superceded some of the defective part numbers with better replacements. It is better to replace the parts before the leaks start, or more parts will get damaged in the process and need replacing (much of this information was obtained from YFZcentral & Bluetrax).

1. Water Pump Leak Symptoms:
How do you know that your Water Pump is leaking? There is a weep hole below the Water Pump that the coolant will leak out of. Usually it will leak rapidly, especially after the engine is shut off. DO NOT JUST PLUG UP THE HOLE! It is put there to keep the coolant from going into your oil.
If the weep hole under the water pump has not begun to leak yet, the preventative fix is cheap and easy. Just replace the one defective oil seal (#6 on the Water Pump microfiche). The original part number was 93102-11004-00, the NEW part that prevents this leak is 93102-11008-00 (runs about $4). The procedure to replace this one seal does NOT require the engine case side cover to be removed, just the coolant pump cover (this was taken from someone else on the other web site):
"order the new seal.. the one that goes on the impeller shaft.. then yes ya gott pop the hose off.. some fluid will drain.. unbolt the three bolts that hold the cover one... no need to change that $2 gasket o-ring as you said.. that’s not the problem.. remove the impeller by putting a socket on it with the bike in gear so it wont turn.. when it pops off use a flat screwdriver to pry out the old seal... coat the updated seal in lots of grease and use a socket of the same diameter to push it in evenly.. retighten the impeller.. than the cover, than the hose.. you can get the coolant full by just keep adding it to the overflow bottle start the eng and itll suck it in... takes like less than half a gallon total... process takes 20 minutes.. now that I’ve done it.. if it leaks again I could change in five minutes."

If you wait until you have a leak, you may also need to replace the following parts as well. Once the one seal is badly worn, the impeller shaft can get marred and it can damage the other seal and shaft bearing, requiring the engine side case to be removed to replace the parts.
93102-12106-00 Oil Seal (~$4)
93306-00105-00 Bearing (~$10)
5GR-12458-00-00 Pump Shaft (~$22)

2. Output Shaft Leak (oil leak around front sprocket)
Symptoms:
How do you know if your Output Shaft Seal is leaking? Just behind the shifter there will be oil running down the case. Usually when these go out they will leak quit a bit. Your skid plate will also have a good amount of oil on it.
The O-Ring on the output shaft has recently been updated from the original part number 93210-22164-00 to the new part number 93210-22298 (~$4). If there is no leak yet, you should be able to get away with replacing this single part. If you wait until it is leaking, then you may also need:
93102-32480-00 Oil Seal (~$7)
90387-2513F-00 Collar (~$11)
90215-21001-00 Lock Washer (~$3)

3. Decompression Plug (oil leak through plug hole from loss of plug)
Usually the stock decompression plug only pops out if you did the cam mod and/or you overfill the oil. It may be a good idea to replace it anyway as a preventative measure. When this plug blows out, your engine will start throwing oil out of the engine near the header pipe. The recommendation is to get the quasimoto racing decompression plug by Vibeguy (comes with the oil seal and an anodized aluminum plug) (~$16). The quasimoto decompression plug can be purchased at Thumpertalk and comes with Yamaha oil seal part number 93102-12224-00. The stock plug is black rubber with a circular aluminum disk built into the inner part of the plug. It is held in place only be the pressure on the sides. The anodized plug is held in place with a bolt that is already on the head of the YFZ whose sole purpose is to hold a decompression lever. First unscrew the decompression lever bolt (a little oil may leak out this bolt hole). To remove the stock plug, use a dremel tool with a drill bit so you can fit into the tight space and drill a hole through the stock rubber plug. It will be a little tough to drill because of the aluminum disk backing the seal. I usually screw in a dry wall screw inot the drilled hole so I have something to grab onto with pliers and then pull the plug out. Make sure to use a q-tip to remove any metal shavings that may have gotten into the decompression lever hole from drilling. Grease the oil seal on the inner ring and outer ring (do not fill the lip of the seal) and then put the decompression plug through the seal and then press the seal and plug into the decompression hole. Make certain the seal is flush and the plug and seal are pressed in all the way. Clean the oil off the decompression plug holding bolt and the hole it goes in, apply some blue loctite to this bolt and then tighten it in to the correct torque - DO NOT over tighten or you will strip the aluminum hole threads.
Also, it is always wise to inspect the engine mounts as it is fairly common to have these break (Engine Stay 2 and Engine Stay 3) and make sure they are not cracked.
Symptoms:
How Do you know if you need new front engine mounts? If you look at your 2 front lower engine mounts (they look like triangles with 3 bolt holes) there will be a large crack at either end.
The replacement parts for these are:
5TG-21316-00-00 Engine Stay 2 (~$7)
5TG-21317-00-00 Engine Stay 3 (~$7)

4. Battery Going Flat
The YFZ450 Charging System is designed to
supply at low to medium engine rpm a maximum
charging rate with the headlights in the
ON position. Under some conditions (e.g., low
speed with cooling fan running frequently or
continuous high rpm riding), it may be necessary
to ride with the headlights in the ON position
continuously to maintain a fully charged
battery.
If a customer complains of the battery discharging
while riding, first check the condition
of the battery.
NOTE: If improperly charged or boost charged,
these compact batteries could overheat and
become permanently damaged. To prevent
overheating, charge the battery using a low
output charger (e.g., Optimate III, ACCOPTIM-
AT-E3), and test the battery to make
sure it is in good condition. Next, Check the
output of the charging system.
To avoid mis-diagnosis, follow these procedures
and specifications in the order below:
1. Minimum key off (battery voltage must be
12.80 VDC).
• Voltage too low: recharge and load test
the battery.
2. Measure the battery voltage at idle. *It
should be 14.0 ~ 14.9 VDC before the cooling
fan starts to cycle ON and OFF.
• Voltage too low: check the stator coil
resistance. The correct specifications
are:
– Yellow to Ground = 0.22 ~ 0.60 ohms
– White to Ground = 0.29 ~ 0.84 ohms
– Out of Spec: replace stator assembly
• Voltage is too high: check wire continuity
(particularly the black wire which
should have continuity between the
Ground). The Yellow/Red wire should
have continuity between the lighting
coil and the regulator.
NOTE: If continuity checks good, replace the
regulator assembly. (Commonly, both headlights
are burned if the regulator has failed.)
• Voltage Okay:
–
–
–
NOTE: Do not check the battery voltage at
5000 rpm as explained in the Service Manual.
Charging output will decrease as rpm increases.
This is a normal characteristic of this
model.
*Since the system normally discharges anytime
the cooling fan is ON, all testing must be
done before the fan starts to cycle on and off.
Otherwise, the maximum measurable battery
voltage will be lower than 14.0 VDC.
SUBJECTS: 1. Unique Charging System Characteristics - YFZ450
2. Introducing YFZ450 Charging System Resistor Kit -
Resistor Kit for Competition Usage
3. YFZ450 Resistor Kit Installation Instructions

Check the radiator for blockage and
correct as required.
Advise the customer to use the key
switch to turn the engine off. Only
use the engine switch (on the handle
bar) in an emergency.
Advise the customer to switch the
headlights ON to increase the charging
output.
Introducing YFZ450 Charging System Resistor Kit -
Resistor Kit for Competition Usage
Symptom:
As explained in the previous subject (page 1),
the YFZ450 Charging System is designed to
supply at low to medium engine rpm a maximum
charging rate with the headlights
switched to the ON position. If the headlights
are removed for competition use, the unit may
experience battery discharging.
Remedy:
Install the YFZ450 Resistor Kit. The kit contains
a ceramic resistor which takes the place
of the headlights to maximize the charging
rate, plus it provides a higher temperature fan
thermoswitch to minimize current draw. The switch is
located sitting on the bike the upper right switch
NOTE: This higher temperature is still low
enough to not cause engine overheating.
The kit is optional for competition use and warranty
does not apply. The kit was developed to
allow maximum charging and reduce battery
load.
_________________
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