Buying a new 2000/2001/2002 Yamaha YZ426 F
Volker Bartheld
Long time - no see!
I'm thinking of ditching my veteran 2-stroke CR 250 R (model 94) for a
brand sparkling new YZ 426 F since I can get a "last year" model for
little money.
My question deals with the model history of the blue thumper:
What were the mayor changes from the 2000-2001-2002 generation? Any
mayor illnesses? I don't need a 450 since I'm not into MX racing
business. Just enduro-fun riding, motocross in Italy and small races
(rarely). A lightweight, reliable and easy to handle 4-stroke is my
goal.
I already tested a 2001 model and found the cluth a little "rough".
Any insights?
Thanks a lot,
Volker
_
@: v b a r t h e l d @ g m x . d e * 3W: a c h i l l e s . g m x h o m e . d e
Volker Bartheld
On Tue, 25 Mar 2003 09:11:29 GMT, dr_ve...@freenet.de (Volker
Bartheld) wrote :
>What were the mayor changes from the 2000-2001-2002 generation?
I found the following in the internet:
> For 2001, Yamaha has taken its lightweight and powerful, five-valve,
> 426cc single and given it titanium valves. With the valves now more
> than forty percent lighter than last year's valves (and, remember,
> Yamaha has five of them in this head), the valve springs can be
> designed lighter and softer, allowing a quicker revving engine and
> improved throttle response.
>
> Yamaha also incorporates a new exhaust pipe (thankfully, allowing the
> oil filter to be removed without removing the exhaust header --
> something that was necessary on prior models), as well as revised
> carburetor settings. The carburetor changes were aimed at two
> gremlins, including (1) an off-idle stumble, and (2) difficult
> starting (particularly while hot).
>
> Changes to the frame material and rear swingarm material allowed
> weight reduction without sacrificing strength (in fact, Yamaha claims
> improved strength) and stiffness. The rear, aluminum subframe is 10mm
> lower for a flatter seating position.
>
> Changes to the forks and shock reduce friction, improve the
> "bottoming" feeling (and remove the "clank" heard by riders last
> year), as well as reduce unsprung weight in the rear. Aside from the
> titanium valves, the biggest news (shared by all other YZs, both
> four-stroke and two-stroke) is the revised front brake featuring an
> all new master cylinder and larger 250mm disc.
>
> The engine on the 2001 YZ426F clearly revs quicker than last year's
> model, and the stumble at the very low end of the rev range is gone.
> Power is also improved.
That leaves me with the question: Ist the off-idle stumble really that
annoying, do I need titanium valves and will I ever experience the
"bottoming" feeling, the (lame) way I ride. A difference of $700 between
the 2000 and 2001 model is really worth a thought. BTW, I can get a new
2000 for approx $4100.
Cheers,
Rowdy
> Any mayor illnesses?
The bike is okay, the Keihin is not. Beware of high mileage models:
The FCR carb has a flat side running on 4 plastic rollers within
the cast aluminum housing.
The slide consists of two parts:
- a frame that carries the rollers
- a thin plate suspended via a thin o-ring type piece of rubber
The rollers let the frame move before the engine side exit and take
all the air pressure difference. The plate is pressed gently and
independent of intake air pressure diff against the engine side opening,
thereby sealing the slide very well against false air.
Long time use of said carb (>5000 miles) will see the rollers dig
themselves shallow grooves into the aluminum carb body, thereby
bringing the frame closer to the engine side carb opening.
At some time this will result in the frame sitting tight on the
plate and having the pulsating air pressure hammer the plate
against the carb's housing causing the plate to crack.
Replacing the plate will _not_ give you another 5k miles of
piece of mind. The new plate will crack again very soon, as
it is not designed to see the full air pressure. been there
twice. Lucky people like me have not had the parts of the
cracked plate been ingested by the engine, poor slobs have...
This is especially dangerous for bikes that saw more off-road
and trail usage than MX where there is more idling and very low
throttle opening to be expected. (carb air pressure difference
=slide load is highest at idle)
This will happen to every Keihin FCR equipped bike, until
Keihin comes up with steel roller tracks or something similar.
btw. a new carb sells for around 1600 bucks over here...
HTH
Rowdy
PS: you can test a Keihin for old age:
With the slide at idle, stick your finger in from the air filter
side and press at the slide as hard as you can. You always should
hear the engine side plate rattle when gently tapped at from
the engine side opening. When the engine side of the slide appears
to be solidly stuck while pressing against the air filter side,
your carb is shot.
PPS: only bad people selling a separate carb would turn the idle
that low, that the rollers sit on normally unused real estate instead
of their worn out grooves thereby giving the impression of a perfect
slide with decent plate slack....
Jim Hall
>Volker Bartheld wrote:
>> Any mayor illnesses?
>
>The bike is okay, the Keihin is not. Beware of high mileage models:
I have a friend whose carb slide has gone through his engine twice.
He rebuilt the bike after the first failure, and sold it soon after.
Cherry looking bike. The slide broke on the new owner almost
immediately.
Frank took the bike back and refunded the buyer's money.
New carb body is over a grand here.
Jim Hall
520 EXC and others
turning Money into Noise...
vlj
<snip>
> Frank took the bike back and refunded the buyer's money.
<snip>
Now that is *class* ... wish the world had more of those folks in it.
Good ridin' to ya,
VLJ
--
Big air. Kids today, that's all they want, big air. I say keep it on the
dirt, that's where the fun is. You want big air kid? Pull my finger
-- Smooth Johnson (master of the berm)
SCCWSI
Bartheld) wrote:
>My question deals with the model history of the blue thumper:
The below concerns US models, there may be differences in Euro and/or
Canadian bikes that I'm not aware of...
2000- first year for the YZ to get the bigger bore to 426 cc. First
and second gear ratios are taller than '99, clutch added a plate, new,
redesigned Yamaha version of the Keihin FCR carb.
Illnesses: Grabby clutch, easily fixed with about $40 worth of '01
clutch parts. Also, the straight key used to retain counter balancer
drive gear would fail in some models resulting in engine noise and
possible case damage. Also sufferred a jetting glitch, use the '01
jet needle to fix this.
2001 - went to Ti valves, floating front rotor, Nissin MC. Front
brake much improved, clutch much improved, jetting much improved.
2002 - some minor changes to shock and swingarm I think, not much
else.
The cracking carb slide issue is a very rare occurence I think. This
was a problem with the 400, but I've not heard of this happening to
any 426 with the redesigned carb.
Other posts mentioned problems with slides in FCR carbs. I have not
heard of any problems in the CRF, KTM, and DRZ, all of which use the
FCR also, and have not heard of any problems on the 426 either. I
can't think of any modern four stroke that comes with a Mikuni.
Not buying a KTM RFS, CRF, or DRZ, especially a brand new one, because
of worries about the carb slide would be like giving up golf due to
fear of lightenting: irrational and unwarranted IMO. So I don't get
the paranoiia surrounding the FCR expressed in the other posts.
You can buy a brand new FCR from Sudco in the US for about $600.
Complete. With a few YZ400 parts this will bolt right up to a 426.
Hope this helps.
Rowdy
> Other posts mentioned problems with slides in FCR carbs. I have not
> heard of any problems in the CRF, KTM, and DRZ, all of which use the
> FCR also, and have not heard of any problems on the 426 either.
Maybe because only few of them got +25000 miles on their clock like mine?
> Not buying a KTM RFS, CRF, or DRZ, especially a brand new one,
> because of worries about the carb slide would be like giving up golf
> due to fear of lightenting: irrational and unwarranted IMO. So I don't
> get the paranoiia surrounding the FCR expressed in the other posts.
True for brand new ones. I (hopefully) will pick up my WR450F today.
But buying a Keihin bike with high milage is like wearing a McGarry
tinfoil hat while playing golf right underneath a thunderstom.
> You can buy a brand new FCR from Sudco in the US for about $600.
> Complete. With a few YZ400 parts this will bolt right up to a 426.
Thanks for that hint, but the buyer of my 25000 miles WR400F,
who was told about that carb thing by me years ago, decided he'll
still buy my bike and file down the grooves in the carb body by
hand. Bike still runs great now, except for enormous popping
when coasting.
YMMV
Rowdy