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Our Blaster is not the run of the mill Blaster - any
more. This 1990 YFS200 is now sporting an engine which might
make this machine the perfect pick for our needs - a simple
lightweight machine that is reliable, has enough power, is
easy to start, gets good gas mileage and most importantly is
fun to drive. I fitted this Blaster with Yamaha's DT200
engine. It's essentially the Blaster engine though it's
liquid cooled and sports the YPVS power valve system. That
makes it a giant step up from the standard Blaster but not
quite the leap to a TRX250R. Yamaha rates the DT200 engine
at 31 hp. That, compared to the 17 hp the stock YFS200
engine puts out means it's very cool indeed.
- The oil injected DT200 dirt bike and YFS200 Blaster
engines share many parts with one another. The engine
cases are very close to identical - there's one
difference noted below. The crankshaft, piston and
associated parts are the same. The drive gear, clutch
driven ratio and transmission ratio's are different
between the two machines. The more powerful, lighter DT
motorcycle features a higher drive ratio to the clutch
and taller gear ratio's in the transmission as well. This
makes it interesting because depending on the intended
purpose of the machine, the driven ratio and/or
transmission ratio's can be swapped to help dial it in.
The top end is completely different because of the DT's
liquid cooling but the top will bolt on to the Blaster
cases without modification. Even though the Blaster
engine is air cooled it still shows its roots as
evidenced by the rubber plugs covering the coolant lines
that aren't needed on its generic water pump case. The DT
is equipped with a mechanical tachometer so its boss
shows on the upper right case too. Either version comes
oil injected but the DT version is variable. The
electrical system is also different between the two
models. The DT has a higher output stator that's used to
power its extra accessories and lights and is welcome on
the Blaster.
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- It's an easy and natural swap to the Blaster because
the motor mounts are in the same physical location and
bolt up with one modification. The upper rear engine
mount, a hole through the engine case, needs to be
enlarged to allow the Blaster's swing arm pivot bolt to
pass through it. That hole has a fairly hard washer that
fits into a recess on both sides of the engine. After
measuring the hole through the cases, the I.D., O.D. and
thickness of the washer I determined the best way to make
the parts fit was to use the washers that come with the
DT200 engine and modify them. I bored the hole in the
cases out using a 5/8" drill. I machined the washers to
the same size by chucking them in my lathe. I used a
boring bar to open up the hole. When done I tapped the
washers in the hole and inserted the swing arm bolt in it
to check the fit. It felt the same as the Blaster, so I
proceeded with the swap. The engine fit in the frame as
intended. All its bolts fit fine and assembled without
worry. The drive sprocket lined up perfectly, as did the
exhaust.
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- The electrical system of the DT200 has quite a few
not-needed-on-an-atv accessories that I quickly
discarded. The side stand warning switch, relay and light
were removed from the wire harness as were the pigtails
for the turn signals and the flasher hardware. The horn
and oil level switch were also removed. The wiring
harness was whittled down to the basic components - the
stator and flywheel, CDI, coil, regulator/rectifier,
power valve control box and servo motor. These components
were what was needed to run the engine. I was keeping the
full function of the power valve so a small 12 volt
battery would be added to the finished machine. I found
the battery fit well within the tool pouch cavity built
into the rear plastic if I made a small cut connecting
the two compartments. The power valve servo motor also
had to be mounted. Its two relatively short cables which
are used to open and close the power valve drum need a
fairly straight path to the right, top side of the upper
cylinder in order to function properly. I fabricated two
more small stays and welded them to one of the radiator
brackets. Though the position I ended up with was not
perfect it would do until I locate a couple of longer
cables to actuate the power valve. Two new power valve
cables about three inches longer each will allow me to
locate the servo motor in a better location protecting it
from water, dirt and debris. I spliced the wiring harness
to be able to connect the Blaster's handlebar kill switch
as well as the headlight switch. Its key switch will be
wired to turn on and off the battery but is not right
now.
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- Having a liquid cooled engine in the Blaster frame
meant adding a radiator as well. To cool the motor the
DT200 motorcycle was equipped with a single twin row
aluminum radiator measuring 5" x 10". I though long and
hard about the engine's new life in an ATV frame before I
settled on using two twin row aluminum radiators
measuring 5" x 9" each. These 1986 ATC250R radiators
seemed like the perfect parts to use because they are
used as original equipment on this bike and cool it well.
Fitting the radiators took some time because I had to rig
a way to hold them in place as I moved the suspension
through its movement and checked for interference. I used
small aluminum pieces to mock the parts up with. When the
final position was determined I fabricated the brackets
out of mild steel and welded them to the frame. They
would hold the radiators in place using three of the four
rubber isolated mounts the ATC used.
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- The Blaster OEM exhaust system works well but is
heavy so I replaced it with the FMF Fatty pipe the
machine had on it when I bought it. I capped it with an
FMF "Q" series spark arrestor / muffler. This "quiet"
series muffler would hopefully not only not intimidate
its young riders it wouldn't intimidate me when these
same riders are driving around and around the campsite
when us old folks are too tired to yell at them to keep
the noise down any more.
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- That's about it.
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- Just in case there was a serious mismatch in the
power characteristics of the new motor and its new
heavier-than-it-was-used-to home I brought with me a
stock Blaster crankshaft drive gear and its matching
clutch assembly. Along with those parts I also had a
complete Blaster transmission assembly. If the drive
ratio to the transmission seemed too tall I could change
just the crankshaft drive and clutch driven gear to the
stock Blaster components for a noteworthy change. If the
transmission ratio's were too far off I could change the
transmission to the Blaster OEM ratio's. By changing
none, one or both of these assemblies I had four
different combinations that would be sure to get me
closer to where I needed to be. In addition to that the
final drive ratio could also be changed to further dial
it in.
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- Other than me taking a couple of quick trips around
the block on it my kids were the ones running this
machine in on its maiden voyage. The "piped-only" engine
with its built in extra power proved to be an almost
ideal match for the DT's OEM gearing combination. Aside
from losing the kick starter in the sand on its second
tankful of gas the new engine / frame combination worked
flawlessly. Though we kiddingly blamed my daughter for
losing the part I knew it was my fault for not tightening
it properly because I was on the fence as to whether I
would use the Blaster's kick start lever or the one from
the DT. As it turned out I'm using a Blaster part due to
the amount of money I now have into the part ($90; at the
dunes price).
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- I took the machine for a long ride yesterday morning
to see if I could expose flaws that hadn't showed up yet.
For this outing at the Pismo dunes I picked four
different rides - the fence, grudge racing, Sand Highway
and sustained putting on the beach. The fence ride is a
fairly fast rolling-hill ride that takes as much
enthusiasm as it does energy in order to attack it's
bumpy, twisty, whooped out sections that bend from one
end of the popular sand attraction to the other. The
fence bobs and weaves through the sand creating many
rutted-out hard right and left hand turns as well as some
short steep mega-moguls and little sand hills. The
inclined drag racing area gives runs that appear to be
about 600 ft. to 700 ft.. It's groomed to be pretty
smooth thanks to a very enthusiastic person with great
ambition that keeps the action that much safer. Sand
Highway is a wide open throttle upper gears only assault
upon the machine's jetting and gearing, suspension, the
land and the body. Super slow driving along the
California coast line leaves time to take in the sights
of the many campers also enjoying this holiday
weekend.
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- The almost three hour tour shed new light upon the
situation. This combination is reliable, fast, powerful
and fun. For the first time aboard a Blaster the fence
ride was interesting and fun. Typically the Blaster would
run out of power just when ground speeds were becoming
entertaining. In the past this meant only cruising this
area of the dunes because a real attack on the coarse
aboard that machine was simply not possible. The power
valve YFSDT pulled from very low in the rev range and
revved to serious sweet sounds on top. At a power level
the stock Blaster knows it doesn't have, the new
combination had me thinking this must be what a TRX200R
would be like if there was one. Its top end pull, though
not worthy of true 250 class analogies certainly out
classed its YFS roots. Racing the incline turned few
heads from the onlookers on the sidelines because it
looks so much like a stock Blaster that almost no one
noticed anything different. There are a few riders out
there that probably thought they holed something or were
about to because they couldn't pull the "fake-out"
Blaster while racing. I won several races against a
probably-only-piped 1985 ATC250R with a teen ager
driving. These races had him pulling me out of the hole
by a bike to two, then had me pulling him through third
and fourth gears while revving out and ending in fifth a
full bike length ahead. Though these were very close over
all the ATC could not pull the YFSDT through the middle
or on top. I also won against a moderately modified
TRX250R with a heavy-ish rider driving. I would take this
machine by half a machine by mid-track then open up to a
full bike length by track end. The Honda 300 cc & 400
cc four strokes were no real match for this combination
though some of the noisier ones did have "it" paying
attention. The yellow Suzuki four strokes were everywhere
and were loud enough to be annoying. The beating beasts
jump out of the hole against the YFSDT and establish a
two to three bike length lead which they held the entire
distance. The YFSDT couldn't reel them in and they
couldn't pull it either. I can remember feeling that I
could easily launch harder to lessen their advantage but
I really just wanted to establish a baseline so I didn't
try any harder. The ride along Sand Highway was the
fastest and quickest I've ever ridden aboard a Blaster.
The machine never got away from me but did remind me a
couple of times it's a short machine. The almost-too-much
power-for-the-chassis feeling is its new personality, and
I like it. I pulled long drawn out high speed fourth and
fifth gear wheelies under full throttle conditions when
reaching for the edge of the racy combination. It's
power, weight and balance matched well to the fast
slow-rolling-dune terrain. I then idled through the
restless campers showing off their latest contraptions to
one another. The YFSDT didn't skip a beat when it was
asked to perform down low for an hour of less than
jogging pace shiftless putt-skooting.
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- I ran the gas tank real low a couple of times as did
another member of our crew. To be closer to ideal a
larger fuel capacity is in order. Adding things like
wider a-arms or a longer swing arm could make the machine
more like a TRX but in keeping with the Blaster tradition
those items are out for this project unless I decide to
go for a weight saving thing. My rear end hurt a lot
after the outing so a better seat would be good. No one
else complained about the staunch saddle so maybe it's
just my years showing. I can remember thinking about
better shocks while riding fast on the whooped out fence
ride too. These pieces, though pricey could find a home
here but I'll wait until others complain before I ante up
the dough. Aesthetically, a few things need to be cleaned
up. The radiator brackets need a little work - they don't
look finished enough. I'll spend some time on them so
they'll blend in smoothly. I need some shrouds for the
radiators too. I don't know if these are parts I can rob
from the same bike the radiators came from but I should
probably see if they're a possibility before I rule them
out. I need a rubber strap for the battery to prevent it
from moving around, but it's not a big deal. I should
probably swap out the six paddle Haulers for an eight
paddle pair but again it's not a big deal unless drag
racing is the order of the day. The liquid cooled power
valve engine is a little heavier than it's air cooled
sibling and the battery and other additional components
add to the heft. I'm guessing but I'd say the new machine
is 11 lb. to 14 lb. heavier than the old one. Replacing
the stock exhaust with the Fatty pipe saved a few pounds
as did swapping the OEM tires and wheels for the Douglas
.125's with the six paddle haulers.
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- Some time ago I had Ricky Stator rewind the original
Blaster engine stator for higher output lighting to be
able to light up the dual PIAA 35 watt driving lamps but
the DT comes standard with a lot more juice to the
lighting so additional work there was not done at this
time. The dual lights get to full bright when revving the
throttle just off idle so I'm guessing I could add more
in the lighting department when necessary. Thumbing
through the shop manual tells no clear output number for
the stator.
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- The primary, transmission and final drive
ratio's:
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YFS200
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DT200
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Primary Reduction
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71/22 (3.227)
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52/17 (3.058)
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1st
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34/11 (3.091)
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35/11 (3.181)
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2nd
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31/14 (2.214)
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30/16 (1.875)
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3rd
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25/15 (1.667)
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24/17 (1.411)
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4th
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20/16 (1.250)
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24/21 (1.142)
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5th
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19/18 (1.056)
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22/23 (0.956)
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6th
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19/21 (0.905)
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18/22 (0.818)
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Final Drive Ratio
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40/13 (3.077)
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41/13 (3.153)
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Vehicle Weight
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319 lb.
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228 lb.
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Ignition Timing
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16 BTDC @ 3000
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8 BTDC @ 1350
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30 BTDC @ 4000
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Bulb Wattage (12v)
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Headlight
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45w/45w x 1
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45w/40w x 1
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Tail/Brake Light
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3.4w x 1
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8w/27w x 1
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Oil Level Indicator
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3.4w x 1
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3.4w x 1
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Neutral Indicator
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3.4w x 1
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High Beam Indicator
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3.4w x 1
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Turn Indicator
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3.4w x 1
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Turn Signal Light
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27w x 4
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Meter Light
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3.4w x 2
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- Though I have a Digatron unit to install on this
machine I really didn't have time to set it up and dial
it in so I performed some plug chops to establish
jetting. It was incredibly easy to dial in. I started
with the jetting the Blaster had been running - it was
very close. I ended up setting the air screw 1 1/4 turns
out, a 25 pilot, clip set at the second position and a
240 main. The air box lid was on and there are no holes
drilled in it. This jetting was a little rich on top but
safe enough to let my kids ride it without worry.
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- I can now say without reservation that this is the
Blaster Yamaha should build. With few lightweight small
displacement machines available the YFSDT fits into a
well defined niche and would undoubtedly sell well, but
with two stroke things the way they are we'll likely
never see it.
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- * * * * * (Five Stars)
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- -Rick
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