Sometimes I need more range than is supplied by the stock EXC tank plus my Baja
Designs side panel tank, which has been gradually disintegrating through various
mishaps and chain rub. The big Acerbis tank is really larger than I need, but
now, at least, I can carry enough to not sweat bullets on an epic ride. I'll
probably fill it to 3 or 4 gallons for most of my longer rides, with the extra
available for the occasional Hell Ride.
This tank is identical to the KTM Hard Parts tank. However, MSRP is US$250,
which is almost $200 less than the KTM version. I paid $225 (delivered free)
through Motosport.com in Portland OR. They were very quick and I received the
tank in two days via Fed-Ex Ground.
The tank is huge, as people have commented, but when I slipped it on my bike it
looked fine. It looks more like an adventure or Dakar bike and less like a woods
bike. No problem for me - I think it looks cool. I may not think that after
picking the bike up a few times....
Before removing my old tanks I topped them up to within an inch of the filler
and weighed the bike on a digital bathroom scale, front and rear. I then drained
all the fuel into an empty gas can. After installing the Acerbis tank I poured
that same amount of gas back in and again weighed the bike. Here's the
installation report. I've included some problem stuff I ran into that might be
of interest.
The small parts from the kit are at the center and
right, and the OEM petcock and forward seat mount are at the left. The original
front engine mount bolt lies under the longer Acerbis bolt for comparison.
Notice the difference in size between the Acerbis-supplied crossover petcock
(for the right side near the exhaust pipe), and the big clunky KTM petcock
(which goes far forward in the left wing).
First, install the two petcocks - don't forget the o-rings! - and then the two front rubber isolation mounts, using blue loctite on the upper studs. Slip the tank over the frame and onto the factory "rubber doughnut" frame mounts. This takes some wiggling. You can shine a flashlight up from near the left foot peg, past the choke knob to see the left mount to help guide the tank into place.
The two lower support brackets go on next. There are
two steel spacers that go between the brackets and the frame - the thin one goes
on the left side of the engine, as shown here (bevel facing out). Thread the new bolt
through the left bracket, spacer, frame, engine case and into the KTM frame nut
until snug. Don't torque it down yet. Notice how the upper bend doesn't align with
the bottom of the isolation mount. Why am I not surprised?
Carefully bend it using an adjustable wrench. The idea is to not pre-load the
rubber mount.
The right spacer is very wide and has a deep recess to clear the welded-on
engine mount nut.
Slip on the spacer, followed by the bracket and second nut.
Check and adjust the alignment of the top part of the bracket.
Install both front mount bolts and washers. Don't use
any loctite yet.
Check clearance around the radiators. The left side
is fine.....
Oops! It's kind of tight in there. The front of the tank sits a
little bit to the left, so it's hitting a couple of places here at the right
radiator. That is not good! I tried wiggling the tank around, but it wouldn't
budge over to the right, even a little.
The screwdriver points to two problem spots - the
rear corner of the top tank, and the top corner of the side plate. Carefully
reform the corner using a SOFT punch (I used a chunk of 0.5 inch nylon rod), and file and sand the point off the
corner.
And the rear edge of the side plate is really close,
and quite sharp. File and sand the lip off.
The lower hex head screw that holds the KTM electric fan in
place is hitting hard.
Replace the offending fan shroud screws with rounded sheet
metal screws, top and bottom to be safe.
The headlight mask hits pretty hard, since I long ago screwed
the fork stops way in to get some additional steering angle. Adjust them out
equally until the plastic clears the tank. Make sure they aren't bent, since
this is pretty common if you fall a lot, like me ;(
The Acerbis fuel hose is pretty wimpy - I am going to
locate some with a heavier wall thickness, similar to the formed OEM petcock hose. Routing is a
problem due to proximity of the exhaust pipe. I decided that the only good route was
straight across the top of the carb adapter. With a stout hose you could just
string it across. I decided to wrap the small hose with nylon Spiral Wrap to
give it some strength and abrasion resistance.
The hose in place, looped lightly over the carb
adapter.
This is the reason you should run the hose across the
top of the carb rather than under. Yes it might provide a small air pocket in
the hose to impede fuel flow, but this way you can lift a nearly empty tank off
the frame and prop it to one side to access the engine for a quick repair
without having to mess with disconnecting the crossover hose.
I was very concerned about the long, unsupported run
of hose from the left petcock to the carb, so I fabricated a support bracket and
mounted it to the lower rear water pump bolt. The piece is an aircraft 90 degree
"Adel clamp" bracket pounded open to about a 20 degree angle. You could easily
make one out of a scrap of heavy stainless steel. The white thing is a wire tie
clip for an electrical harness, again from an aircraft. It has two slots to hold
a medium sized nylon wire tie.
The Acerbis "Y" fuel fitting secured tightly to the
bracket, with a spilt section of fuel hose to act as a cushion. The OEM formed
hose remains on the carb, but it is rotated forward and up at the swivel
fitting. Note the very easy access to the choke and the two idle screws. This
took some messing around, but I am very happy with the result.
When you need to act as "tanker" simply squeeze the KTM spring clip with a pair
of pliers, remove the formed hose, and install a short length of fuel hose.
There is minimal fuel spilled and it is a really slick solution for transferring
fuel. This pic was taken earlier when I had not yet installed the cushioning
piece of split hose on the "Y". Without the split hose it wasn't very secure.
Detail of the left petcock, showing how horribly
vulnerable it is to trail damage. No wonder Acerbis doesn't show good pics of
this tank in the catalog! This is high on my To Do List. Can anyone point me to
a short petcock with Reserve? PLEASE?
UPDATE: 01/22/07:
With the help of the Husky fanatics at Thumpertalk, I
located a very close match for the small crossover petcock that came with the
tank. There is no Reserve, but I can live with that. The thumbwheel is a little
taller, but otherwise it looks identical. I really wanted a petcock with right
exit, but this one will work fine, though clearance is tight, as I will show
later. One advantage is that the pipe size is a much better match for the 1/4
inch/ 6 mm fuel hose wye fitting and the other petcock. The KTM pipe diameter is
a little too big. This petcock is a left side crossover petcock for a 2006
TE-610, P/N 8000-67440. Cost was $25 from MotoXotica in California
(1-707-446-4282).
The KTM petcock on the left, the Husky petcock on the
right. Also shown is the 8 mm x 1 inch long stud I mounted in the left rubber
tank mount, so I could use a regular nylon locknut rather than the exotic super-shorty
Acerbis mount bolt. The stud is on the right side is 3/4 inch long.
The petcock guard I came up with. It started out as a
piston from an aircraft accumulator (I can't recall what exactly - it's been 20
years) that I found in my scrap metal box. I lopped off most of the skirt and
drilled a hole in the exact center of the dome. It protects the new petcock very
nicely from all sides, and any impact from a fall will get transmitted directly
to the 8 mm mount stud and steel bracket rather than to the petcock and
vulnerable sheet metal screws. I couldn't figure out a lightweight, simple to
build design that wasn't circular in shape - anything asymmetrical will try to
pivot in a fall, so it would need additional braces or other stuff. This can
pivot all it wants - the load will still go where it should and the guard can't
be pushed out of alignment. I haven't studied a KTM axle slider up close, but I
suspect you could modify one of those to work here without too much trouble.
I was pretty worried about the radiators, but I
couldn't get my KTM steel guards to work, though others have reported success. I
just didn't have the clearance! So I installed a set of Bullet Proof Designs
radiator guards (CLICK ME). With the radiators
reinforced and really, really solid, I could use the outer edges of the
radiators to brace and center the tank. The standard way to do this seems to be
by installing a pair of MXC tank mounts, which are the exact same part as the
main mounts on the frame backbone, and also the center mount on top. The problem
is, they are US$10 each, which is about $9 more than they are worth, and since I
am always ready to accept a cheaper alternative to price gouging, I visited the
hardware store. Four rubber bumpers were US$3, and eight nylon glides were US$8.
One 1 inch OD nylon furniture glide is installed at
the very top and another 4 inches down on the side of each Bullet Proof guard.
They fit perfectly and go on easily using the supplied double sided tape.
There's a hole in the middle of each glide for a rivet or screw - if they don't
stay in place I will add stainless rivets. At the bottom threaded holes I
installed rubber furniture bumpers using the new 6 mm bolts from the kit - the
heads fit very nicely into the recess of the holes. They are a clone of the KTM
part but I don't expect they will last very long. I'm going to order a couple of
KTM mounts and keep them on hand for when they are needed.
Close up of the left side, showing how I shimmed the
lower rubber mount with a few flat washers to help stabilize the wing of the
tank. The other wing fits tight against the pads so shimming wasn't needed. With
these pads in place, the tank is much more solid and no longer wants to float
around when pushed on from the side.
The entire left fuel hose system.
UPDATE: 01/22/07:
The "revised" entire left fuel hose system, showing
the new smaller Husky petcock and "hockey puck" guard. I also tossed the wimpy
Acerbis fuel hoses and installed 1/4 inch automotive fuel hose and spring clamps
from NAPA. The hose is really close to the front bracket, but it does not
interfere. I installed a nylon tie at that point to keep it from chafing. The
hose is actually better protected from brush here than in the earlier setup -
the steel tank bracket will act as a very good deflector.... I hope!
I have a minor worry about adequate fuel flow thorough only one of these smaller petcocks at sustained high engine speeds, but with both open it shouldn't be an issue. I'm a slowpoke anyway.
Time to mount the seat, except that it won't go on!
The front mount stud seems to be too low. Shim it up as needed with a washer or
two, until the seat will "just" slide on.
Detail of the new and old engine mount bolts. Notice
that the unthreaded length is exactly equal on both bolts. This means that you
can safely torque down the Acerbis bolt without the front tank brackets in
place, and it won't bottom out. This is good news! We must, however, leave the
spacer under the head or it won't work.
This is what it looks like torqued down with no
bracket. That isn't too bad.... The small button head bolt is for the skid plate
bracket.
To make it possible to remove or install the left
bracket without pulling the bolt clean out of the case and frame, slot it as
shown. Dress down the sawed edges with a fine file. Now I can swap over to my
regular skinny tank for woods riding, in about five minutes, once I have bought
and installed a spare petcock and front seat mount into the old tank.
The left bracket in place, showing the slot. I forgot
to prime the cut area, but will do that some other time. When you are finished
fitting the tank, remove the lower bolt and apply silver anti-seize compound and
reassemble. Torque the bolt to 44 ft lbs. Then tighten the right bracket nut by
hand using a box end wrench. Access is not very good with a skid plate
installed, but it is possible. It's a "free running" nut, but it has locking
serrations under the built-in "washer" of the nut. Remove the two small front
mount bolts and reinstall with blue loctite. These appear to be oddball sized -
it would be a good idea to buy a couple of spares.
That completes the actual installation, but I wanted to do some fuel capacity tests. I poured the (approximate) 3.3 gallons drained from the two old tanks back into the new Acerbis tank and checked for leaks. I then weighed the bike on the bathroom scale to see what happened to the weight bias.
When I was done I leveled the bike on my race stand into a "riding" orientation, with the bottom of the frame at the same angle as when I am sitting on the bike. I drained fuel out with both petcocks open to see what the reserve and unusable fuel amounts were. This isn't completely valid, since there were no extra forces acting on the fuel, but it represents a worst case scenario, like droning down a straight and level road.
The top edge of the masking tape shows how much
unusable fuel remains on the right side. Most is caught up front in the wing,
but a little is back by the petcock.
Unusable fuel on the left side. The weird triangular
section behind the carb looks bad, but it actually traps very little fuel.
Not too bad! That is all that is trapped with the
bike in a riding position. It's a little less than 0.3 US gallon.
I leveled the bike left to right using a bubble level
held to the front fork. I dumped back in the unusable fuel and then added a
gallon at a time, waiting several minutes for the fuel level to equalize. I
marked each gallon on both wings. With a bright light you can see the fuel. It
isn't nearly as easy as with a natural tank, but it's better than guessing. And
the orange tank doesn't look like a huge dead slug draped across your bike....
Completely topped up the tank held right at 6.3 gallons, not including the
unusable amount. That is as advertised..
Now it has Really Big Ears. Time to replace that
ricketty side stand....
Yes, it is definitely wide! That will take some
getting used to. I don't think I will be attempting any tight single track with
this tank installed..
Some random observations:
The new tank weighs a little over 10 pounds including the stout steel mounting
brackets. The OEM tank with wings weighs about 5 pounds. The BD tank with
brackets weighs 3 pounds. The KTM tubular steel radiator guards which I removed,
since they aren't needed with the big tank, weigh 2.5 (!) pounds. Total removed
weight was 10.5 pounds. Net weight gain: ZERO. That is pleasing!
I will miss
that lost steering angle.... ;( If it's too bad I will trim the headlight mask and run the
stops back in.
The front left petcock looks really vulnerable - it hangs down a little below
the bracket. I don't know what I can do about that - maybe someone will suggest
a stout guard or a better petcock.... I don't know what Acerbis was thinking.
The weight bias (with about 3.3 gallons) shifted to the front tire by a factor
of 8 pounds, compared to using the rear Baja Designs tank. That is less than I expected, but it will be nice to have the front
tire weighted better for slick turns. With half a load of fuel, the weight is
carried lower and forward compared to the stock tank, so I expect the bike to feel different. It
will probably be harder to loft the front, but it should feel better in turns. I
hope.
I was worried about the amount of Reserve using the OEM petcock in the left wing
(the tank comes with an Acerbis screw type mini-petcock with no Reserve for the
right side, near the kick starter). No worries - Reserve is 0.85 US Gal. Maybe a
little high, but with a max range of 300 + miles, I think a 35-40 mile reserve
is about right.
Unusable fuel was a real surprise..... less than 0.3 US gal. I was really pleased with that
amount, since the OEM tank has about 0.5 US gal unusable trapped in the right
half of the tank, forcing you to wheelie or jump or lay the bike down. to splash
it across the frame hump.
Oh yeah, my Wolfman Enduro tank bag still fits fine. I had to loosen the front
strap a couple of inches. It sits a little bit higher in front.... that's the
only difference. Cool.
Ride Report:
I sneaked in a quick 6 mile ride around my neighborhood in between hailstorms, with about 4.5 gallons of gas. The bike feels top heavy and sluggish, and that will take some getting used to. I can't imagine riding on anything but smooth pavement with a full load! The width is visually startling when you glance down, but the tank is still narrow enough in back that it doesn't present any problems with moving around. I hope.
It's going to be interesting in the Spring. I'll make a full "Bad Road" test when I get some time under the new tank.
UPDATE: 01/22/07: "El Mur" from KTMTalk was a great help and with his permission I have added some of his email comments:
John: Great writeup on the tank - I found your info on the reserve vs unusable fuel to be especially helpful. When I installed my tank ('06 525 EXC), I did two additional things: 1 - I shimmed the small mounting ears (that attach to the frame under the tank) out a tad. This made installation quite a bit easier, and it actually increased clearance around the rads. 2 - I fabricated studs for the lower holes in the Acerbis-supplied rubber biscuits, and installed them with RED Loctite. This makes re-installation of the tank a breeze, and I used Nyloc nuts on the studs so that I don't need lock washers or Loctite when re-installing the tank. I have done one Baja on the tank, and I, also, was concerned with the stock petcock's apparent vulnerability, so I replaced it with a Husky (screw-type) tap. It seemed not to flow enough fuel, so I have reverted back to the stocker. I am off to Baja early Feb. - I'll see how I make out. These are my "hints", thanks for yours. Murray Dochstader - Kamloops, B.C. Canada.
__________
My tank sat slightly to the left (when looking down on it from the seat). I first shimmed the "ear" on that side, and the tank seemed to be better aligned. It was still a tad tough to slip off and on, and after a lot of time on my hands and knees, I decided to make some shims with my hole saw out of various thicknesses of alu. sheet. I am quite happy with the ease of fitment - I used one 1/16" approx. on each side. Another issue which did not show up at first, was the fact that I use "hard parts" (tubular) rad guards. The flat bracket near the bottom of them (to attach shrouds with the stock tank), were eating into the tank. Initially, I simply smothed them off, and I was quite satisfied with the results, but the tank fits quite tightly around them, and I experimented with more shims on the ears to see if I could gently "knead" more clearance from the tank. I have finalized the shim thickness at about 3/16", on each side. The fitment is not quite so slick, but the clearance makes me comfortable. The petcock may be an issue - my next step will be to contact my friend @ Acerbis Canada, and see if he will get me a petcock from them. (He is in Baja at the present time). The problem with all the aftermarket taps that I have seen, is that the spout is straight out, and presents an engineering challenge to get decent clearance, especially where the lower braces make contact with the biscuits, in the tap area of the tank. On my first Baja trip, I was "psyched" by the obvious size and weight of the tank, but I now have come to terms with the size - I am 6'4", and my knees fit in the rad vents of the tank quite comfortably. As far as weight, it is a bitch when full - I have marked off the gallons on the side of the tank, and I only fill the tank to the level that I arbitrarily decide is prudent. This is not a good practice in Baja, but non-the-less........................
__________
Yes, John, I tried the Husky (right spigot) tap - the bike needed the choke to run right. I am not 100% sure it was the tap, because I had to fabricate a 90-degree fitting to enable me to fit the fuel line. It may have been that which inhibited fuel flow. Any way, I am back to the stock petcock for now. I would be afraid to discard the "hard parts" rad guards even with the large tank. One of my friends (with the same tank, and no guards), let his bike tumble off his stool-stand, and the tank distorted enough to bend his rad. That was on a brand-new-unridden bike. I fell in 6th gear down near Coco's Corner on my last ride - I sprained my ankle (slightly), and scrubbed the tank pretty good, but there were zero other problems - that's enough proof for me! Also, I am afraid the rads would flop without some form of support to the outside. I may have misspoke re running on reserve - I don't open the right side tap until it is needed - I do run the stock petcock on reserve, as the regular "stem" is way too long when used in this tank. I hope to have some range with the right-side tap when the left-side runs out of fuel.. I have not had to use "reserve"of any type on this 525, it is such a fuel miser, so I really don't know what my "true"range is , nor what my "reserve" range would be.
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