The 2012 4×4 Ram weighed in at 5700lbs so using the following formula;
5700(.372+.05) = 2405
That is assuming the trailer ramps are about 40 degrees and using the high end of load on wheels value.

Required Line Pull = W(Gr+Cf)
W= Weight
Gr = Grade Resistance
Cf = Coefficient of Friction

They even provided some tables with friction and grade values already populated.

Coefficient of Friction
.40-.60    Steel on Steel
.40-.60    Wood on Concrete
.30-.70    Steel on Concrete
.02-.05    Load on Wheels
.05-.10    Load on Rollers

Grade Resistance
% Grade    GR
5             0.05
10            0.1
20            0.196
30            0.288
40            0.372
50            0.448
60            0.513
70            0.573
80            0.624
90            0.669
100           0.701
200           0.896
400           0.97
Vertical      1

After some play riding in Glamis and testing in the Arizona desert, the Moose thumb throttle is working well and is fairly easy to push.  The longer lever takes some getting used to since it places the idle position a lot further back.

The thumb lever was binding against the brake lever dust boot on the 400.  It needs to be a little further out on the handle bars so they don’t touch.  I had to trim the gripto get the thumb throttle body where it needed to be.

The throttle stop screw on the side of the thumb throttle walked in on both units and made it impossible to give the bike any gas.  Loctite fixed that.

I also had to go back to oem style throttle cables.  The ones that come with the Motion Pro twist kit are too long.

This time I will be not be removing the handle bars or plastics.  I am also installing a Pro Armor kill switch at the same time.  Both projects require the fuel tank to be removed.  I will document the kill switch details in another post.

1 Remove the old grips

Whoever installed the grips on these bars used just a touch of glue, so they were easy to remove and very easy to clean up.  I used a pair of wire cutters to clip the ends of the grips open, then tore them back like a candy wrapper.
The Pro Taper handle bars have a diamond pattern cut in the ends to hold the grips better, so they don’t need as much glue.

2 Remove the fuel tank

There are 2 bolts and 2 straps that hold on the fuel tank.  There are also 2 bolts holding the front plastic to the fuel tank.

• Remove the seat
• Reach over the air filter, towards the carburetor and release the straps from the frame.

• Remove the 2 bolts on each side holding the plastic to the tank.
• Pull the plastic away from the tank far enough to fit a wrench in between and remove the bolts that hold the gas tank to the frame.
• Turn the fuel valve to the Off position.
• Remove the fuel line from the carburetor.
• Lift the gas tank up off the bike.

3 Remove the thumb throttle

• Remove the 2 screws from the bottom of the thumb throttle assembly on the handle bars.  Let the cable and assembly hang over the hood.
• Remove the plastic cover from the side of the carb.  There is one Phillips screw near the top of the cover, then lift and pull it out.
• Detach the end of the cable from the lever.  You can pull down on the cable to create slack, then slide the ball out of the lever.
• Loosen the lock nut at the top of the carb where it threads in and unscrew the cable end from the carburetor.
• Guide the throttle cable out through the front of the quad.

4 Install the Motion Pro Twist Throttle Kit

• Guide the throttle cable back through the quad, reversing the way the original one came out.
• Thread the cable in to the top of the carb and attach the end to the throttle lever.
• Back the threads out until there are a couple rows showing inside the carburetor and tighten the lock nut.
• Assemble the twist grip and the cable half of the twist throttle and slide them on to the handle bar.
• Insert the cable in to the housing and attach it to the twist grip. then screw the two halves of the housing together to tighten it to the bars.
• Twist the throttle all the way open and make sure it returns to closed without any binding.

I read about swapping 450R shocks on a 400EX in several articles on the Internet.  They all said you have to grind the shocks, but none really described how to do it.  After holding the shocks in place, I could see that it would be much better to grind a little off the upper shock mount than the actual shock body itself.

After grinding the mount, the top of the shock body still hit where the nut is welded in for the body mount. (Inside the shock  mount tab)  If you really don’t want to grind on your shocks, you could cut off the bolt and tack weld the body mount right to the top of the shock tab, but I chose to grind the shock.  It was just a tiny shave off the surface to make it fit.  If you put the top of the shock in the mounting tab and wiggle it around, trying to line up the bolt hole, you will scratch the surface of the shock enough to figure out where to grind.

With the stock front compression settings at he first notch, the front of the frame measured 12 1/2 inches from the ground.  After swapping in the 450R shocks, the same spot measures 13 inches.  The a-arms are at the bottom of their travel with no rider.  the compression on the 450R schocks is all the way at the top (no extra compression)

Here is a picture of the stock 400EX front shocks before the work.  The frame height here is 12 1/2 inches

Here’s a shot of the 400ex stock front shock on the right side.

The 400ex shock is at the top of this picture.  You can see the 450r shock is a little bit longer.  When you take off the stock shocks, the a-arms drop a little.  When you put the 450r’s in, they use up all the space.

This is the upper shock mount before any grinding.  The shock hits the rear part of the mount at the lower curve.

Here is the upper mount after grinding away enough material so the shock fit without hitting the inner part.  The bolt hole still wouldn’t line up.  The top of the shock needs to be ground just a tiny bit.

In this picture you can see the small spot that needed to be ground off.  You could also try grinding the nut inside of the shock mount, but since it was such a small amount, I chose to do it this way.

You can see the 450R shock mounted in the 400x tabs in this picture.

This is the final product.  With the 450R  shocks mounted, the front end sits half an inch higher than stock.  The suspension feels much firmer on compression and the rebound is smooth.  Gone is the bounce of the stock 400 shocks.  After riding around the yard, the front end feels way more stable, and it doesn’t lean as much turning.  The real test will be in the sandy whoops at the river bed later this week.

Depending on the condition they are in, I’ll either try them out for one race or rebuild them right away.

I am documenting the installation procedure in case I need to do it again in the future, or if anyone else is trying this for the first time and needs some help.  These are the steps I took to convert the stock thumb throttle to a Motion Pro twist throttle.

Part: Motion Pro – Twist throttle kit
Machine: 2005 Honda Fourtrax TRX 400 EX

Tools used:

Wire cutters, Needle nose pliers
Phillips screw driver
14mm Wrench
5mm Allen key
8mm Socket
10mm Socket
400 Grit Sandpaper

Step 1 – Removing the Stock Thumb Throttle Assembly

• Remove all zip ties from the handle bars.
• You don’t have to remove the cable ties if you just want to lay the handlebars over the front fenders but it makes it easier to work with if you remove them all.
• Using the screw driver, remove the two screws from the bottom of the thumb throttle.
• Remove the throttle assembly from the bars and put the cap and screws back together loosely.

Step 2 – Removing the Brake Lever

• Using an 8mm wrench or socket, remove the two bolts for the brake lever assembly.
• Thread the bolts back in through the cap to keep it all together.

Step 3 – Removing the Switch Assembly

• Remove the 2 screws from the back side of the switch assembly.
• Be careful not to bend the assembly.  Slide it apart gently in the same direction the screws came out.
• There is a plastic tab at the bottom that will break if you try to twist it apart.

 Step 4 – Removing the Clutch Lever

• Remove the 2 bolts for the clutch lever assembly, using an 8mm wrench or socket.

Step 5 – Removing the handle bar

• Remove the 4 bolts on your handle bar clamps.  I have an aftermarket clamp because I switched to the Burgard 450 steering stem a while back.

Step 6 – Removing the Grips

• Even though mine were loose and coming off when I rode, I still had to cut them 3/4 of the way to get them to slide off.  I had my last set put on at a shop that used spray paint.  I wouldn’t recommend that method.
• Clean off the handlebars where the grips were.  The twist throttle needs a clean surface to mount over and the left grip will be too difficult to slide over a dirty or sticky bar.
• I used a 400 grit sandpaper.  If you have painted or polished bars, make sure not to go too far in or you will scratch/dull the paint where you will see it later.

Step 7 – Removing the plastics

• Remove the seat.
• They are the same on both sides, so just repeat these next steps for the other side.
• Remove the allen bolt with an 5mm Allen tool.
• Using a 10mm wrench or socket, remove the 2 bolts from under the front fender.
• At some point you may have to remove the tank cover.  Mine is already gone because the Burgard stem hits it at full turn and binds the steering.  Sorry, but I took it off so long ago, I don’t remember the method.
• Remove the hood from between the front fenders.  You pull up on the highest part, near handle bars.  Once the upper fasteners are clear, slide it towards the bars.  The lower part of the hood uses and L shaped anchor.
• The plastics should now be loose.  I just pulled mine forward until I had enough room to get to the straps on each side of the gas tank.

Step 8 – Removing the fuel tank

• Remove the 2 bolts from the top of the tank, just behind the steering stem with a 10mm wrench or socket.
• Remove the straps on each side of the tank by lifting them up over the lip on the tank.
• Make sure the valve is OFF, then remove the fuel line from the side of the fuel valve.  I used a pair of angled needle nose pliers.  Be careful not to bend the clamp, it doesn’t take much force to slide it off.  I couldn’t get a clear picture of the clamp, it’s kind of hard to get to.
• If you cant reach in to the clamp, try lifting the tank up on to the handle bar stem as much as the line will allow.  This slides the tank forward and creates more room around the line.

Step 8 – Removing the stock throttle cable

• First you will have to get the air intake tube out of the way.
• Remove the plastic grommet at the front of the tube then lift and wiggle the tube forward until you have enough clearance.
• If the tube is too tight to slide forward, loosen the hose clamp attaching it to the air box.
  
• There are 2 screws at the top of the cover.  Remove those and swing the top away from the carb, then lift it off.
• Grab the throttle wire(A) with your fingers and pull it down to create slack and slide the end of the wire out of the lever(B).
• If you can’t get enough slack with the cable, try twisting the throttle lever upwards (clockwise).
• Once the cable is disconnected, use a 14mm wrench to loosen the lock nut(C) from the cable mount at the top of the carb.
• Now unscrew the metal end of the throttle cable at the top of the carb.  There should be enough slack in the rest of the cable to allow it to turn as needed.
• Once the threads are clear from the carb, feed the cable back up towards the handle bars and remove the entire assembly from the quad.

Step 9 – Installing the Motion Pro Twist Throttle Kit

• Feed the carb end of the new throttle cable through the old route that the stock cable took.
• Align the threads to the carb and gently screw the cable guide in to the top of the carb.  Once the threads start showing a few rows inside of the carb, you can adjust the angle at the top and tighten the lock screw.
• Attach the end of the throttle cable through the guide, to the roller the same way the original cable was attached.
• Leave the side of the carb open for now.  You may have to remove the cable again, or adjust it.
• On the handle bar end, thread the throttle cable in to the twist assembly.  The cable will go in and make a 90 degree turn through the cable guide.  It might take a few tries to get the path correct.  You have to slide the plastic grip area over the end of the handle bar and line it up with the metal guide then get the end of the cable to secure in the plastic slot.
• tighten the throttle assembly to the handle bars.
• Twist the throttle and make sure it gives the carb the full motion that is needed and that it returns to idle with no binding.
• If the throttle movement isn’t smooth, check that the handle bar part is assembled correctly, then follow the cable back to the carburetor and make sure there are no kinks or tight bends.  Finally, check the cable inside the carb and make sure nothing is binding in there.
• Now you can install the plastic cover on the carburetor and put the air intake tube back in place.

 Step 10 – Installing new grips

• Check to see if your grips are lableled for right and left.
• I used Spider Grips M1 MX Grips from Rocky Mountain ATV and they were labeled for each side and also had an alignement arrow for the top.
• follow the labels or it wont fit your hands correctly.
• There are different methods for installing grips and I have had varying success with each.  This time I tried the more professional way.
• I used a heat gun at low setting to warm the grips.  They expand when warm, so they should be easier to slide on to the handlebars.  Don’t get them so hot that they get gummy or start to melt.  You still need to apply some pressure to get them on and you don’t want them bunching up.
• Apply grip glue following the directions for your grips.  I used a little bit more than the directions called for and it ended up dripping out of the grip and on to the plastic fender.
• I used Pro Taper Grip Glue.  You have to move quick with this stuff, it dries like super glue.
• Slide the grip over the handle bar and work it all the way on.  Mine went on easy until about half way, then they became difficult to push any further.  I had to twist and push at the same time, but keep in mind the top alignment.
• Check for excess glue and wipe it off if necessary.  Don’t use your fingers unless you like them covered with a hard shell of glue that doesn’t wash off.
• Twist the throttle and make sure it still moves.

This will be my 3rd order through them and they have always been perfect.

This time I got

• Helmet Mohawk
• Smith goggles (I forgot tear-offs at the last race and ended up scratching up my lenses trying to wipe off the mud)
• Motion Pro twist throttle kit
• Spider Grips
• A bunch of Neutron oil filters that were on clearance.