Mugen's MBX4XR 1/8 Scale 4x4 Racing Buggy

Nov. 01, 2005 By Glenn R. Viveiros

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Looking for an all out purebred 1/8 scale 4x4 racing stallion to flog at will at the local off-road track? The Mugen MBX4XR is all that and more! This fast and furious machine looks just as good on the track as it does off. It also performs just as good as it looks.

Mugen engineers really have some great ideas incorporated into this buggy and with the XR, you get quite a few goodies that some other manufactures sell as hop up parts. The kit comes in its own very nice carrying case that you can use after it's built. For those of you who have seen others XR's or the older XR ads in the magazines, the new kits do not include the nice Allen Drivers that the original kit had. When you open the box, there is a letter right on top informing you of this. Also in the new kits, the front differential no longer has the overdrive gears.

The nice thing about Mugen is that it's all or none, they don't seem to do anything partially. The Mugen MBX4XR is no exception. When you first open the box it is somewhat intimidating to encounter all the pieces and parts and then envision that you will be the one assembling them into a car. The advantage to building it yourself is knowing exactly how and where each part belongs. If you race, you will also inevitably have accidents. The outcome is typically broken parts and/or worn out parts which will have to be replaced. That is where the advantage of building it yourself comes in, making for easier replacement of broken and/or worn parts!

Once you start with the construction, the assembly is not difficult as long as you are prepared. This means having the right tools and a flat, roomy surface to work on, such as a work bench or in my case the kitchen counter (sorry, honey). The kit pieces come in individual bags which are alphabetically organized. This does not mean that each bag contains all the parts for each step, it just makes it much easier to find the right parts. The instructions come in two booklets for the XR kit. The RR Instruction Manual and the XR Instruction Manual. This appeared a little strange at first, but once you figure out that the XR Instruction Manual only replaces certain steps in the RR manual, it's smooth sailing and the car goes together like clockwork. You can really lose track of time while building the car (well, if you enjoy building them like I do you can). For those of you that may still be intimidated by this type of undertaking, it's no worse than assembling a model car. Simply take your time and read the instructions before building, then follow the instructions step by step and you can't go wrong!

Instructions and paperwork.

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Carrying case that the kit comes in.

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The instructions are very detailed, even if rather confusing in having to go back and forth between the two manuals. In each step they explain and also show the parts and fasteners required for that step. They also tell you which bags the parts will come out of for that step as well as the fastener type and size. The best advice I can give is to open each parts bag separately. If the parts are on a tree remove them from the tree and clean off the little plastic tits that may be left over and place them back in that bag with its label clearly visible. Then place them in alphabetical order. This makes it much easier to assemble and keep track of what you are doing. You start building the kit by assembling the differentials and the cvd's for the car. Step one is in the XR manual. Steps two, three, and four are in the RR manual. With this kit the silver ring and pinion gears are for the front differential and the black ring and pinion gears are for the rear. With the newer kits the overdrive gear set has been eliminated so it won't matter which ones go at which end. Next assemble the cvd's **Be sure to use Locktite on the set screws in the cvd's** After the differentials have been built you put them in their respective bulkheads and the center decomposable differential mount. Now that you have all three differentials built, you install them on the chassis along with the front and rear bumpers and the center cvd's. The servo saver and steering parts are next to be built and installed. This is step five and it's in the XR manual. Step six takes you back to the RR manual and deals with the installation of the front and rear shock towers.

Steering components and servo saver installed on chassis.

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Front shock tower installed.

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Rear shock tower installed.

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Steps seven and eight of the building process deal with the lower suspension arms, and lower suspension arm mounts for both front and rear. These steps are in the XR manual. Step nine takes you back to the RR manual and deals with building and installing the front and rear sway bars (as none of the tracks located close to me are smooth enough for these, I built them but did not install them.). Step ten is the assembly and installation of the pivot ball front knuckles, upper front suspension arms and front cvd's. Half of this step is explained in the XR manual and the other half in the RR manual. Step eleven is also half in the XR manual and half in the RR manual. It deals with the rear hub carriers, rear upper suspension arms and rear cvd's. In step eleven there are two different hub carriers that you can use. The instructions give the right length for the upper suspension arms that hold each one upright depending on the setup you choose.

Front lower arms and lower arm mounts. Click for full size image	Front lower arms attached to the chassis. Click for full size image
Rear lower arms and lower arm mounts. Click for full size image	Rear lower arms attached to the chassis. Click for full size image
Front upper arm, cvd and steering knuckle. Click for full size image	Front upper arms attached to the chassis. Click for full size image
Front knuckle, pivot balls and hardware. Click for full size image	Front knuckles ready for installation onto suspension arms. Click for full size image
Steering knuckles installed. Click for full size image	Two different rear hub carriers. Click for full size image
Rear hub carriers and cvd's ready for installation. Click for full size image	Rear hub carriers and cvd's installed on chassis. Click for full size image