Kyosho Inferno MP-7.5 Sport/GS .21R





How can you not love an 1/8 scale off-road buggy?  These machines dominate the off-road circuit and are regarded  as an elite form of R/C racing.   Many people are scared away from this class racing buggies because of the high price tags and complex assembly that is normally associated with such a high performance machine!



The Kyosho MP-7.5 Sports RTR is the ticket.  Boy have times changed from the days when you could only get a ready-to-run car at your local Radio Shack.   Today there are many competition-grade buggies available in a RTR package.   However, none can boast that they were closely based on the World Champion MP-7.5.   The Sports RTR carries on many of Kyosho’s proven world dominating engineering, but with the ease of use that makes this a perfect for any novice (or seasoned pro).


Despite the fact that this is a RTR, this is no toy!. When properly setup it has everything you need to stand up to the big boys on the track!

The Sports RTR comes as you see if pictured above, complete with a Futaba-built Perfex 2 channel radio system already installed. The cars body comes cut to fit, prepainted, and completely decaled. The Sports RTR is outfitted with Kyosho’s new GX-21R nitro engine. This new big block features a two needle slider carb with an oversized blue heatsink.




Model name: Inferno MP-7.5 Sports
Type: 1/8 Scale 4WD Racing Buggy
Distributor: Great Planes Model Distributors
Length: 16.1″ (410mm)
Width: 12″ (305mm)
12.9″ (328mm)
Front Track:
12.4″ (315mm)
Rear Track:
12.6″ (320mm)
7.1 lbs. RTR
Chassis: 3mm Blue Anodized Aluminum
Kyosho GX-21R (.21 ci.) (installed)
3 Sealed, Metal Bevel-Geared (Front, Rear, Center)
Bearings: Shielded Ball Bearings
Damping: 4 Aluminum Oil-Filled Shocks
Tires:  Medium Compound Step Pin
Wheels: 10-Spoke White Nylon
Requires: 12 AA Batteries & Glow Fuel
Transmitter Used: Futaba-designed Perfex 2 channel system
Servos: (2) Perfex High Torque
Street price:
$400.00 – $450.00




Tough, lightweight Aluminum Chassis, Belly Pan, and Shock Towers

Well written instructions

Pre-painted and decaled body

Excellent handling.

Excellent Speed.

Many aftermarket performance upgrades available




Had Some trouble getting the engine to run right (See text)




After having a chance to see and drive a race-ready Kyosho MP-7.5, I had a basis of comparison on the Sports RTR.   It was obvious to me that it was a great concern for Kyosho to uphold the 7.5’s great reputation.   Make no mistake about it, the Sports RTR is a real MP-7.5! 

There were only some minor component differences between the Sports and the 7.5 kit, mainly aluminum parts, such as the chassis, shock towers, and belly pan.  The 7.5 kit comes with a better set of race-ready shocks as well.   Other than that, if you put the two cars side by side, you would be hard pressed to find any differences.



The suspension on the Sports RTR has been duplicated from the same championship dominating machine that Kyosho has kept in the winner’s stand for years.   Most of the components are made from molded nylon.  This material proves to be very strong, yet provides just the right amount of flexing to compete on the track with the big boys.    The aluminum steering spindles and hinge pin braces provide added reliability. 

Having put this car through it’s paces, I can attest that this suspension system will stand up to the job!


The Sports RTR is built up from a 3mm blue anodized aluminum chassis plate.   While the blue color looks awesome out of the box, I would soon find myself looking at the bare aluminum on the bottom after a few hard runs removed the coloring.  I did not feel that the chassis is as strong as the race-ready kit, but it certainly gets the job done.


On the top of the chassis you will find the major radio components, engine and drive train.  Comparing to the 7.5 kit, the layout is identical.    The Sports does feature a spacious sealed radio box with a separate compartment for the receiver and battery.  The receiver is real easy to get to in the event you need to make a quick crystal change. 

Everything is neatly laid out and very easy to work on.



The factory installed Futaba-designed Perfex radio system is a little lacking in features that you might like to see when competing on the racing circuit, but it does have all the necessities to get the job done such as dual rate for steering, throttle and steering trims, and servo reversing on each channel. 

The servos are high torque and fast.   The steering is very responsive and concise.   

The dual vented disc brakes are awesome.  They stop on a dime and give you the added control needed when passing on the inside.   The brake tension is adjustable by moving the collars and/or the radio linkage on the servo horn.  It would be nice to have end point adjustments (EPA) so adjust the amount of braking without making linkage adjustments.   Overall the factory settings were very effective. 



The Sports RTR features the same proven drive train found on the MP-7.5 kit.   Metal-gear differentials are used in the for the front and rear drive train, and a similar diff is found in the center to transfer power to the front and rear wheels.    The diffs are all sealed with an o-ring so they can be filled with a silicone fluid.  After taking them apart, I noticed that there was a light coat of grease applied by the factory.  After talking with some racing buddies, they suggested  5000 or 6000 fluid in the front and rear diffs and a heavier 7000-8000 wt. in the center diff.  However, I am not planning on racing this competitively so for the time being, I left them alone.   After 15 tanks, I opened them up and found that the grease has all but disappeared.   At this time I took the advice of my buddies and added the fluid to ensure that I would not be replacing the diffs in the near future! 

The only main difference I saw between the race-ready Mp-7.5 and the Sports RTR was that the sports uses 4 gears in each diff and the 7.5 kit uses 6.   Again, I did not see much difference in performance between the two machines.



The Sports RTR comes complete with a new Kyosho GX-21R racing engine already installed.  Keeping with the ease of a RTR kit, a pull-starter is included eliminating the need for a starter box.   The new engine features a large blue aluminum cylinder head for improved cooling.  A slide carb is already connected to the servo.  All that you need to install is the air filter.
The exhaust system is unique in that is is a two piece muffler and a silicone coupler to attach it to the header.    This muffler provided excellent results from the mid to high end range, but could have used a little more gusto in the low end!


The Sports RTR comes complete with a set of white nylon 10-spoke wheels and medium compound  step-pin tires that have been glued to the wheels at the factory.   Foam inserts are not provided.  They left this up to the individual driver to match his driving style.




Here it is! Out of the box and ready for action. Just add 12 AA batteries (4 for the receiver and 8 for the transmitter), fuel, and we are off to the track!





Before I began any serious running of the Sports RTR, it was necessary to break-in the engine.  the best way to do that is to set the high speed needle open 2 turns and run the car being careful not to run more than half throttle.   I ran a total of 4 tanks leaning the needle valve by 1/8 turn each run until the engine reached its full potential.   

On my first run on a rough dirt track, the engine kept flaming out on me when I hit full throttle.  I made some adjustments to the needle and the problem still persisted.   I made a quick call to a local hobby shop and they suggested switching the factory plug to an OS A3 plug.   They also suggested switching to Duratrax Red Alert 20% racing fuel.    Following these suggestions, all my engine problems went away and this buggy really came to life.


The track I was on was best suited for monster trucks, but that was not going to stop me.   I was going for broke.   As I punched the throttle, the Sports RTR jumped to life going instantly airborne after hitting each mound of dirt.  If there was any weak component on this car, I was sure to find it on this track.   After 3 tanks I stopped to thoroughly inspected every nut and bolt and other than the belly pan missing a lot of its pretty blue luster, I was please to find that it was perfect and ready for more!

I moved to a paved oval track next.  While this is not what this buggy was designed for, I was interested to see what its top end was like and how it would handle.   Can you say “Blistering fast?”  While the cars did not handle the turns too well, it performed amazing on the straight-aways.  I would guess 45+ MPH!


Once the racing on the dirt track was finished, I was able to get a couple of practice runs.  The Sports, in my opinion, has set a new standard for the RTR 1/8 scale buggy market.   Not that this is too hard to believe considering Kyosho has been the leading world champion.    The steering is very responsive, coupled with the factory setting on the suspension, I had no problems taming the track!   

I did add some foam inserts to the tires and that rose the Sports to a different level.   The handling in the turns was drastically improved.   Jumps were awesome as the car remained level while airborne.   Once the wheels were back on the ground there was no stopping it!

On my final run I did get a chance to run against a Duratrax Axis.   What a blast!  We were both at about the same driving skill.  The Sports had more control in the turns, but the Axis was a touch quicker on the straight-aways.  The Sports was better on the jumps gaining more distance and taking off with vengeance once back on the ground.    Who won?  Neither of us.   The Axis hit a turn hard and broke a lower A-arm and I bent a shock on the last jump forcing the car to veer to the right.   A DNF for both of us.   Buy Hey, there is always next weekend!



Kyosho’s MP-7.5 Sports RTR 4WD Racing buggy is one awesome machine.   With the 7.5’s long and impressive track record, it is no wonder this car is anything but!.   

The powerful Kyosho GX-21R engine gets the job done with a ton of power left over.   The Sports is truly a RTR – Just add batteries and fuel and your are off.   It comes pre-assembled, pre-painted, and pre-decaled.  Whether you are a beginner interested in getting into 1/8 scale racing or a seasoned pro, I am sure that the Sports will prove to be a very exciting and capable machine.




Distributed by Great Planes

Futaba R/C
Batteries Supplied by
Cermark Inc.


Distributed Exclusively in the U.S.A., Canada and Mexico by:
Great Planes Model Distributors
P.O. Box 9021; Champaign, IL 61826-9021

Futaba Corporation of America
Distributed Exclusively in the U.S.A., Canada and Mexico by:
Great Planes Model Distributors
P.O. Box 9021; Champaign, IL 61826-9021

9830 Bell Ranch Drive
Santa Fe Springs, CA 90670
TEL: (562) 906-0808 (Information only)
1-800-704-6229 (Order only)
FAX: (888) 680-5880
EMAIL: [email protected]






About Author

Leave A Reply