MR-4BX series has been produced for only a couple of years. the first version came at ’06 and replaced with B-Max4 which was different from previous yoke buggies at ’08.
MR-4BX series is like the last blood of traditional Yokomo to me. and I see the same blood on Jconcepts BJ4.
a few prototypes on Japanese magazines were not far from MX-4 YMP until 2004. they put a slipper clutch, moved the motor mount forward, put B4 rear arms and losi style steering knuckles, and so on.. through early ’06
my friend who has been working with Yokomo and other japanese rc companies told me their CNC machine was never stopped for a couple of years to make new prototype parts. I know it never stopped before MR-4BX. but more than a few MR-4BX prototypes have spotted on Yatabe arena for years.
I have managed to get a nicely used Worlds edition last month. and took some pics with my factory edition. they both came at ’07.
the differences between them are main chassis, F/R shock towers, top deck(s), steering, rear bulkhead, and a few misc parts
MR-4BX Worlds came with a new camber mount which allows only the longest upper rod setup. also the steering is different than previous 2 versions
this new camber mount can be installed on older versions as well
the original and Factory edition’s front tower provide 6 points of upper rod mount position. the tower is compatible with the original through Worlds. and the inside position provides pretty much same result as Worlds’ front camber mount
the steerings are quite different. I hope I can feel the difference while I’m running this Worlds edition. but, didn’t have a chance so far.
this steering was introduced with MX-4. prototype MX-4 still had older servo saver. and the first time I saw this was in MX-4 kit.
but the difference is the angle. this steering system on MR-4BX is tilted for better handling.
this 2 piece structure was came from the prototype and applied to the production models through the 1st and Factory edition. but Worlds edition came with 1 piece chassis
MR-4BX Worlds came with this 1 piece chassis with 2 extra holes for new steering system. please ignore the stainless screws on the Factory chassis. I’d go back to the black steel screws.
the top deck, now it covers the rear belt. and new camber mount is here
Factory edition had 2 piece top deck like the original version. but the rear piece was improved that older one has clearance problem with the belt
the rear top deck from the ’06 original version
Rear Shock Mounting
there were a few guys tried this before Worlds edition came. the shocks were moved to the back end of the car.
also they put a camber mount like the front end
the original and Factory edition had same suspension geometry. the shocks can be moved to the back end with this stock mount plus a few tricks
the new aluminum part which holds the the shock tower is changed along with new bulkhead and camber mount