RC Monster 8ight motor mount problem
 

Hello,

I recently purchased an RC Monster motor mount for my 8ight buggy. When I installed the Kyosho (46T) plastic spur gear on the center diff I noticed that the diff screws and the spur gear teeth rubbed on the motor mount. I attempted to shim the rear diff bearing back for more spur gear clearance away from the motor mount, but that ended up binding the driveline. I swapped between the stock steel spur and the plastic Kyosho gear about six times trying different shim configs and no shims before milling the motor mount on a lathe to allow clearance for the diff screws and spur gear teeth. I am a little disappointed with the motor mount, since additional work was needed. Most of the forum posts that I have read recommend using the plastic Kyosho spur gear.

Please advise if I missed something or if it was supposed to be shimmed another way.

Thanks

I have noticed the same thing with the Kyosho gears on my Mayhem with the factory aluminum diff mount, so the problem is not RC-Monster motor mount. Did you try the factory AE gear in there? No problem using metal gears if using the RC-Monster hardened pinions. Although I do prefer the plastic one in the buggy (silent), and steel ones in truck with more HP. For the kyosho spurs I use screws with smaller heads (thinner), different brands differ in head size, just so happens I had a bunch of kyosho screws with a bit thinner heads. I have also just touched the spur gear with a countersink bit to allow taller head screws to work.

The motormount is designed around the stock spur, since these spurs are more durable than the kyosho plastic spurs. With the new hardened pinions the steel spurs are a perfect match.

The Kyosho spurs require counter sunk screws, I assume you used these.

Obviously the kyosho spur requires more room than the stock spur; if the design was setup around the kyosho spur there would most likely be play on the center diff if the stock spur was used.

If the motormount is made the original mount is used as a template;

While some manufacturers/vehicles are using tighter tolerances and different type of spurs/diffcases I can imagine a conflict will appear when you use a different spur.

Sorry this caused you any problems; what would you like to see changed?

Bare in mind that the stock steel spur is way more durable than the kyosho spur. the stock spur would make it easier to get the gearing right.

I am sorry you had some trouble, Futurespeed. The motor mount was designed to be a direct replacement for the stock part, accounting for the reversed differential. It should fit perfectly with the stock spur gear.
The Kyosho spur is a different manufacturer's part and is slightly different in size - Losi also uses pretty small center diff bearing with a flange, so there isn't a lot of room to account for various manufacturers' spur gears and maintain perfect fit with the stock parts. It has been mentioned already, but we offer hardened steel pinions that can be run directly on the stock steel spur gear, so the Kyosho spur gear isn't necessary with our parts. :)

Thank you for the feedback. I may need to pick-up some hardened pinion gears. Is there additional noise when using a steel spur with a steel pinion?

FYI - I removed about 0.5 to 1mm of material from the diff side of the motor mount. The material that was removed started with a diameter 2mm larger than the bearing opening and went to a diameter slightly larger than the teeth on a 46-tooth Kyosho spur gear. This allows for the clearance of the counter sunk diff screws and the spur gear teeth. Due to the offset of the Kyosho gear those were the only two conflicting areas that needed additional clearance.

Thanks again for the feedback.

you are welcome;

yes, there will be a bit more noise coming from the steel to steel pinion/spur. But it's worth it. (unless you are looking for a super silent warrior)