Yeti Jr - New (old) Little Project

[AK KRAWLER]

So, I purchased a little, used Yeti Jr from a member here and this thing looks like it’ll be a blast. It is in really good shape and already has a 4100kv Brushless Mamba Motor and Mamba Micro X installed.

A couple small issues and most of it was me not researching enough before I “had” to have it. In typical fashion, I bought it and immediately put it up on a shelf for a couple months, while I worked on other projects.

I pulled her down the other day, only to find out it mad a nasty grinding noise when it was pushed around and while trying to drive it. No worries, it’s a tiny little rig and there is not much to go wrong…
I first thought the front did was stripped. I tore into it, only to see that everything looked good. Put it back together and the noise was still there. Okay, it still has the open diff front end and I think it was just wore out. I believe the spider gears were slipping due to excessive slop in the diff itself. I cleaned it all up and did the JB Weld DIY locker. That took care of that issue and the diff is now quiet.

Now, onto the current issue.

The little Mamba motor has a tiny 2mm shaft and the tiny 10 tooth pinion was loose on the motor shaft. This little guy has the small grub screw I have ever seen… it makes the tip on my 0.050” hex driver look big. With some research, it looks like this may need a 1mm hex driver.


Well, no one around here has this little of a hex driver, so I’m a bit dead in the water for now. I checked the only hobby shop we have, as well as all the hardware stores, big box stores and auto part stores.

Here she is.






In tear down.

[AK KRAWLER]

I found a small precision tool kit and it had a 0.9mm driver in it that worked.

The pinion is installed, gear mesh set and almost put back together.

One of the bullet connectors broke off of the motor, so a little soldering to do, a few more screws and she’ll be ready to rip around a little.

[AK KRAWLER]

Everything soldered up and put back together.

This little thing is so fast it’s pretty uncontrollable, but a blast at the same time.

All that work, for one run of fun. Didn’t even make it through the battery without grenading the right front axle shaft. And the steering on it needs som serious attention. It looks a super slow, laggy and never centers.

[twade984]

These are fun little rippers, my BIL has the can am version with a little brushless setup. It will damn near backflip from a stop on carpet


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[Fallen]

I had the same problem with steering on my Yeti Jrs.

I ended up deleting the servo saver, and that fixed it.

I had a bearing (not sure what size) that was big enough to take up the space of the servo saver, so I put that in its place.

Now my steering centers well, but it is still slow to steer.

[AK KRAWLER]

Originally Posted by twade984

These are fun little rippers, my BIL has the can am version with a little brushless setup. It will damn near backflip from a stop on carpet

This one does some crazy weird launch thing, hope on one wheel, spins around and lands on its back like a turtle

Originally Posted by Fallen

I had the same problem with steering on my Yeti Jrs.

I ended up deleting the servo saver, and that fixed it.

I had a bearing (not sure what size) that was big enough to take up the space of the servo saver, so I put that in its place.

Now my steering centers well, but it is still slow to steer.

I’ll give that a shot when I replace the axle shafts, thanks man

[Fallen]

Oh, and another tip, possibly for the future:

The Holmes 380 V2 2200kv motor is perfect for this truck, and works with your current ESC. The motor comes stock with 4mm bullet connectors, so you'd have some soldering to do in order to make it work. The other quirk is that the motor shaft is so long, you have to put some washers between the motor and the motor plate, to push the motor aft in the chassis.

It gives you back the low speed control but has tons of torque and great top speed. Considering that your wheels and tires are bigger than mine, you'd probably like it even more than I do.

[AK KRAWLER]

Originally Posted by Fallen

Oh, and another tip, possibly for the future:

The Holmes 380 V2 2200kv motor is perfect for this truck, and works with your current ESC. The motor comes stock with 4mm bullet connectors, so you'd have some soldering to do in order to make it work. The other quirk is that the motor shaft is so long, you have to put some washers between the motor and the motor plate, to push the motor aft in the chassis.

It gives you back the low speed control but has tons of torque and great top speed. Considering that your wheels and tires are bigger than mine, you'd probably like it even more than I do.

Thanks man!!! I was wondering about the Holmes 380.

For me, I am more of a fan of controlled power and yes, I know it is my own hand controlling the transmitter, but the sounds of 2200kv, sounds way better than 4100kv.

[AK KRAWLER]

I completely forgot that I hadn’t ordered them yet, so I just ordered the replacement front axle shafts.

I am really interested to see if I can find a nice balance between, speed, controllability and low speed control.

Sounds like a fun challenge.

[Fallen]

A challenge indeed. My Yeti Jr with the Mini Cooper body looks more 1:10 or 1/12 than 1/18. So it gets driven at faster than 1/18 speeds. The short little wheelbase has problems with that, and the rear end likes to end up in front.

The 2200kv motor is still too much top end for the Yeti Jr's suspension and wheelbase. But it's fun to run it at the ragged edge and see how well you can control it.

[AK KRAWLER]

Originally Posted by Fallen

A challenge indeed. My Yeti Jr with the Mini Cooper body looks more 1:10 or 1/12 than 1/18. So it gets driven at faster than 1/18 speeds. The short little wheelbase has problems with that, and the rear end likes to end up in front.

That’s definitely the understatement of the year…

Originally Posted by Fallen

The 2200kv motor is still too much top end for the Yeti Jr's suspension and wheelbase. But it's fun to run it at the ragged edge and see how well you can control it.

I’m thinking of trying something less kv than 2200kv, but we’ll see.