last-minute purchase: MX-4

[Mr. ED]

I had a couple free hours left in the hotel during my last weekend in Japan.
Still had the company car, toll-road card and creditcard for gas too... So I decided I could aswell take a trip to the next prefecture and check out the local RC-shop. I picked one of the same franchise I usually went to in Nagoya 'cause they all have a little corner of the shop dedicated to used cars and old stock.
I went for the parts, thinking I should be able to stuff them in still but came back with an MX-4 instead!
Big re-arrangement of the luggage but it got in Belgium safely, here it is:


And under the hood:


On the last day I went over to 2 more local shops knowing I had seen some spares in the first one:


and an M-chassis version sharing some parts:


Now my questions:
1. The slipper design on the buggy looks as if it requires a special spur, but someone mentioned in another threat that the YZ-10 will easily accept the MX-4 slipper. Does that work the other way round also?

2. The mini has no one-way drive on the lay-shaft, instead it uses a one-way instead of ball-diff upfront. Does this have any advantages? Should I put it over to the buggy, and if yes: should I keep the one-way on the layshaft also?

3. I have seen on the old Keil site that the MX-4 pictured there uses a flat sheet of carbon for the rear shocktower. Yet on mine it's a molded 3D part. Which would be the better one?

4. I would like to convert the car for 12mm hex wheels: using the wheel axle part of the MIP style CVD's in the mini. Unfortunately the male-female part of the CVD's are flipped between the buggy and mini. Which other CVD's have the ball-end on the bone, and the cup on the wheel axle? Anybody tried or seen this conversion yet? Or does anybody know where I could buy a sleeve of 6mm outside diameter and 5 inner: preferabaly precision-made in a HARD material?

[carloco8]

2. The mini has no one-way drive on the lay-shaft, instead it uses a one-way instead of ball-diff upfront. Does this have any advantages? Should I put it over to the buggy, and if yes: should I keep the one-way on the layshaft also?

Good question! With a front one-way and solid lay-shaft, you have instant free-wheel with the front tires when off power = feel of 2wd and tighter steering (off power). With center one-way (lay-shaft) and normal front diff, the front wheels will still free-wheel off power, but the diff action helps keep the front of the car stable. Off power turning will usually be improved over full-time 4wd, but a little less than a front one-way/solid lay-shaft. A good tuning technique for tight bumpy tracks Using a front one-way and center one-way together is the same as a front one-way only, but less rotating mass off-power, more noticable with on-road. On my MX-4, I run it with a center one-way and front diff.

[carloco8]

3. I have seen on the old Keil site that the MX-4 pictured there uses a flat sheet of carbon for the rear shocktower. Yet on mine it's a molded 3D part. Which would be the better one?

Stick with the molded rear shock tower. It absorbs all the force in a bad rear impact or upside-down crash. The graphite and fiberglass rear towers will crack, but the molded one will flex a bit more. I think its also an MR4-BC part/MX-4 upgrade?

[Mr. ED]

Thankyou for the advise. I'm not sure if the MR'-BC part is the same: I think I did see a nip spare of that one, and it looked very similar, but as the label did not mention MX-4 I decided to leave it.
The label on the diff pulleys mentioned both cars.

Any thoughts on the MX-4 spur? I have not taken it apart yet, nor found a manual yet, but it really looks like not-standard.

One more question: the car is now equipped with the moter of the previous owner: a 9turns tripple wind = about half of what I'd like to run. Which spur:pinion combo would you recommend for an 18 turn quad wind? I'm running 3300Ah Nih packs.
The slots for adjusting the moter position are so tiny Seen how difficult it is to replace the spur on this model that's a real negative point
.

[carloco8]

The spur gear is unfortunately crazy specific. Getting to it requires a good amount of disassembly too, but once you get the slipper right, its a set and forget thing.

As for the gearing, the internal ratio is 2.2 and the stock spur has 84 teeth. I'd start with 19-20t pinion to get you an fdr of 9.7 or 9.2.

Here's a pic of the gear, please ignore that it's stripped to DEATH!

[phoenix]

I have a manual/parts list if you are still looking for one ! Just send me an email. Already back home then ?

[phoenix]

I forgot: let's team up in the hunt for clear bodies then

[Mr. ED]

I forgot: let's team up in the hunt for clear bodies then

That's why I posted in your search.
But I really dislike this body shape and hope the protech body for the 870C I bought from Jay will fit

[minichamps11]

3. I have seen on the old Keil site that the MX-4 pictured there uses a flat sheet of carbon for the rear shocktower. Yet on mine it's a molded 3D part. Which would be the better one?

Stick with the molded rear shock tower. It absorbs all the force in a bad rear impact or upside-down crash. The graphite and fiberglass rear towers will crack, but the molded one will flex a bit more. I think its also an MR4-BC part/MX-4 upgrade?

The rear shock tower is the MR4-BC part. Many of the parts are interchangeable between the MX4 & BC. The diffs, rear belt, frt bulkhead moulding, wishbones & front hubs are indentical, & the rear gearbox main mouldings are interchangeable (but not identical).
The spur gears on my cars is an offset moulded part, I've never seen one like it on any other car. The MR4-BC took a standard Kimbrough style spur...but then it had no slipper and destroyed rear belts & diff screws as a consequence

[minichamps11]

The spur gears on my cars look like Carloco8's - an offset moulded part, I've never seen one like it on any other car. Also the slipper is a real pain to adjust but at least it has one - the MR4-BC takes a standard Kimbrough style spur, but has no slipper and so destroys rear belts & diff screws as a consequence

[Mr. ED]

o-oh I hope the spur I got on it will last long enough and will proove compatible with the desired ratio.
If anyone's got spare spurs, I'm ready to take quotes

[minichamps11]

Spurs should be easily available. In the UK, the sport version of the MR4-BC came with the MX-4 spur mounted on a plastic moulded layshaft pulley.
The race version of the MR4-BC (called a "Special" and only identified on the box by a sticker, in true Yokomo style) was the one that used a standard type spur, but mounted to an alloy layshaft pulley.

The standard BC was on sale here until 3 years ago - I'm sure CML distribution or DMS models in the UK would have spares still.