Kyosho Lazer ZX project

[HKS_TRD]

I think the variation on delivery times are dependent on the item being in stock or being made and also any anodising required

[terry.sc]

Any thoughts on why the center diff doesn't work so well? Just from looking at the instruction manual, there are four wave washers which act as the diff "spring," and my guess is that these do not offer the same range of adjustability as a standard spring or even the disk springs that Tamiya use in their center diff in the Avante. Or is it something else?

The centre diff works very well as a centre diff, the problem is that it's a centre diff. There is more than enough adjustment with the standard spring washers if you want to run it fairly free or pretty tight, but you have to adjust the nut in small increments if you want to tune it. It's not replaced because there is a problem with the diff, it's replaced because people would rather have a slipper in there instead which is more useful with more powerful motors.

[EvolutionRevolution]

I think the variation on delivery times are dependent on the item being in stock or being made and also any anodising required

Does Pargu still do custom anodising colors? I checked his site yestarday and he only lists blue and silver hinge pin blocks.

[HKS_TRD]

I think the variation on delivery times are dependent on the item being in stock or being made and also any anodising required

Does Pargu still do custom anodising colors? I checked his site yestarday and he only lists blue and silver hinge pin blocks.

He doesn't list it on the site but I sent him an enquiry and he then said he could do it. The custom anodising costs $10 extra IIRC I'm waiting on some bits as we speak which are going to be custom anodised

[Coelacanth]

I think the variation on delivery times are dependent on the item being in stock or being made and also any anodising required

Does Pargu still do custom anodising colors? I checked his site yestarday and he only lists blue and silver hinge pin blocks.

Yes, he'll do it for a really good price, but you'll have to ask, as HKS said. I bought a set of his wheels a couple months ago, he offered to anodize them blue for only $8.00 more, but I preferred them unanodized and polishable.

[stickboy007]

So I got most of my goodie parts in to get going on this project. Start tearing the car up a few days ago, only to realize that I need 3mm diff balls rather than 3/32" (d'oh!). So those are in the mail...

Then I realized that the belts I got are too thick and bind against the gearbox. D'oh! So I ordered some from Tough Racing...should be here in 2 weeks or so...

The Pargu parts did eventually ship and will be here any day now.

Now I have a workspace full of Lazer ZX guts waiting patiently for a rebuild

[Welshy40]

well if your going to use as a runner I would suggest getting a spare rear gearbox as I have designed a belt tensioner for this. One little tweak is needed and when time is available I will be able to make and sell the parts for you to fit. Hope its of interest.

[stickboy007]

So I'm about 90% there now as far as the rolling chassis is concerned. I will put some titanium turnbuckles on there, and then it's just a matter of the shocks. The stock ZX shocks are actually quite smooth (currently mounted with Losi big bore springs), but the front shocks are too short for the Fibre-Lyte tower on anything but the lowest mounting hole. I wouldn't mind finding a set of gold "medium" length shocks for the front, which I think is what the ZX-R used in contrast to the "short" front shocks on the ZX, but there are presently none available on eBay, with the exception of one nice pair at an extortionate $100 (really?!? It's one pair of shocks, dude!). One of my racing buddies might have a set of velvet shocks he can sell me, which I think would also be suitable for this chassis if the lengths are within range.

Installed parts so far:
Fibre-Lyte chassis, towers, transmission brace, servo mount plate, and steering brace
ARP alloy c-hub
Pargu alloy suspension arm mounts
MIP shiny CVDs
Ball diffs front and rear
New belts front and rear
Slipper clutch set

A few notes on the project:

The front c-hub carriers are ARP alloy units and are very nice; however, the vertical spacing inside the hub is larger than the steering block. I found that you have to mount the steering block towards the top of the hub, with a spacer underneath to close the gap to the bottom of the hub, in order to prevent the steering block from binding. The holes for the kingpins are also larger than on the stock c-hub, to accomodate 4x8 bearings, which is a nice touch.

For the replacement belts, I had originally sourced them from PolyBelt. They are very nice belts and I would consider using their belts for some other chassis, but on the ZX there is very little clearance between the diff pulleys and the gearbox. These belts have a spine that is just thick enough to cause binding against the bearbox, and so I had to order a set from Tough Racing which fit perfectly.

The MIP shiny CVDs were a last minute find. Basically, I found (and purchased) another Lazer ZX which had them installed and swapped them into this chassis. That other Lazer will be a runner. This one is a shelfie...for now at least

Since I had to rip apart almost everything to get to replacing the belts, I had some time to play around with the stock ZX layshaft. Now I understand better what's going on in there. Basically, the center diff is "locked" to the pulley that drives the front diff, meaning the front diff always gets full power, while the center diff really just adjusts the power distribution to the rear under acceleration. That means the best you'll get is 50/50, but on any surface or situation where the front grips first, the chassis will push on corner exit. Not bad for low traction surfaces...but bad for high grip surfaces (someone else on this forum pointed that out to me...now I can visualize it after playing with the layshaft for a bit). The Yokomo YZ10 (870C and '91 Works) was the exact opposite of this, whereby it has a friction plate that can rub up against the pulley that drives the front diff (or you can lock it for 50/50). That means you always get full power to the rear and are adjusting the front power distribution on corner exit - great for high grip tracks. So back in the day, if you liked it all loosey goosey, you got a YZ10, and if you liked the tighty whiteys, you got a Lazer ZX

One thing I do like about the Lazer ZX that the later model YZ10s didn't really have is that the center one-way pulley is adjustable. Basically, it just uses a friction plate that you can tighten or loosen against the housing for the one-way, giving you adjustable rotation on turn-in. I think this is possible to "rig" on the YZ10, but it is not straightforward and at least the Lazer was explicitly designed for it.

[rccars4sal]

Looks great! Im hoping to get to a lazer mega build project soon. Ive built ZXRs in the past, but never a complete zx, so it will be interesting to tear into that center diff.

[stickboy007]

Thanks! This is a very interesting chassis, although I am not too crazy about how much work it takes to get to the belts, or even just to do maintenance on the diffs...

[j0pp3]

Looks nice and clean! You seem to have learned a lot about this car by restoring it. You are right about the maintenance-issues on Kyosho-models from this era. The Optima Mid is also unnecessary hard to work on. The diffs are built in so deeply into the gear boxes like they were not intended to get any maintenance. Now You know why I used gear diffs in Mid at the VONats

[EvolutionRevolution]

A few notes on the project:

The front c-hub carriers are ARP alloy units and are very nice; however, the vertical spacing inside the hub is larger than the steering block. I found that you have to mount the steering block towards the top of the hub, with a spacer underneath to close the gap to the bottom of the hub, in order to prevent the steering block from binding. The holes for the kingpins are also larger than on the stock c-hub, to accomodate 4x8 bearings, which is a nice touch.

Maybe they are for flanged 4x8 mm bearings that are installed with the flange on the inside of the c-hubs?

[stickboy007]

Looks nice and clean! You seem to have learned a lot about this car by restoring it. You are right about the maintenance-issues on Kyosho-models from this era. The Optima Mid is also unnecessary hard to work on. The diffs are built in so deeply into the gear boxes like they were not intended to get any maintenance. Now You know why I used gear diffs in Mid at the VONats

Your Lazer seemed to handle pretty well with the gear diffs. Did you like how it felt at the VONATS?

Maybe they are for flanged 4x8 mm bearings that are installed with the flange on the inside of the c-hubs?

Good point! I'll try that...

[Welshy40]

Gear diffs work really well so long as you use thick grease and pack it in. Other issue is you also need the hardend out drives as the standard ones wear rapidly.

[stickboy007]

That sounds a bit like the Avante as far as the gear diffs go. I don't have any grease thick enough for it, and always liked ball diffs better for racing anyway. Bashers are a different story

I received some 4x8 flanged bearings in the mail recently and tried them on the ARP alloy c-hubs. Sure enough, that's exactly what it needed. So that problem is solved...

One thing I noticed about the MIP CVDs combined with the ball diffs (might also be an issue with the stock universals...don't remember) is that the right rear CVD hits the inside of the diff outdrive before the suspension is fully compressed. This puts a load on the gearbox, trying to push it to the left a bit. I can see this creating play in the bearing housings over time. I think this is due primarily to the little piece that the thrust bearing screw screws into not being fully flush with the inside of the diff outdrive. In other words, if you don't tighten the diff fully, then this piece gets pushed out and the dogbone will hit it as the suspension compresses. A bit strange, though, since the diffs are almost fully tightened (backed off ~1/8 turn). I am running non-stock rear hub carriers, though, and that may be creating an offset problem. I'll look into picking up a pair of stock rear hub carriers to see if that fixes this issue.