Yokomo YR-4 2 Special

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EvolutionRevolution
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Yokomo YR-4 2 Special

Post by EvolutionRevolution »

This was built out of one YR-4 2 standard, 2 YR-4 2 Special wreckers, and some parts from a YR-4"M" junker.

Some build notes:
- Tracking down the special front belt for the YR-4 2 Special, which is shorter than that of the standard YR-4 2, was a pain in the ass. What is more annoying is that once installed I discovered the (NIP) belt slacks and skips even with the chassis adjusted for maximum belt tension :? , so I'll have to add a separate belt tensioner.
- Another problem was the choice of layshaft: The original standard layshaft from the YR-4 2 standard with locked spur size was discarded due to a chewed up spur. Both of the alloy Yokomo versions with center oneway I had were made out of supersoft aluminium :roll: (dear Yokomo, is it that hard to use good quality materials?) and had mostly chewed up pulleys. I had one decent rear pulley, so I rumaged in my parts boxes to see what I had for the YR-4. Found one delrin center oneway made by Alex Racing. So by combining parts I managed to build one good layshaft. Still, this chassis will get a slow brushed motor to keep the alloy pulley wear in check.
- Motor mount: one of the wreckers included the very nice alloy Yokomo hop-up.
- Hinge pins: Blackened steel ones were included with the YR-4 2 standard, while the Special junkers had regular steel ones - which had rusted (another WTF choice by Yokomo :roll: ). Guess which ones I used?
- Stainless steel hard universals on all four corners.
- Ball diffs are not super-smooth, but good enough. That little spring washer makes setting the diffs very hard. Not my favorite diff design.
- Battery hold-down and gearbox tops are wrong for the YR-4 2 Special: FRP instead of graphite.
- The bumper is an optional part that was included with the YR-4 2 standard.
- Tech Racing front camber link set. Other turnbuckles pulled off donor cars.
- Those little red shocks...I wonder if they actually do much absorbing?
- Avid bearings all round.
- Alloy steering shafts + ball bearings
- I have the correct wheels for the car, but not the correct tires. I would like to find street tires.
- And I've got the so-often-lost battery foam :lol:
chassis1.jpg
chassis2.jpg
chassis3.jpg
front.jpg
rear.jpg
motormount.jpg
Electronics have been sourced and will be simple: Sanwa 27MHz AM RX, Sanwa BL-Fighter ESC, Sanwa standard servo, 15 turns machine-wound modified motor

Charlie don't surf
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Re: Yokomo YR-4 2 Special

Post by Charlie don't surf »

I dig that Alex racing one way! Yokomo did make all of the versions of the one way in 3mm and 2mm in a hardened version that did not wear out like the grey ones- :wink:

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Re: Yokomo YR-4 2 Special

Post by EvolutionRevolution »

Charlie don't surf wrote:I dig that Alex racing one way! Yokomo did make all of the versions of the one way in 3mm and 2mm in a hardened version that did not wear out like the grey ones- :wink:
I honestly wonder whether the soft alloy is a marketing ploy to force people to buy the hardened version... :|

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Re: Yokomo YR-4 2 Special

Post by V12 »

Nice car. I had some of the old Yokomo touring cars as the YR-4, YR-4M and the YR-4M2. The YR-4M2 was all graphite with 3+3 saddlepack chassis where you could move the batteries for adjusting weight balance but beside this looks a lot like your Yokomo. I still have the old boxes but not any of the cars.

Most wearing part at that car was the rear diff outdrives. That white pulley/oneway at the layshaft is Alex Racing?
Maybe I have such tires here at one of my boxes or maybe a friend of mine.

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Re: Yokomo YR-4 2 Special

Post by Lonestar »

Cool - I dig the old Yr4's... I have one M almost restored and one NiB SP, plus a few miscellaneous M2's laying around (2nib M2's, one J-Pro) and check out my nitro Yr4-GP for sale (see link in sig...)... my first DTM was a M2 USA, it was fantastic for its time, I built in box stock for my first DTM race ever as I hit Austin in 98 and won with it in that new club I showed up at for the first time... one of my best memories of RC racing :mrgreen:

Those little red thingies that have a couple of drops of oil in them do little damping indeed, unless you have some crazy stiff oil in and are able to fill them right and keep refilling them all the time. On my YRF2SP, if I drop the front end by more than 2cm, the chassis hits the ground, bad :lol: what on earth was Masaaki thiking? Still, Masami won a crapload of races with them, so they must be working... somehow :?:

Wack the split washer off those diffs and get some belleville ones instead... makes your life MUCH easier, otherwise it's just so hard to get any diff right, as the tuning window is about 1/256th of a turn. This is poor design indeed. Maybe some other brand's diff spring might actually fit...

I have some nip period 26mm yokomo tires and inserts if you're interested, some new, some olds (must still have some stupid expensive but crazy sticky bitd 138g's barely run...) . Drop me a pm if interested and I'll look them up in my pile-o-tires I've hoarded all these years!

Paul
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Re: Yokomo YR-4 2 Special

Post by GJW »

awesome special mate, love the chassis!! been gathering parts for a build for a while now

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