[completed] And now something completely different: YR4-M2 Type-J

[Lonestar]

HEllo folks,

I just just completed this one yesterday evening, this will be the last of my covid-projects as the track has reopened and the racing season has resumed.

I was gifted this car (and a few others!) about two decades ago by my racing mentor, my friend Jean-Giles (JG), who drove my young lad self to the racetracks in my late teens last millenium. He had a few electric cars but his heart was with IC so at some point he kindly offered me his cars... this type J was part of them. It has slept in a box for two decades, now was the time to bring it up to its former glory.

The Type-J is the second to last car on the YR4 touring platform, then Yokomo moved to the MR4 platform, with which Hara won the 2001 worlds with. The YR4 platform had its roots all the way to the YZ-10, and in the fast-moving environment of late 90's early 00's DTM, the limit was reached relatively soon. The car has the center flex spring, the final-generation shocks, and still is able to accept transversal stick packs (with the motor mount flipped to raise the belt to clear the battery), or saddle pack. The car that came after was the J-Pro which (from memory!) had a different motor mount and top-deck. For the record, the J-Pro was my first EP touring car ever when I arrived in the US of A - and JG handing this car over to me at some point after I was back to Europe was a big moment for me

(TBC)

[Lonestar]

Overall the restoration happened over the past few weeks. The point was to be able to track the car for raceday tomorrow, so this was done JIT I took a few pictures but not as many as I would have liked... let me share with you now

so this is the car as unboxed and after a very basic cleanup:



Tires are french spec tires, Medial Pro IAS, very decent all-round tires from bitd. the story behind Medial Pro is that it emerged from the ashes of Le Caoutchouc de Cournon, which was the hobby of a few engineers at Michelin (the full-size French tyre manufacturer behemoth). Cournon is right next to Clermont-Ferrand, where Michelin's main facility is located (including test track etc... ). Their products basically took the world by storm, in the late-80's to mid-90's, including a couple of euro and world champ titles, ahead of the american heavyweights of the time. Then the company disappeared as the folks kinda realized they preferred working on full-size tires business than the toy-car one... A few folks took over the assets and founded Medial Pro... which bellied up later on, then revived as 6-mik which is still active today as a "microbrand" of tires. Anyway, enough with the tire lesson

The car obviously has been run in the past, but is structurally sound:



The yz-10 genes are kind of obvious aren't they?



The bulkhead "caps" that protect the diffs aren't made of nylon like the offroaders though - they're CWF plates



The top deck "pivots" around the stand, overall the car is designed to offer a lot of flex around both axes... by 1998 standards! Still nothing compared to the modern marshmallow-cars however.

The transmission is filthy, and also uses ZD-502 diff pullies.





this car was run on a mostly 8th IC track, with lots of foam dust and some oil to glue this all together to the poor electric cars who dared venture there, and it shows

Full, short a-arm... definitely old-skool



(TBC)

[Lonestar]

Unfortunately no chassis protection here, the bumper sits on top of the chassis with no recess... so the poor CWF plate gets all the hits this will be adressed later.



notice the insane kickup angle for an on-roader, probably 15deg again, off-road genes

Steering posts are phat, as the top-deck also hooks up to them. They have been loctited to death, unfortunately I couldn't take them out of the chassis for a thorough check



Good old magnesium, simple design, motor mount. you can flip it top-down to have the layshaft up or down so the belt can clear the stick pack if needed. And it's filthy, too



I guess a slipper could be installed... just like on an offroader





That Lightweight CNC'ed pulley is a work of art...



On the other hand, that dinky flanged bearing which is supporting the layshaft pretty much all by itself on the driver's side is a bit scary



(TBC)

[Lonestar]

car is fully broken down and ready for thorough inspection



the foam bumper was neoprened to the supporting plate by my nitro-racing friend Jean-Giles



Time to work on the rear ball diff. As you probably know, there is no proper spring in the Yokie diffs from that era, just a split washer... so within like 1/100th of a turn of the wrench, the diff goes from locked to slipping. The bent diff screw "technology" ensure that the little differential action you *might* be able to get is totally neutralized by a diff that doesn't turn true What a crap design, unworthy of Yokomo, frankly...

One way to mitigate this is to use belleville washers, which my friend OverRC kindly helped me source more than a decade ago when I restored that YRF-2 SP (also inherited from Jean-Giles ). the last four I had went in there...



The rear diff is done. contrary to what one might believe it has been THOROUGHLY cleaned up. There is no way whatsoever to remove that black crud that is incrusted there, be it chemical, or mechanical. Ask me how I know



The bad news is I found out one of the ZD502's is shot with a couple of teeth missing... and ZD502' aren't cheap these days. And I remembered that when Jean-Giles gave the car to me he mentioned one of the pulleys was dead... I recalled this a bit too late I guess

The good news is, belts usually get very tensioned during braking, especially with the mild motor I will run in this old car... So the damaged pulley goes to the front trans, which has a one-way anyway, so cares about braking

Front one-way - notice the very finely flanged outdrives that hold the bearings



Both front one-way and rear diff done - love it!!!





Moving to shocks now - full disassembly needed. These are "bottom loaders" with c-clips and all, a la Gen-1 AE! Pistons are full of flashes, so it was time to remove these out properly.

Before:



after:



I'll let you guess which ones yields the better, more consistent damping

shocks done. Notice the bleed caps which were also used by the AE racers back in the day... Yokomo really was one step ahead in this matter! It only officially came to AE with the B4 iirc... crazy!



(TBC)

[JarLuck]

Awesome car! I remember running the YR4 series in the late 90's in NorCal. In the US we were mostly had the YR4-M2 USA which had the top deck shock up front and the sliding battery trays, and later the M2 Pro with the 8 battery slots and wider top deck. The J-car was something everyone wanted but was very hard to come by. Either you tried to order it from overseas or one hobby shop in SoCal (I think it was Ultimate Hobbies?) were grey market importing them and you could get one from them.

Can't wait to see how this one turns out! The YR4 and MR4 series are def. on my collection list, but haven't come across a decent donor car yet.

[Lonestar]

Awesome car! I remember running the YR4 series in the late 90's in NorCal. In the US we were mostly had the YR4-M2 USA which had the top deck shock up front and the sliding battery trays, and later the M2 Pro with the 8 battery slots and wider top deck. The J-car was something everyone wanted but was very hard to come by. Either you tried to order it from overseas or one hobby shop in SoCal (I think it was Ultimate Hobbies?) were grey market importing them and you could get one from them.

Can't wait to see how this one turns out! The YR4 and MR4 series are def. on my collection list, but haven't come across a decent donor car yet.

Thanks for your comments - yes, i recall the YR4 had a few significant NORRCA wins indeed, Masami himself raced it there iirc?

[Lonestar]

Anyway, here's the rest of the build, I hope I can finish this topic shortly, as you understood, it's a bit of a rush job

The UJ's are already assembled, and as most cars for this era, cannot be serviced, but they are in superb shape. the spindles' dinky steering throw stops are funny



front and rear hubs ready for being hooked up to the chassis. Very classical c-hub+kingpin design.



what i have noticed while restoring this car is how not fit-for-use tolerances were on this yokies from the late 90's... every suspension component pretty much bindss and has to be filed/cut/bored somehow... there was a lot of work making sure everything was smooth. Much more than I recalled, I was probably a bit less demanding of a racer 20 years ago

Now hooked up to the uber-short arms:



Now beginning to put things together



And with the one-way:



The antenna-holder had been glued to death to the top-deck, probably to prevent it from rotating all the time, no disassembly possible there... hopefully I can drill the body at the right place!



Old branded tools



More progress, with the iconic YR4 architecture coming alive:



(TBC)

[Lonestar]

time to start working on electronics. I wanted this car to be a runner, although a very very mild one (couple of packs per year at most...), still sexy with electronics from bitd, but practical. I've had my share of vintage runners the past couple of decades, I know I don't want to be bothered with a performance brushed setup that requires a cut every 3 packs, so I settled on a very mild mod that I could piece together from what I had available. Also, I wanted this car to remind me of my good times racing a (very similar) Type-USA, so I tried to get all period-correct electronics that I had owned back then:

Here's an Orion 17T arm from an early-2000's orbital, one of the only two non-correct pieces



notice the "cheap" balancing by removal of metal, as opposed to epoxy paste which protects the field better.

Off to the lathe it went, I like to true comms once in a while, it's a great feeling to turn a crappy comm to a brand-spanking new-looking piece of satin-finished metal... I don't miss doing this on raceday between runs, though



I can't believe I didn't take a pic of the can It's an Elite Speed Product. ESP was one of the many rebadgers who were tinkering with a variety of OEM mills bitd. Anyone remembers them? This is a D3 or D3.5 can, not sure anymore... I have bought quite a few mills from them when I was racing in Texas, I think they were in CA or something? Can anyone help? Then It went to the bench for a mild break-in, with a fan to cool it off more than to provide a load, really...





So in the end I resorted to just using a BHS, not optimal, but the only one that fits

The speedo matters, on all builds, especially runners! and the G10 is one of the 90's kings of the hill, with performance to boot, and that amazing LED bar a la Knight-Rider. Shame it was as reliable as a Yugo or Lada bitd, because it's one of the absolute coolest ever! And I also raced one (actually I had like two or three, when I got tired of sending them back to Tekin i just swtiched to Novak ) back then. Test fit here:



For the radio, I initially wanted to use one of my Caliber 3PS. Jean-Giles sold one to me back then, unfortunately I sold it to buy an M8 after that. Even though I have sinced purchased a couple of 3PS, I found out I was short of crystals somehow and then it just happened that I was able to grab this M8 from ebay, for a not-too-fair of a price, but my oh my, look at the full-full set!!! If like me you have a fetish for NiB RC electronics, you know this is something special. And the kicker is, I raced one bitd, too, so it'd be bang on-target!

I'm giving you the full strip-tease





Peek-a-boo



Daym I love it when it's like that with pretty much all the accessories including the frequency sticker plastic thingy



The M8 was the absolute shiznit back in the day...and that one is primo



Very interesting radio tray layout... not 2x4 or 4x2, but 3+2+3, and sliding.



even the direct tx-to-rx control cable is here! what a trip down memory lane... do you guys remember what it took to adjust your car without being able to switch the RF on? This pretty much nailed it!



The full monty, I'm telling you!



(TBC)

[Lonestar]

I told you the 2000's 17x2 orion arm was one of the first non-period-correct bits on this car. The other one is coming from the fact that I DO NOT want to run NiXX's any more - ever. Once you've tasted lipos, it's impossible to get back. Especially these days when you can cram 2x the amount of capacity we had 20 years ago in a such a tiny, neat lo-profile shorty package. The Type-J was designed to be competitive with saddle packs, but no way i'd be setting up the car for those. this is what I came up with:



Yes, masses are not too symmetric, but it isn't that bad actually. In any case, whatever the layout, that motor dangling on the rear left side means it's impossible to nail it perfectly anyway. And, again, for a 2x/year run, that'll be plenty good enough. The good news is, a shorty pretty much fits perfectly within the tape slots of the 4-cell side, that's an added bonus for practicality

The Airtronics RX with its cool neon-blue color, and the fancy "Z-connectors" which were just standard Futaba/JR/Hitec connectors (KO's have the reversal-preventing notch, but polarities are the same)... sanwa was the last one to switch to these then



with everything about fully set-up:



I'll spare you the attempts at getting the servo servo-taped to the chassis - yes, these were the good ole days or how to prevent the shorty from moving laterally, I actually recycled some steering posts from a Dex210 which I artfully x-actoed so they'd hold the pack about right... the armed tape would do the job longitudinally.

My friend Heretic had a great idea: switch the servo to the driver's side, and have the shorty on the right to help with balance. That would have worked if only those steering posts hadn't been loctited to death to the chassis... with the soft-alloy philips screws being stuck there till the end of times (and me too lazy to start over), disassembly was going to be a recipe for disaster. Heretic did rise up to the challenge though and agreed to take care of it in the next few months (no pressure, Maxime )

I also cut a chunk of plastic from a leftover Dex210 motor guard, to help the poor chassis not absorb all the energy when the car would grab a curb. Hot glue does the trick here , and It looks a lot less shitty in reality than on these artificially lighted photos. anyway, this will "naturally" be worn in shape

[Lonestar]

what about the body? Again, it had to be period correct...

I hesitated between a pretty rare by today's standards HPI 406 coupe, and a Stratus of some kind. In the end, I recalled I only ran the 406 for a couple of race meets bitd, and I wasn't quite impressed by it... the Strat' was the gold standard, I happen to still have a few (no Andy's though ) and I settled on a PF version



first rough cut:



wheel arches done (please pardon the shitty practice wheels which have seen better days )



aaaand it's fitted, now time to think about the paint-job!



All stars are lined up sometimes... my LHS (which is 150miles away, but at least in the same country!) had a few Custom Colours cans for sale as i was to order spares for the modern runners... so as I compiled the available decal sheets and the colors of the handful of cans they still had in store, I settled on an older YZ-10 decal sheet, and a few oh-so-90's hues and started masking and painting.



to be clear. I absolutely HATE painting bodies anything other than monochrome, typically white or yellow. To me, race bodies are consumables, I am always in a rush, I have zero artistic sense, so i am utter shite at doing bodies. This time I wanted to step up the game a bit, as this would be a body i'd be stuck with for a while, that had to look good on the shelf. So after a lot of cussing and swearing and a few x-acto cuts (yes I use masking tape...), and with some fluo pink paint splattered all over the workshop, I miraculously was able to come up with this:





I could shoot a few pics outside friday, just before raceday, when i decided I'd enter the BoTM contest. I fitted some period-correct NOS Yokomo 26mm rims and some japanese Agress tires also from back then and here is the finished product:

[Lonestar]

The kicker was yesterday, as I was racing at the GenevaModelCars track for the first round of the Geneva Series, our local championship with anywhere from 30 to 40 entries. The plan was to run the car mildly during the lunch break, with no performance in mind at all, but just to enjoy the warm and fuzzy feeling of being 20 years younger, and the hairy one of driving a one-way... with a 17x2, the car certainly is not fast by modern standards, as we run 13.5 boosted here, and 13.5 boosted is very fast already - I feel it can be compared it to 10-turn-ish with very solid batteries. So it was gently refreshing to see this car on the track at its own speed, and funky colors after experiencing a sea of monochrome Zooracing / xTreme blob cars hitting 50mph all day long.

Driving impressions? It's very smooth if only because the driver has to be due to the one-way at the front. We all drive front-spool equipped DTM cars, so it's a totally different driving experience, you have to anticipate a lot and be uber gentle if you every decide to brush the brake. I let my good friend Georges drive it a few laps and he commented how elegantly the car naturally enters the low-speed section of yesterday's layout. Overall, the general impression is that of a great smoothness, and mild-mannered handling - again, as long as you're not touching the brakes anywhere but with the front wheels pointing straight (and even then...).

I wanted to shoot a few videos but I was out of batteries unfortunately but I recall I was grinning whenever i was driving it or when Georges was driving it, because it felt SO DAMN COOL to see this piece of last millenium's touring car goodness on our track - and it reminded me of my own track experiences when living and racing on the Holy Land of RC more than 2 decades ago, with some extremely similar gear to what I owned back then! I'm so happy I was able to experience this feeling two decades after.

This is it... I hope you liked the car and the story.

Take care and stay safe everyone

Paul

[Dual]

Fantastic write up Paul. A pleasure to read the rebuild of this particular Yokomo (probably the most well known Yokomo touring car of the era as there where a few - M, M2, M-SP and J-Type) and appreciate all the little build tips you provided especially the one regarding the rear ball diff

How did the Tekin G10 run compared to the modern ESC that you would use? I remember this ESC being very capable in its time. Curious to hear your thoughts.

Will you be running this car regularly or more a blast down memory lane?

[works92]

Really nice build Paul ! And nice step up in the painting world

Once again, I learned a lot reading you (especially with the medial pro story)

PS: How do you feel the M8 compare to a modern tx ?

[Lonestar]

Fantastic write up Paul. A pleasure to read the rebuild of this particular Yokomo (probably the most well known Yokomo touring car of the era as there where a few - M, M2, M-SP and J-Type) and appreciate all the little build tips you provided especially the one regarding the rear ball diff

How did the Tekin G10 run compared to the modern ESC that you would use? I remember this ESC being very capable in its time. Curious to hear your thoughts.

Will you be running this car regularly or more a blast down memory lane?

Hey Vincenzo,

thanks for the kind words and glad you liked it. Yes I agree the YR4 platform is iconic in the history of EP DTM, it was one of the last chassis that was shelf-engineered from offroad bits with a few specific parts (namely: A-arms ). These were the days of the Street Weapon (which was an XX4 in drag), or the Schuey SST (a Cat 2000/3000). Tamiya had the TA03 but c'mon please gimme a break Then it got the other way around... the MR4-TC yielded the MR4-BX, the TC3 the BJ4, the XXX-S the XXX-4... then it took a few years for onroad and offroad electric to take their true, separate ways!

The G10 is a cool piece of kit. I reliably cannot compare it with anything I recall from competitive brushed motors, because I have totally forgotten racing brushed motors competitively. Let's just say I was very grateful it worked at all because it is a G10 and there aren't that many who survived un-melted The feeling was super-smooth, but then again it wasn't really getting stretched by that detuned 17x2 I used... It ran well, and above all, with no smoke

I might run that baby once in a while, say, once a year or so. I don't go to the track as much as I'd like to and I still try to keep myself somewhat competitive (at least locally), so I focus on the modern racers really... I dunno, maybe one pack per year? The thing is, it's dog-slow, really... and If I put any bigger powerplant in it, I'm worried it won't end well. So, yeah, 5mns per year at crawler-speed is good enough I guess.


Take care in Down Under!

Paul

[Lonestar]

Really nice build Paul ! And nice step up in the painting world

Once again, I learned a lot reading you (especially with the medial pro story)

PS: How do you feel the M8 compare to a modern tx ?

Thanks for the kind commens Phil!

The M8 is great - the menu is so intuitive. I currently run an M17 and it's night and day. I could adjust everything I wanted on the M8 instantly without opening the instructions. So well laid out and user-friendly. The M17 it takes a computer science PhD to manipulate it

Performance-wise, nothing to complain about. I was still racing my EX10 FM 5 years ago when in the middle between the M12 (which I didn't like and only kept 6mths) and the 4PX (which was great and I kept a few years). People complain about FM being slower than 2.4GHz, I never felt it when going back and forth.

Having said that - the ergonomics of the handle just plain suck. I think we've made a lot of progress on that end. And the radio is really top-heavy, too...

But this is all forgotten when you get to operate it on the track. There's nothing that feels like being 20yrs younger

A+ sur les circuits (on croise les doigts)

Paul