Rebuilding my JRX Pro-SE

[HS-YZ250]

Since my other car projects are about 90% done, it makes sense that I forget about them and dive into another.

Here's my JRX Pro-SE. My parents bought it for me very late in my RC car racing phase so I raced it very little and did very poorly coming off an LXT. I actually raced it more with foam tires in a parking lot series after the dirt tracks closed down than I did on dirt, but it's spent most of its life since the early 90's sitting in a corner.

So here are the immediate things I'm looking at:

Last time I got it out it bothered me that the steering had gotten so sloppy. So, I'm putting in a NOS MIP Bearing bellcrank set I found a couple of years ago. When I pulled out the old parts I was reminded that I had lost one of the "shoulder bolts" that go in the steering. I'm hoping it's possible to get this bolt without buying a whole Sector Arm kit (A-1510), but it seems like it's a special part as shoulder bolts aren't made like this. Anyone got a lead before I go buy a Sector Arm kit off eBay?

I wanted to replace the rod ends and balljoints together if possible, since the car's done a bit of bashing over the years. I hope I can do this on my LXT as well. I found these Losi branded parts on Amainhobbies because they were #4-40 threaded. The metal ball joints themselves worked (though a couple were the wrong thread), but I found the rod ends were too big to work with either my original tie rods, or modern 3mm tie rods. Did Losi use a larger tie rods with these? I found some RPM rod ends if all else fails.

A while back I added front axles and rear hexes to run B3 front and rear wheels (seen in first pic), I think after reading on this forum. Maybe it was another. This setup was a little wonky, needing a stack of shims and to grind some clearance on the rod ends to work. I wanted to get a better setup on at least the front, so I found the parts for the B4.1 Front Hex conversion. Ran into problems with the travel of the steering arm on the LXT caster blocks, so roughed up a set that I 3D printed. To get the full range of steering, I had to raise the steering arms a good deal to get over the pivot for the hinge pin, which will require me to raise the ride height of the suspension arms to compensate, which I'm not excited about. Also, in the first attempt, the front end got really wide.

I thought I might have two options here. First, I could add front wheels for a B44, which are deeper offset, and/or a set of associated 4mm front hexes. The other was to see if I could try and get newer associated or losi caster blocks and steering arms to fit up front here.

Has anyone done a hex conversion on the Pro SE?

That's it for now. If I can get these questions sorted I'll relocated the steering servo (did a lousy job back when I put it together) and convert it to brushless power. Still has a Reedy 17T with a Trinity endbell in it from ages ago that needs a lot of attention. I also need to replace the rear bulkhead because one of the inner hinges has been loose since I caught the corner of a building with it back in the 90's. I'll probably only ever run it on pavement in the future, to save wear and damage, but also because I don't have any tracks near me that I know of.

BTW, this kit came with the XX transmission and I also added a Hydra Drive, and a Jammin Jay Steering Enhancement kit. Maybe I'll do a new body for it as well, if Blue Groove makes them.

[HS-YZ250]

I've made good progress in adapting steering components from a TLR 22 4.0 to my SE, which will let me run TLR 22 front wheels.

I'll add pictures of that later, but in my searching I noticed that losi threaded shock bodies are fairly available and would love to put a set on.

Does anyone know if the threaded shock bodies for the XX and XXX can be put directly on the Pro SE shocks? If so, do I need a set of 0.9in for the front and 1.2in for the rear?

https://www.ebay.com/itm/114945657972?epid=1300037374&hash=item1ac34b8c74:g:xO4AAOSwog5hH9-O

[RCveteran]

I think these days if you are trying to avoid the hodge podge of parts, shims and what ifs is to run the direct fit 2.2" wheels available from JC racing out of England. Order a couple sets to share the shipping and frankly they are a great value. No affiliation, just a guy who has used every combo back in day before these were available.

https://www.jcracingproducts.co.uk/wheels/losi-jrx2

[RCveteran]

Does anyone know if the threaded shock bodies for the XX and XXX can be put directly on the Pro SE shocks? If so, do I need a set of 0.9in for the front and 1.2in for the rear?

https://www.ebay.com/itm/114945657972?epid=1300037374&hash=item1ac34b8c74:g:xO4AAOSwog5hH9-O

All the info you need about running these is here. Use modern losa5015 cartridges and swap over your shafts and spring cups. Problem is even these are getting hard to find these days and subject to the high vintage markup as a result. You could probably adapt some takeoff 22 shocks easier.

https://www.rc10talk.com/viewtopic.php?f=27&t=19073

[HS-YZ250]

I think these days if you are trying to avoid the hodge podge of parts, shims and what ifs is to run the direct fit 2.2" wheels available from JC racing out of England. Order a couple sets to share the shipping and frankly they are a great value. No affiliation, just a guy who has used every combo back in day before these were available.

https://www.jcracingproducts.co.uk/wheels/losi-jrx2

Those would have been nice a little while back! I know I've bought from them for my YZ-10. But, I'm already pretty far down the hodge podge rabbit hole, though. Thankfully I have the means to design and 3D Print my own parts so the TLR 22 4.0 parts went on pretty quickly. Just waiting for some of the more expensive stuff I put off buying before I thought I could make it all work. Definitely a little more weight out at the wheels, but this'll probably never see more than a parking lot or tennis court ever again. Also, whatever I do here I'm gong to try and carry over to my LXT as well.

All the info you need about running these is here. Use modern losa5015 cartridges and swap over your shafts and spring cups. Problem is even these are getting hard to find these days and subject to the high vintage markup as a result. You could probably adapt some takeoff 22 shocks easier.

https://www.rc10talk.com/viewtopic.php?f=27&t=19073

Thanks for that confirmation! After I posted I found the part number for the 0.6 in long bodies and knew I was going to have gotten this idea too late. Should have revisited my Losi when I first started messing around with my Rocky. Got spoiled; so much more Kyosho stuff floating around the world!

Also, love the 5-link build! Every once in a while I daydream about building one myself.

[HS-YZ250]

So, while I'm waiting for a few parts, here is some progress.

First, I got lucky and found an NOS pack of shoulder bolts, enough to redo my LXT as well, when that comes.

That let me pop on the NOS MIP Steering bellcranks with the bearings

Then I modeled and printed a set of caster blocks to carry the TLR 22 Knuckles. It was interesting to see how much beefier modern parts are compared to the originals.

Currently they have Lazer ZX6 wheels mounted, but ordered some TLR 22 wheels. The current width seems pretty close to the rear spaced out with the B4 wheels, but I'm imagining I'll have to make another iteration to bring them in a little. There's not much room to do so, though. I'm also probably going to have to play around with location of the stud for the upper link to preserve the Pro SE's suspension geometry (actually, that of the Jammin Jay Steering Enhancement Kit), and I'm curious how wonky the steering geometry will be.

I decided to also try and convert the ball studs to newer losi 4.8 mm's so I can refresh all of them, since the 3 mm thread just fits through the 4-40 holes. Meanwhile, looking at parts diagrams I found the 4-40 studs are used on the center steering link of the TLR 22, which seemed odd since the stud diameters are the same as the smaller vintage ones, but I'll carry that over so I don't have to re-drill the sector arm (hopefully).

I also found that Losi converted to larger 3.5mm turnbuckles some time during the XXX's run, so I'm going to try and convert to that as well.

Back to the waiting game!

[RCveteran]

Ni ce work on fitting those 22 carriers. I bet those would sell if you wanted. They would be very handy trying to run a JRXT which has the goofy offset wheels. I'm trying to stay as close to vintage as possible these days but it's getting hard for sure if you want to run.

[HS-YZ250]

Ni ce work on fitting those 22 carriers. I bet those would sell if you wanted. They would be very handy trying to run a JRXT which has the goofy offset wheels. I'm trying to stay as close to vintage as possible these days but it's getting hard for sure if you want to run.

Thanks! Yeah, I'm excited for them and wondered if anyone else had a need. Thought I might put them on shapeways if they work well. The issues are they're designed around the LXT upright, not the Pro SE's since I have the Jammin' Steering Enhancement KIt, and they're not an exact match for that because the 22 knuckle takes up some of the space the upper ball would be. I'll have to see if I can place the stud in the "shadow" of the knuckle and play with using spacer combinations to make a part that can be set up for either LXT or Pro SE geometry.

[HS-YZ250]

I made a lot of progress this weekend, but am going to have to really think about wheels. I'll post the bulk later, but here's what the front end links look like right now. I think I have B4 hex conversion front wheels on there right now, which I needed to match the current width of the rear, but the hexes are too deep for the new front axles.

[HS-YZ250]

I've been sidetracked too much to put the final touches on the next iteration of the upright. In the mean time, my obsessive Googling skills paid off with an almost full set of threaded shock bodies and TiNi shafts, for not-inflated prices, from a few Michigan hobby shops/chains for both my Pro SE and LXT. Just missing one 0.6in shaft.

[Worldsman]

I had an Losi Pro Se , 15 years ago.
This was one of my Best rc cars i have ever had.
I sold it 10 years ago.

[HS-YZ250]

Aaaand I'm back!

Had a laptop burn out, then couldn't remember my login.

Anyway, here's what I've done since my last post:

I stopped for a moment to get a (lousy) image of the last electronics setup. Originally I had a Tekin 411P cable tied to the rear shock tower, but some years ago I popped a component on the board and found this 411-G2. Also I found a couple of the RPM speed controller mounts to try and get a cleaner and more secure chassis. But this time around I want to go brushless. Ideally I'd find a good reversible ESC that can fit in the side tub. Then I'll let my old brushed stuff go on to someone else.

After playing around with the front wheel options I decided to stick with the Losi wheels and print another iteration of the caster blocks that got the ball stud out from behind the kingpin. This resulted in a track width similar to the rear with the B4 wheels and hex drives. Not sure how this setup currently compares to the stock JRX PRO SE, I'll have to go back some time and measure, but I think I got closer to the LXT caster block geometry .

I took apart the transmission to clean and re-grease it for the first time since I put the chassis together. At this point I dug out a NOS rear bulkhead I bought a number of years ago to fix the loose h-arm pivot from a crash back in the mid 90's that's bothered me ever since.

By the way, thanks to whomever posted the XX retrofit manual because I immediately forgot how it went together. And also thanks for the Dual Slipper conversion. I allowed that bit of scope creep because I want the option to run this whenever I want but and I knew the hydra drive spurs aren't very easy to find, anymore.

While it was out I tapped the bulkhead and rear uprights for the new TLR22 ball studs and ran into an interference issue. The motor plate wouldn't let the larger tie rod end fit, so I had to break out the dremel and create a little clearance. Fortunately it didn't take much. I don't have an image, but I used a longer than normal ball stud on the bilk head with TLR22 spacers to try and get the rear camber links to be more parallel with the H-arms. This also meant had to do a small counter-boring on the bulkhead to let the TLR22 ball studs fully seat, as there's a small step that would interfere with the spacers.

I put all the suspension back together with the TLR22 and XXX ball studs and tie rod ends and did a rough setup. Eventually I'll need to get proper length 3.5 mm tie rods. But also I want to look into better tie rod ends. The TLR22 rod ends are much sloppier than I had hoped they would be, and steering slop is what prompted me to do this in the first place. I think I was using TLR22 3.0 or 4.0 tie rod ends. Are the 5.0 tighter? Or should I look at an aftermarket set?

I put the slop aside for now and went to work on re-mounting the servo. Especially on my LXT, I always hated how I had mounted it and wished to square it up. I did a better job on this buggy than I had done on the LXT, but I had used a small pan car servo saver and still mounted the servo skewed. I had to do buy a few servo savers to find one that fit the way I wanted, settling on a Axial part. I also modeled and printed new servo mounts that would hold the servo as close to the chassis plate as possible. I drilled a new set of holes, but still ended up not getting a perfect fit and alignment, but with a spacer under the ball stud I think it'll work. I'll re-evaluate when I get power to it. Might take a little strategic filing. If all else fails, Axial included a shorter servo horn.

So now I'm shopping for an ESC and motor. Here my choices aren't going to make the most sense as I'll be favoring style over substance.

I wanted to get a visually appealing motor, since that's what I remember about RC motors from the early 90's: brightly colored labels/cans hanging out of the back of the cars. Looks like, today, they're mostly black, I guess because they're hidden under the body when running. I also wanted a Trinity because Losi was teamed with Trinity , and Trinity was a pretty ubiquitous brand back then, even though I think a lot of others were better. I also wanted a little bit of heat, and I eventually found Trinity's D4 had a nice gunmetal can with an purple endbell, and came in a 13.5. Unfortunately I missed an auction for one, and another I was interested in was buried in a lot of motors that the seller wouldn't separate. So the search continues.

For an ESC I want two things: reverse and to be able to mount it on the chassis plate instead of the shock tower. The latter is a tough requirement: the pocket on the side of the chassis is less than 30 mm, and even the Kyosho Le Mans controller is just a couple mm larger than that. Looking around I found that current Tekin ESC's are available with reverse, and have widths available under 30mm. For the added nostalgia, I ran both my vehicles with Tekin controllers ever since I started racing, so that's appealing as well. Unfortunately, those controllers aren't cheap. So I'll look for a used on on eBay for a little bit before I look to buy one of those.

Also, I need to get to assembling these new shocks. Can anyone tell me if modern Associated or Losi shock fluid viscosities equate to 90's Losis? I'll be starting with the original JRX PRO SE Setup sheet unless someone has better suggestions.

[HS-YZ250]

Wasn't (yet) able to find a flashy enough brushless Trinity I wanted, but an auction popped up for this Losi branded motor, which is pretty neat. I would have liked the endbell to have been blue as well, but it'll do for now. Anyone know the history of these and who made them for Losi?

Just need an ESC, now, and I can put power to it, again, and see how much of a mess the front end geometry is.

[mikesofunny]

If you don't get the holes for the servo just right (as the previous owner of my LXT chassis did), you can use UV plastic weld to patch, then re-drill/countersink. It doesn't look perfect, but it works pretty well! I used Bondic brand. Here is the build thread.

As far as oil viscosities go, I'm pretty sure that hasn't changed over the years. 30wt is still 30wt, and so on and so forth. Hope some of this helps. Nice build!

I'd love to see your LXT, have a thread on it, or any pictures?

[HS-YZ250]

Got a Tekin RS in the mail, today! Threw it right in just to get power to the car for the first time, so wiring is a mess. It's dark, cold, and rainy right now so just aligned the steering and scooted around the carpet a bit. Quite exciting! Has a really tight turn radius. But don't really have a feel for handling.

Need to tune and teak a bunch of things. The Tekin, unfortunately, while it is close, is just a hare too big to fully sit down in the side pocket of the chassis, thanks to the draft on the chassis ribs. I think I'll model and print a holder to sit it at an angle, though it's so small I might consider up around the rear shock tower, again.

I'm already missing the black/gold the vintage Tekin had so, I was wondering: did I see that someone here makes vintage labels for modern electronics? If so, that might have to happen once I get it positioned

I'd love to see your LXT, have a thread on it, or any pictures?

I don't have anything for my LXT, yet. But here it is. I did probably 90% of my racing with this, 9.5% with my Pro SE, and 0.5% with my Rocky. (Rough numbers. Lol!) It started as a JRX-T, raced the stink out of it, then got the Losi conversion kit to turn it into the LXT after everyone got the RC10T at my track. Always raced Stock Truck, rarely won. When I'm done with the Pro SE I'll see if I can do the same mods with this. Depends on if I can find wheels and hex drives. Thanks for the shock fluid info! The threaded shock bodies are next!