My JRX-Pro period runner.

[8rad]

As often happens I did not document this build so here is the almost finished car. It runs pretty well but needs a few more things. Decals, slipper and a decent set of wheels and tires for starters.

My concept for the build was to create a runner how it may have appeared back in 1991/92 but with some modern upgrades to help with maintenance and durability. It was also the perfect opportunity to use one of the many magnum sport radios we all seem to accumulate but never use.

I wanted to keep the stock feel but I did not want to go totally 1991 stock because the stock Pro had some definite shortcomings.

The shocks got Ti shafts, wide spring collars, rebuildable cartriges and powder coated springs.

Stock steel turnbuckles were replaced in favor of Lunsford Ti and RPM ball cups. These were the first things to go BITD because the stock steel turnbuckles were soft as butter.

For electronics I used a Tekin Mosfet speed controller which I modified to three wire and TERX 75 receiver. Battery is SMC matched 2000SCRC's. The SCRC's apperared after the Pro was in its glory but until I find some 1400SCR's this pack will have to do. Motor is a Twisters Scorpion stock motor.

After running it up and down the street one thing became obvious. Everything I have read about Tekin speed controllers brakes is true. Absolutely brutal! I think braking distance from full was about 20 feet! Maybe the braking fet is blown or something.

[Charlie don't surf]

Wow, hard to believe you are running that ESC!

[8rad]

HEHE...Yes it is pretty old. I am on the lookout for something a little better but I like the fact it is red! Interesting though when I opened it up to do the three wire conversion I noticed the circuit board said KO on it!

[Coelacanth]

Nice attention to detail, that's a pretty car there. Love the red bits and the body painted to match!

[8rad]

Thanks. I am really happy with the paint. I think I will have to ditch the front red springs though. It turns like a semi even on the street.

[RedScampi]

Really nice looking car! You could paint a set of appropriate springs red to retain that look...

[8rad]

Really nice looking car! You could paint a set of appropriate springs red to retain that look...

Great idea! Did the Pro come with soft springs on the front? I think the reds are considered Medium are they not?

[tim.sanderson]

Some springs are even dyable. I know a guy who used to dye all his springs black. I'm not sure what make of springs they are/were, though. I think whatever coating was on the springs can take a dye. I'll ask him next time I see him.

[Jirka]

Really nice looking car! You could paint a set of appropriate springs red to retain that look...

Great idea! Did the Pro come with soft springs on the front? I think the reds are considered Medium are they not?

Red were the softest losi sprins at that time. Standard springs are silver and they are one step harder than reds. Front shocks were normally on outermost hole in tower and inner hole in arm.

Jirka

[Charlie don't surf]

Different red springs than what you have though

[8rad]

When they started with the powder coating pink was the softest. Maybe I'll hunt down some original reds.

[huminski]

Real nice car, well done. The paint is extremely classy. Needs some vintage decals on it. (you said that)

Nice work.

[Charlie don't surf]

When they started with the powder coating pink was the softest. Maybe I'll hunt down some original reds.

There are or were some on ebay recently, the old translucent red chrome-

[8rad]

Front shocks were normally on outermost hole in tower and inner hole in arm.

I just re-read this thread and noticed this. I may try this first before embarking on a spring hunt.

Thanks Jirka.

[Jirka]

Front shocks were normally on outermost hole in tower and inner hole in arm.

I just re-read this thread and noticed this. I may try this first before embarking on a spring hunt.

Thanks Jirka.

Some other setup thing come to my mind:
- Normally rear pivot support no 1 was used. This gives maximum rear toe in (6-degrees) and also maximum rear anti squat (4-degrees).
- Install rear H-arms so that the arrow on the bottom points to front.
- Front shock oil was lighter than "normal". Losi even had 5wt oil, but something like 10-20wt might be good. You might also drill piston holes bigger.
- JrxPro was very sensitive about rear shocks, springs and shock mounting holes. You could try something like 40wt oil and standard not drilled pistons to rear shocks. Try to play with shock mounting positions and start with outermost hole in H-arm and top could be placed depending of the track where needed. I, if remember correctly, normally placed the top of the shocks on the top row innermost or outermost hole. You could also try stiffer rear springs than red (springs from soft to hard during JrxPro time were: red, silver, green and dark blue/purple. Then there was black spring that was progressive). I did use normally red springs on front and back.
- Be sure that diff works smoothly
- Fine tune steering by playing toe in / toe out setting, depending of the track.
- Your servo saver might be too soft. Is that Schumacher part? Try Kimbrough's heavy duty or big servo saver. That is why there is hole below the servo saver in chassis so You could use them and only them. You might need to file chassis to make even more room to servo saver. Other way (and in this case, since your chassis is in relatively good shape, more acceptable) might be to place some servo size sheet between chassis and servo to rise the servo a little. I think changing servosaver is a must before You try anything else.

Read setup tips from some of the last pages of the JrxPro manual, they are really good.

Jirka