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viper copperhead

Viper Copperhead and VX4.39 Sensorless Brushless Motor/ESC System Review

THE Viper Copperhead and VX4.39 Sensorless Brushless Motor/ESC System Review

viper copperhead

A few weeks ago we reviewed the latest 550 brushless system from Viper, this week we’ll be taking a look at it’s slightly smaller brother, a Viper intended for your 2wd tenth scale SCT. The Viper Copperhead speedo and VX4.39 motor system are an affordable option for your 2wd SCT, how does it stack up? Let’s find out…

From: Viper R/C Solutions
Direct Link: Viper VX4 Copperhead R 550 system

Reviewed by:Cubby.
Pics by:Cubby.

System Part #: 6VSVX43901
Street Price: $150

Speedo Specs:

Continuous/Burst Current- 100/550A
Footprint- 45.5 x 39.8 x 29.3 mm
BEC- 6 volts/5 amps Linear
On Resistance- .0009 ohm * 2
Cell count- 2 to 3S Li-Po
Motor Limit- 2S 540 Less than 6,000 Kv, 3S 540 Less than 4000 Kv
Sensored- No
Default Profiles- 5
Fan- Yes
Warranty- 180 Days

Motor Specs-

Size- 540
Length- 2.08″
Diameter- 1.42″
Sensored- No
Max Cell Count- 3S
Max Temp- 180 F
Kv- 3900
Poles- 4
Output shaft- 3.17 mm
Weight- 7.72 oz
Warranty- 180 Days

What’s In The Box: Viper Copperhead speedo, VX4.39 motor, stickers, speedo manual, gearing chart, double sided tape

Build Quality: Not as uber looking as some of the higher end Viper product, but still looked solid.

Test Drivers: Cubby, Brian, Iron Mike

Test Venues: RC Outlaws in Collinsville Illinois, Costco parking lot, streets of a local sub-division, grassy backyard

Set-up Notes: Test truck was a ECX Torment. For gearing we utilized the stock pinion and spur. We only used MaxAmps 2S 6500 Race Spec packs during testing. The Torment was pretty much bone stock except for a Sunshine Systems lighting kit.

Ease of Use: Calibrating the speedo to our radio gear was a snap after reading the manual. Not the easiest speedo on the market to set-up, but very close.

Drivability/Feel/Powerband: The powerband on the Viper Copperhead felt similar to that of the Copperhead R that we reviewed a few weeks ago. You have dead stop, or 1 mph, but nothing in between like you would have on a sensored Viper system, so there is a bit of a lurch leaving from a dead stop. From there on up the powerband of Copperhead seemed a bit smoother than its bigger brother. Low end was still a bit soft, but overall the powerband on the Copperhead plus 540 system seemed more linear than the Copperhead R 550 system, likely due to differences in the motors involved. Reverse engaged without issue and was set to a reasonable power output, and going from throttle to neutral to reverse was quite smooth for a non-sensored system.

Thermalling: We didn’t push our Copperhead system on 3S, we only ran it on 2S, and the typical ambient temps while testing were around 60-80 degrees Fahrenheit. With that said we had no issues with the speedo getting too hot and shutting off, in fact our Copperhead speedo ran very cool, rarely getting over skin temp. The highest I ever measured the speedo was 105 F. The VX4.39 motor ran hotter than speedo with the highest reading I saw being 132 degrees F.

Cogging: We did not experience any cogging with our Viper system. I purposely tried to make it to cog by starting it repeatedly on an uphill, but even that didn’t make it stutter one bit. The Viper would lurch from a dead stop to its minimum drive speed, but never cogged.

Power: We didn’t gear our VX4.39 to the moon, nor did we run it on 3S, so no we didn’t go for crazy power on our review system. We dropped it into our ECX Torment like thousands of normal bashers would, stock gearing and all. What we saw was a tremendous increase in power over the stock brushed system that comes in the ECX. The Viper provided tons more power from bottom to top. The Viper 540 system had more than enough grunt to yank the front tires off the ground from a dead stop and much greater top speed than stock. On track the Viper was shooting our Torment over all the doubles the 8th scales were making with no problem. Btw, nothing puts a bigger smile on our face than keeping up with nitro 8th scales with a truck that costs hundreds less.

Brakes: The brakes on the Copperhead felt much like those on the Copperhead R we just tested- a bit soft with stock programming, even for low bite surfaces. When slamming on the brakes in an “Oh Crap!” situation we couldn’t lock up the tires, even on a fairly slick dirt off road track. Luckily the brakes are easily adjusted for more stopping power.

Fit: The Viper Copperhead isn’t a tiny speedo, nor is it large. We had no issues fitting it in our ECX Torment, and it should fit easily into any 2wd SCT. The motor is a standard 540 that fit perfectly in our Torment and will fit perfectly in pretty much any 2wd SCT or tenth scale electric vehicle.

As with all of our stuff, if you see us at a bash, stop by and check out the vehicles we have with us. We may let you take a test drive, and at the very least get you some stickers!


Time To Bash – 9/10 -The speedo came with a Deans soldered up and the motor came with bullets soldered on. The Viper installed quickly for a BL system.

Car Show Rating – 8.0/10 – Nice clean look on both the speedo and motor.

Bash-A-Bility – 10.0/10 -We bashed our Torment for weeks with no issues on the Viper, even the fan still works!

Fun Factor – 8/10 – The Viper turned our rather tortoise like Torment into a rock spewing bash machine, so of course big smiles ensued.

Drivability -8.0/10 – We found the Viper 540 system to have an easy to drive low end with a fairly linear powerband, very nice for a non-sensored unit.

Power- 8/10 – The Viper has good power on tap with just a 2S Lipo battery and tame gearing.

Value- 9/10 – $135 isn’t the cheapest brushless system out there, but nor is it even close to being the most expensive. The Viper offers a lot of bang for your hard earned bucks.

Big Squid Rating – 8.5/10 – Tentacles.. – No doubt there are a LOT of choices out there for your 2wd SCT, however the Viper is a solid choice at a very attractive price point. During our weeks of testing we didn’t experience one issue with the Viper, it took our abuse and kept on ticking. It’s easy to program, easy to install, and it will make a very nice brushless system for your short course truck.

Don’t forget to check out the VX4 550 review.

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Posted by in Accessory Reviews, Viper RC on Thursday, April 5th, 2012 at 8:39 am