A hot motor could be caused by gearing that is too low too. If you are maxing out the throttle a lot (winding the motor out for long periods), then it will get warm/hot.

But if geared "right" a decent motor that runs hot could mean partial rotor demagnification.

Thing is, the stock flux is lighter than your custom flux, and it comes with a 1515 2200kv motor; on 6s lipo with stock gearing 55-60mph is about top speed roughly, and even then thats an on-road kind of setup, 60mph offoad would be pretty much uncontrollable over about 50% throttle. Your truck is running a larger, more powerful motor yes, but its a much lower kv, and the voltage is the same, so gearing it for higher speeds than the stock flux places a much larger strain on all the electronics, hence the high temps. The 1520 and 1717 are great motors for heavier weight vehicles running the same speed as lighter vehicles that use higher kv motors. For example, my 1518 1800kv motor ran nice and cool on 5s lipo in my 13.5lb TXT-1, but my 1515 ( ish) sized medusa 2000kv motor runs somewhat hotter in my 13lb Gorillamaxx on 5s lipo too. The Gmaxx is geared for 40mph, the TXT-1 for ~35mph- if I wanted to run either truck faster I'd go for 6s & a 1518, and aim for about 50-55mph tops- keeping my speeds and expectations realistic...

Knowing whats realistic and why comes with time, and lots of research/reading around to learn from other's experience. That said, you're in the right place for certain; Rc-Monster is known as 'The Encyclopedia Brushless' :yes:

neil.. thanks for taking your time to explain this to me... It really has put things in perspective... I tried doing my reading and asking people what would be an ideal motor that would meet my expectations. I guess i am pushing it a little too high.
I was originally wanting to go for the 1518 but due to having no motor at the time and no 1518 in stock anywhere... i went for the 1520.
I have a few gearing options... I will chuck my 17t clutch bell in there first... with the rc calculator it will bring the top speed down from 75mph (very unrealistic, i wasnt even aiming for these speeds) to 60mph... if its still running too hot. I will take out the the high speed idler gear and put the stock one back in and run the 21t pinion which should gear me for around 50-55mph... I will just watch my temps and gear accordingly.

I am going to work out a way to try and cut weight on my truck... At the moment its only weighing 1 ounce heavier over stock. each wheel is 10gram heavier and the tvps weigh only very slightly over stock. Thats the only weight i have added. (maybe the motor too)

Anyway i really appreciate your help! I will get back to you and tell you what happens.

THANKS!

Hmm, I thought it was heavier than that, but anything you can do to save weight is always a plus, regardless. I tend not to follow all my own advice though; my tyres weight 1lb each on my TXT-1 :lol:, but I have gone to lighter ones for my Gmaxx- have yet to see how that performs though.

neil i weighed the truck today... and with my wheels and tires and depending on what batteries i am using the weight is 13.1- 14.2lbs.

THAT IS LIGHT FOR A LARGE TRUCK!!! BUT at its heaviest with the large wheels, and large batteries and heavy body... it reaches 17lbs.

I will keep you updated on how it runs with the 17t clutchbell.. .I hope it doesnt cause any more heat problems.