I made a tricopter with KK2.1.5 as the FC but I have encountered a problem. The tricopter starts rotating before take off. All the sticks have been centered still the copter rotates. Here's a video. Any help is welcomed! 

Few things to look at(not sure it will help)-
Select correct servo output hz, in kk2 setting, 400 digital or 50 analog.
Tilt servo should be tilted By few degrees (left or right not sure).
Make sure zero vibrations are there in tail motor.
I could not solve my problem of spinning before take off with David style tail, I made a bent metal link and mounted servo below boom. used kk2.0.


Add- make sure fc is giving correction in right direction.

Thank you pravesh sir for the quick reply. I will try your suggestions and update it over here! Thank you once again! 

Problem solved!
Solution:
Changed the frequency to low(50 Hz) as pravesh Sir pointed out.
In the Mixer option on ch 4(the Servo port) changed the rudder value from 100 to -100(saw it on RCG. The guy had the same problem as mine)
The tilt and the servo had some slack so tightened it.
And now it flies better than before. 

Did you identified ONE the cause from above two corrections? Or, both were the issues causing the yaw problem.

Hello Piyush,
Both the things had to be applied to get the copter working right.

i think servo filter should be reversed.
I had same problem and i just reversed servo filter in mixer-editor .

Hi.i have also made a tricopter recently and am facing similar problems.
1.it starts to rotate on increasing throttle.
2. It tends y o flip over towards the front side just before take off.itried to trim the elevator control but no major benefit.
3. The servo oscillates.

Please help veterans.

Rusty if your using KK2.x.x board simply change the frequency to low(50 Hz) if using analog servos else keep it high(400 Hz)
In the Mixer option on ch 4(the Servo port) change the rudder value from 100 to -100
This should solve your problem!

@Rusty sir,

1. Check all the above discussed things.
2. May be CG need to be adjusted, Currently its more in the front side and need to push it to backwards(towards the yaw), please post a pic/video.
3. Occilates while landed? That's normal, check when that happens while off the ground.

A bit off the actual problem: Is this a tricopter? 

Is everyone seeing the extra 2 motors or its just me or is there a new trend evolved which i am not aware of?

But the copter looks sturdy and light. any idea on the grade of aluminum used and the total weight of the copter?

I made one and it weighed just over 1500gms with a DT750 motor!!!

v2 eagle thats wired like a tricopter, but technically a pentacopter... 2 motors on each side are treated as one...

Ashok sir it is a normal tricopter the extra two motors are just for the extra lifting capacity and added redundancy(the copter can still keep flying even if 2 motors fail(not the tail motor!) as the FC knows there are only 3 motor to be of concerned of!).
The signals to the front motors are Y'd to the 2 motors.
My copter weighed 1.6Kg with 3.3Ah 3S battery!

Thanks for the info both of you. Lucky you that you get 5 arms and 3.3ah for 1.6kg.

thanks for the replies.will try it for certain.

this is my home built tricopter which is having trouble.please have a view and give suggestions.

Would be great if you cud gove wat exactly the problem is...

The main problem is that it behaves very erratically. Some time motor 1 is running faster. I trim channel 1 and then the motor 2 (rudder) starts running faster.i control it by trim and again the servo misbehaves.

Did you tried taking it off the ground and see if this issue is still there. a copter still on the ground will give all sort of issues and disappears magically when the copter is on air.

and are the motors capable of lifting the copter weight?

I think it's the yaw  thing that you want to solve
Try this
Go to the channel 4 setting and then change the value from 100 to -100

What type of servo are you using rustydusty? Analog or Digital?

Its a tower 9gm servo.i think its analog.

The torque may not be enough for holding the motor steady. And it is an advice not to use plastic geared servo as they fail quite often and the tail being the most important part of the tricopter too.
If you are using kk.2.x.x fc then change the frequency to low for the servo in the misc settings as its is an analog servo!

I have already done that. Its in low rate.

So its still yawing like in the video?