Im not sure your doing the test properly. The numbers you got were not bad...not great either. 160-180 is what I would be looking for.  The way I always did a compression test was... 
Warm the engine up completely. 
Remove plug and ground the wire  
Install compression gauge 
Hold throttle wide open 
And kick until the gauge  stopped rising 
Now I have never done a test on trials bike before...just MX bikes, so my numbers may be wrong.