Drilling out gy-5 exhaust
 

I see a of people here are doing mods to the gy-5 muffler like drilling holes at the back. Does this really give better performance or is it just to make it sound better. And, what about emissions? Can you still pass emissions/inspectoin test if you are streel legal in those states that require them? I know MD, and PA have emmissions tests.

I dont know if it helps performance at all but there are several threads that speak about potential performance increases but like any exhaust mod you will get the most benefit when you address induction as well (car and Air box/cleaner)

Now for the bad news...Im from NJ and there is no doubt in my mind that when you go for inspection , of they see multiple holes drilled out chances are you will fail automatically. Id leave it stock, get emissions passed....then drill out diameter of the stock exhaust hole... or better yet like others have done.....cut off the back half of the muffler, pull out all baffles, re-weld back end on and open up diameter of stock exhaust exit hole.

Im sure there are others on here with first hand expereince.

I've done both and the baffle removal is only a marginal improvement. So, for the time it takes I'd just drill do the filter and carb mod and be done with it.

Jason

I don't know much, but I did do the MOD. The way it was explained to me was, if you change your air filter you'll get more AIR in. Messing with the carb gets more FUEL in. Drilling the muffler gets more exhaust OUT. From Whizzers to Tomos mopeds, most owners of small engine bikes do the same mod to get more throughput.

At idle and low revs my bike's noise is the same as before the mod. When I gun the throttle, I admit the muffler does not muffle the way it used to. As for the emissions part, if my bike is still alive when I have to do my next test 8O I have no problem buying a new muffler to use for the day. :D

N2r 150 Xingyue