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Old 01-21-2012, 02:35 AM
recon chris's Avatar
recon chris recon chris is offline
Motorized Bicycle Senior Member
Join Date: Apr 2011
Location: pacific grove
Posts: 87
Default Re: Getting all 3 Horse Power out of your GT-5 Sky? (tear down)

After tearing the engine completely down and examining it I can honestly say no, not one bit. The way it should harm the engine is by adding extra heat to the jug and the piston. 400 miles later I can honestly say that there is not engine damage due to over backpressure. At first I didn't port the exhaust and it came with the standard "Hole". The engine carb had to be tuned just perfect to get it to run right. Once I semi ported the exhaust pipe to improve flow and lower initial back pressure it became allot less finicky and rode just fine. However the standard EPA exhaust has an end cap and if you take it off you get about another 66cc worth of low end power. You will be able to see it in the pictures what I’m talking about.

pic of original exhaust

The Catalytic converter in exhaust behind the plate with 5 holes in it (can you say restricted air flow)

What I did to the exhaust pipe port

The beginning of the new exhaust that will have only the expansion chamber for precise back pressure, I’m using a 1 inch pipe for the header

Side by side Old and New

Last edited by recon chris; 01-22-2012 at 04:25 AM.
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