Remove cat from TT 250?

Sclark1013 · 07-20-2018, 12:01 PM

There have been posts talking about removing the cat on the Hawk and/or TT250. Forgive my ignorance, but why do I want to do this? Will I really see more power, smoother idle, etc.. If I remove the catalytic convertor from my muffler, will I need to do anything else? Re-jet the carburetor, etc??? Your thoughts greatly appreciated!

ChrisWNY · 07-20-2018, 01:24 PM

The catalytic converters are restrictive and get jammed up eventually...they rob power from your Hawk/TT250 and cause the engine to run hotter. The same is true for the carb - Hawks have #98 main jets stock/OEM, which causes the engine to run leaner and hotter. Changing the main jet to a #110 and opening up the exhaust (with an appropriate aftermarket exhaust) will both improve performance and allow the engine to run cooler/breathe easier. The TT250 I believe has a larger main jet and slightly less restrictive exhaust so it should be better to run stock vs. the Hawk.

roundhouse · 07-20-2018, 06:15 PM

When I changed the exhaust and from a #110 to a #120 jet. I found my bike did have more power. It is not like a kick in the pants faster but my bike revved quicker and runs smoother.

Chris got it right about running cooler too. I assume the motor is cooler but the exhaust is significantly cooler.

Don;t forget the big bonus. It sounds GREAT!

07-20-2018, 01:24 PM	#2
ChrisWNY Join Date: Jul 2018 Posts: 212	The catalytic converters are restrictive and get jammed up eventually...they rob power from your Hawk/TT250 and cause the engine to run hotter. The same is true for the carb - Hawks have #98 main jets stock/OEM, which causes the engine to run leaner and hotter. Changing the main jet to a #110 and opening up the exhaust (with an appropriate aftermarket exhaust) will both improve performance and allow the engine to run cooler/breathe easier. The TT250 I believe has a larger main jet and slightly less restrictive exhaust so it should be better to run stock vs. the Hawk. __________________ 2018 RPS Hawk 250cc Mods so far: 1. Mikuni VM26 Carburetor w/#115 main jet 2. 17T/45T JT sprockets 3. JT 428 X-ring chain 4. Air box mod 5. Hawk Digital Cluster 6. Aftermarket IMS shift lever 7. Performance Aftermarket Exhaust 8. 295mm Nitrogen Gas Monoshock, 20W oil front forks
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07-20-2018, 12:01 PM	#1
Sclark1013 Join Date: May 2018 Posts: 41	Remove cat from TT 250? There have been posts talking about removing the cat on the Hawk and/or TT250. Forgive my ignorance, but why do I want to do this? Will I really see more power, smoother idle, etc.. If I remove the catalytic convertor from my muffler, will I need to do anything else? Re-jet the carburetor, etc??? Your thoughts greatly appreciated!
	1

07-20-2018, 06:15 PM	#3
roundhouse Join Date: Sep 2017 Location: N Texas Posts: 706	When I changed the exhaust and from a #110 to a #120 jet. I found my bike did have more power. It is not like a kick in the pants faster but my bike revved quicker and runs smoother. Chris got it right about running cooler too. I assume the motor is cooler but the exhaust is significantly cooler. Don;t forget the big bonus. It sounds GREAT!
	2