Disappointment after removing the catalytic converter

Larky · 04-24-2020, 10:27 AM

Hey guys,
As the title states, I’m not sure I’m happy with the outcome of removing my catalytic converter off my tbr7. I feel as if I’ve lost low end torque. I increased the main jet to a 115. Also ground down the weld at the connection to the head. Looking for suggestions to get it back. I understand the answer might be to get a stock header and leave that cat alone. Let me know what you think.

bogieboy · 04-24-2020, 10:33 AM

might need a bigger pilot jet... more flow across the board means you may need more fuel across the board as well...

**JerryHawk250** · 04-24-2020, 10:47 AM

Quote:

Originally Posted by bogieboy

might need a bigger pilot jet... more flow across the board means you may need more fuel across the board as well...

^^^What he said. ^^^ X2 Removing the cat definitely woke up my hawk.

Larky · 04-24-2020, 11:05 AM

Great! Thanks guys. Is there anything else I should do after the pilot jet? I’m at about 1000-1500 feet above sea level. Just to convey all info, I’ve shimmed the needle jet up one washers thickness. Maybe add a second washer?
Thanks again guys.

Kenstogie · 04-24-2020, 02:41 PM

Quote:

Originally Posted by JerryHawk250

^^^What he said. ^^^ X2 Removing the cat definitely woke up my hawk.

HUGE difference for me putting on that new exhaust...

what can you do on a tbr7 ( pod?) for the air intake side.......

and how much gain?

alex_in_az · 04-24-2020, 04:10 PM

Quote:

Originally Posted by Kenstogie

HUGE difference for me putting on that new exhaust...

what can you do on a tbr7 ( pod?) for the air intake side.......

and how much gain?

the intake side is OK on the TBR, once you've done the mods to the carb. I'm just about ready to put a PnP head on my TBR, I had to remove a lot of material from the exhaust port, there's a big lump right by the ex valve that needs to go and on the top side of the port as well. In contrast I hardly did anything to the intake port, because it looked pretty good as is. I decked it .040 as well, so my CR should be around 10.3 if my math is correct

Megadan · 04-24-2020, 04:26 PM

Quote:

Originally Posted by alex_in_az

the intake side is OK on the TBR, once you've done the mods to the carb. I'm just about ready to put a PnP head on my TBR, I had to remove a lot of material from the exhaust port, there's a big lump right by the ex valve that needs to go and on the top side of the port as well. In contrast I hardly did anything to the intake port, because it looked pretty good as is. I decked it .040 as well, so my CR should be around 10.3 if my math is correct

Sounds like my head lol.

2LZ · 04-24-2020, 12:08 PM

Like previously mentioned, the pilot jet.....but if you haven't lifted the needle a notch yet, that may also help.

kingofqueenz · 04-24-2020, 01:24 PM

No expert...

Isn't the theory "air in ...air out"

Thought I read, the airbox mod on the Hawk does not work on the TBR

Did you mod the air in portion of the equation?

Larky · 04-24-2020, 01:35 PM

Quote:

Originally Posted by kingofqueenz

No expert...

Isn't the theory "air in ...air out"

Thought I read, the airbox mod on the Hawk does not work on the TBR

Did you mod the air in portion of the equation?

Great question! But the answer is no. Didn’t touch the air box. I was under the impression that it wouldn’t add much power. Besides I like the air box / filter combination, especially if there was minimal-to no power gains. Although let me know guys I you felt that an air box mod was worth it.

Megadan · 04-24-2020, 02:07 PM

Quote:

Originally Posted by Larky

Great question! But the answer is no. Didn’t touch the air box. I was under the impression that it wouldn’t add much power. Besides I like the air box / filter combination, especially if there was minimal-to no power gains. Although let me know guys I you felt that an air box mod was worth it.

On its own modding the airbox doesn't result in much because the factory exhausts are restricting the engine enough that the gain is almost imperceptible. When done in support of an exhaust upgrade it can make a difference.

Rocket tests · 04-24-2020, 01:55 PM

Removing the baffle plate from the stock muffler helped mine breath a lot better.

Rocket tests · 04-24-2020, 08:27 PM

I can say that the port n' polish n' decking is well worth the time it takes. Night and day difference. The biggest drawback on mine is the starter often struggles to overcome the extra compression. I can count on needing to hit the starter button several times before it turn over without stalling the starter. Possibly could be resolved with a stronger battery.

One mod inevitably leads to the next and so on.

Megadan · 04-24-2020, 09:52 PM

Yes, you need a good strong battery if you increase the compression a full point, and if your battery is weak for some reason, you will find out after the first couple of turns.

That said, if you get the idle mixture and pilot jet sizing right, usually it only takes a couple of turns for the bike to start. Usually my bike will fire up right after the second revolution.

IMHO the increased compression, while it definitely adds a bit of oomph to the equation, could also be left out, or at the very least left to a small increase. Opening up the exhaust port and smoothing out the intake as myself, jerry, and obviously a few others have done, makes a big difference in how these engines perform.

Increasing the compression also leads to stronger vibrations, so be aware of that side effect too.

Rocket tests · 04-24-2020, 10:34 PM

It's amazing, with every mod I make my hair grows fuller and shinier, I can bench press double my previuos weight and my man hood..... well lets just say my wife isn't complaining.

04-24-2020, 10:27 AM	#1
Larky Join Date: Apr 2017 Location: Watkins Glen new york Posts: 69	Disappointment after removing the catalytic converter Hey guys, As the title states, I’m not sure I’m happy with the outcome of removing my catalytic converter off my tbr7. I feel as if I’ve lost low end torque. I increased the main jet to a 115. Also ground down the weld at the connection to the head. Looking for suggestions to get it back. I understand the answer might be to get a stock header and leave that cat alone. Let me know what you think.
	0

04-24-2020, 12:08 PM	#8
2LZ Join Date: Mar 2010 Location: Volcano, Ca Posts: 7,085	Like previously mentioned, the pilot jet.....but if you haven't lifted the needle a notch yet, that may also help. __________________ "Light a fire for a man, and you heat him for a day. Light a man on fire, and you heat him for the rest of his life." 2007 Suzuki DRZ400S (SM convert) 2009 Q Link XP 200 1967 BSA B25 250cc Starfire 2022 Royal Enfield Interceptor 650 2023 Royal Enfield Scram 411 1948 Royal Enfield Model G 350
	0

04-24-2020, 09:52 PM	#14
Megadan Join Date: Apr 2017 Location: Omaha, NE Posts: 8,008	Yes, you need a good strong battery if you increase the compression a full point, and if your battery is weak for some reason, you will find out after the first couple of turns. That said, if you get the idle mixture and pilot jet sizing right, usually it only takes a couple of turns for the bike to start. Usually my bike will fire up right after the second revolution. IMHO the increased compression, while it definitely adds a bit of oomph to the equation, could also be left out, or at the very least left to a small increase. Opening up the exhaust port and smoothing out the intake as myself, jerry, and obviously a few others have done, makes a big difference in how these engines perform. Increasing the compression also leads to stronger vibrations, so be aware of that side effect too. __________________ Hawk Information and Resource guide: http://www.chinariders.net/showthread.php?t=20331 2018 Hawk 250 - Full Mod list here. http://www.chinariders.net/showpost....62&postcount=1 2024 Royal Enfield Shotgun 650 https://chinariders.net/showthread.php?t=34124
	2

04-24-2020, 10:33 AM	#2
bogieboy Join Date: May 2013 Location: finger lakes NY Posts: 2,045	might need a bigger pilot jet... more flow across the board means you may need more fuel across the board as well...
	1

04-24-2020, 11:05 AM	#4
Larky Join Date: Apr 2017 Location: Watkins Glen new york Posts: 69	Great! Thanks guys. Is there anything else I should do after the pilot jet? I’m at about 1000-1500 feet above sea level. Just to convey all info, I’ve shimmed the needle jet up one washers thickness. Maybe add a second washer? Thanks again guys.
	0

04-24-2020, 01:24 PM	#9
kingofqueenz Join Date: Apr 2019 Location: Strong Island New Yawk Posts: 464	No expert... Isn't the theory "air in ...air out" Thought I read, the airbox mod on the Hawk does not work on the TBR Did you mod the air in portion of the equation?
	0

04-24-2020, 01:55 PM	#12
Rocket tests Join Date: Mar 2020 Location: Pennsylvania Posts: 87	Removing the baffle plate from the stock muffler helped mine breath a lot better.
	0

04-24-2020, 08:27 PM	#13
Rocket tests Join Date: Mar 2020 Location: Pennsylvania Posts: 87	I can say that the port n' polish n' decking is well worth the time it takes. Night and day difference. The biggest drawback on mine is the starter often struggles to overcome the extra compression. I can count on needing to hit the starter button several times before it turn over without stalling the starter. Possibly could be resolved with a stronger battery. One mod inevitably leads to the next and so on.
	1

04-24-2020, 10:34 PM	#15
Rocket tests Join Date: Mar 2020 Location: Pennsylvania Posts: 87	It's amazing, with every mod I make my hair grows fuller and shinier, I can bench press double my previuos weight and my man hood..... well lets just say my wife isn't complaining.
	2