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Discussion Starter · #1 ·
So here's the deal. I'm brand new to this site and from all the searching I have done I found this site to be the most informative. I have recently got ahold of a 1980 cx500custom and when I got it the exhaust was missing, all it had were the headers. I have mocked up about 2 1/2 feet of 1 1/2 inch exhaust pipe on either side. I am in the process of cleaning the bike up so I haven't ridden it yet but I have fired it up and ran it a bit. The left cylinder doesn't fire on idle but it will fire when I turn the throttle and after I shut the bike off the left exhaust pipe I can touch my hand to but the right side pipe is a scorcher. So I have ordered new carb kits and I am going to rebuild the carbs but while I have them apart I was curious if I was going to need to rejet them with the straight pipes with no h-box. I didn't know if anyone on this site is running straight pipes with original airbox, and if so what size jets are you running. Any help or suggestions would be greatly appreciated.



Thanks,

Trev
 

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You may need to rejet, the backpressure will be less without the H box and mufflers. Personally, I would shop for some OEM exhaust parts and put it back the way Honda intended. The noise level will be high without the box and mufflers. You know what they say, "Loud pipes irritate lives".
 

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So here's the deal. I'm brand new to this site and from all the searching I have done I found this site to be the most informative. I have recently got ahold of a 1980 cx500custom and when I got it the exhaust was missing, all it had were the headers. I have mocked up about 2 1/2 feet of 1 1/2 inch exhaust pipe on either side. I am in the process of cleaning the bike up so I haven't ridden it yet but I have fired it up and ran it a bit. The left cylinder doesn't fire on idle but it will fire when I turn the throttle and after I shut the bike off the left exhaust pipe I can touch my hand to but the right side pipe is a scorcher. So I have ordered new carb kits and I am going to rebuild the carbs but while I have them apart I was curious if I was going to need to rejet them with the straight pipes with no h-box. I didn't know if anyone on this site is running straight pipes with original airbox, and if so what size jets are you running. Any help or suggestions would be greatly appreciated.



Thanks,

Trev


I do know the jets were finely tuned to match the stock intake and exhaust, even changing the air filter to a K&N seems to upset things a bit.



You'll probably need to go to 90/120 jets with straight pipes. Quite honestly I think you'd like it better if at the very least you put some Harley mufflers at the ends of those pipes, they can often be found rather cheaply if you look hard enough.
 

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Discussion Starter · #4 ·
Thanks for the input on the numbers. I will get the carbs all rebuilt and do a jet swap and see how it sounds. If it's obnoxiously loud I will have to add some sort of muffler like you are saying. I've got a buddy I can probably get a set of shortys from if I need to. Anyone else have any input on the possible jet size? 90/120 was kind of what I was leaning towards after scouring the internet on what people have come up with after doing exhaust mods.
 
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