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Hi all, I am thinking of buying a Carpy 4-1 for the 1981 cb750k, and just wondering whether I will need to change the jetting from stock? I have read may different things, and would like to get this cleared up. I am not running pods or have any engine mods.
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Administrator
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If by any chance you are, or know a physicists you might be able to do the math, and figure it out. However as I'm sure you have found in your research; every bike is different and you will just have to put it on and take plug readings to know for sure.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."
1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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If you are only changing the exhaust and no modifications to the stock airbox ,all you may need is a adjustment to the mixture screws to make them richer.
BTW....The Carpy exhaust may need to be completely removed to do a oil filter change.
Better check that out.
On a Roadstar Adventure.
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Alright, that would be nice! Yeah, the exhaust does need to come off for the oil filter change, but I'm putting a new one on the bike before I put the exhaust on so it should be ok for a while...do you have any experience with the carpy exhaust? Is it super loud, even with the baffle in?
-sean
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NAML
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All of the 4 into 1 exhausts have a little bark to them when opened up.
You can get a all metal baffle for them.
Do not get the fiberglass packed style because it blows fiberglass fibers all over the place and you will end up breathing those little pieces of glass.
You can see it it the sunlight when you rev up the bike with that fiberglass packing.
With a baffle it will run even better too.
On a Roadstar Adventure.
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Yeah the carpy one comes with a removable metal baffle, not a glass pack. I know they toss a bit of fiberglass, the silencer on my dirtbike is a glass pack. I did not know they were that bad. I feel like it would be a pain on a streetbike anyways, having to repack the silencer every month or something. Thanks man
Date: Sun, 24 Feb 2013 16:32:27 -0800 From: [hidden email]To: [hidden email]Subject: Re: Aftermarket Exhaust & Jetting Considerations
All of the 4 into 1 exhausts have a little bark to them when opened up.
You can get a all metal baffle for them.
Do not get the fiberglass packed style because it blows fiberglass fibers all over the place and you will end up breathing those little pieces of glass.
You can see it it the sunlight when you rev up the bike with that fiberglass packing.
With a baffle it will run even better too.
Working on a CB750 Digger named Rover
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NAML
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Administrator
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FWIW, I have a home made glass pack on my bike made out of a steel baffle wrapped with header wrap. 10K+ miles later and it's still good. Ain't blew out yet...yet.
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Header wrap is different than the glass pack you buy...it's very densely woven, the glass pack is all loose and strandy.
-sean
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NAML
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From what I understand about the carpys exhaust is that it comes in raw form, you wlll have to finish it with high temp paint, or have it chromed. I put a Mac 4-1 that has a black header with a chrome muffler on my 81 and it sounds mean(when it was running, currently chasing an electrical problem lol). As for the jet kit, like tools said every bike is different, you may not need to rejet yours but if you do this is the kit I went with and highly reccomend, for 80 bucks the price is right too. They have excellent customer service as well so if you run into any issues that you just cant figure out you can send your carbs to them at no cost, well shipping costs, and they will do them for you. I have the kit in my bike, and the directions that came with it are very straightforward, and easy to follow. Here is the link, good luck and enjoy the ride. http://www.6sigmajetkit.com/index.html
I know enough to get me in trouble.
1981 Yamaha XS650 Special(current cafe, code name El Diablo Rojo)
1981 CM400C, completed project (code name Home Wrecker)
1981 CB750K, completed project (code name Winter Blues)
SOLD 9-21-2013 gone but certainly not forgotten.
2009 USA Choppers Bad Boy, rigid frame custom chopper.
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Yes it comes raw, I just want to clear cost it with high temp clear so you can see the welds and stuff. I hate electrical, mine was only sparking on 1 and 4 then it would decode it was going to spark in all 4, then go back to two again. Turns out the pickup wiring was bad. Jet kit sounds like a good idea, ill take a look at that. Thanks man!
-sean On 2013-02-27, at 7:52 AM, "barelycompetent [via Honda CB750'S]" < [hidden email]> wrote:
From what I understand about the carpys exhaust is that it comes in raw form, you wlll have to finish it with high temp paint, or have it chromed. I put a Mac 4-1 that has a black header with a chrome muffler on my 81 and it sounds mean(when it was running, currently chasing an electrical problem lol). As for the jet kit, like tools said every bike is different, you may not need to rejet yours but if you do this is the kit I went with and highly reccomend, for 80 bucks the price is right too. They have excellent customer service as well so if you run into any issues that you just cant figure out you can send your carbs to them at no cost, well shipping costs, and they will do them for you. I have the kit in my bike, and the directions that came with it are very straightforward, and easy to follow. Here is the link, good luck and enjoy the ride. http://www.6sigmajetkit.com/index.html
I know enough to get me in trouble.
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NAML
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No problem, I highly recommend that sight for jet kit needs. My electrical issues are completely different lol, I already have a thread started on that, and a few things to try out as well see if I cant get it narrowed down and fixed! Good luck with whatever you decide!
I know enough to get me in trouble.
1981 Yamaha XS650 Special(current cafe, code name El Diablo Rojo)
1981 CM400C, completed project (code name Home Wrecker)
1981 CB750K, completed project (code name Winter Blues)
SOLD 9-21-2013 gone but certainly not forgotten.
2009 USA Choppers Bad Boy, rigid frame custom chopper.
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