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Author Topic: Jetting for my exhaust cb500  (Read 1042 times)

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Offline tennesseebreeze

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Jetting for my exhaust cb500
« on: November 14, 2014, 06:45:34 AM »
I could use some advise on jetting my carbs correctly. I have a 73 cb500k2 with a newly rebuilt engine, standard bore and new rings, re-cut valves and valve seats. I've also got a stock airbox. I have a 4 into 1 MAC exhaust system on it's way and I want to know what kind of modifications to the jetting, needle position, or anything else I need to do to it to make it run right. I believe I have #110 and #80 jets in my carbs now. Any advise or links? ???
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Offline CBGhia

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Re: Jetting for my exhaust cb500
« Reply #1 on: November 14, 2014, 06:49:08 AM »
Usually, you do not have to rejet for an exhaust change.  At least, not for switching to a Mac.  Maybe if you ran it without the baffle, but it should be fine with the stock airbox.
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Quote from: dave500 on February 14, 2014, 03:53:33 AM
if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
"The cleaner the dipstick, the closer to God." -Rev. Horton Heat
“Faster, Faster, until the thrill of speed overcomes the fear of death.”  - Hunter S. Thompson

Offline Deltarider

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Re: Jetting for my exhaust cb500
« Reply #2 on: November 14, 2014, 07:00:35 AM »
Quote
Usually, you do not have to rejet for an exhaust change.
+1
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Offline tennesseebreeze

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Re: Jetting for my exhaust cb500
« Reply #3 on: November 14, 2014, 07:09:39 AM »
Quote from: CBGhia on November 14, 2014, 06:49:08 AM
Usually, you do not have to rejet for an exhaust change.  At least, not for switching to a Mac.  Maybe if you ran it without the baffle, but it should be fine with the stock airbox.

Really? Even from a 4 into 4 to a 4 into 1? That's good news. I must have a lot of ill-informed friends. I guess it would be different if I went to velocity stacks or pods?
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Offline CBGhia

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Re: Jetting for my exhaust cb500
« Reply #4 on: November 14, 2014, 07:44:53 AM »
Quote from: tennesseebreeze on November 14, 2014, 07:09:39 AM
Quote from: CBGhia on November 14, 2014, 06:49:08 AM
Usually, you do not have to rejet for an exhaust change.  At least, not for switching to a Mac.  Maybe if you ran it without the baffle, but it should be fine with the stock airbox.

Really? Even from a 4 into 4 to a 4 into 1? That's good news. I must have a lot of ill-informed friends. I guess it would be different if I went to velocity stacks or pods?

If you went to Pods or stacks, there would be a lot of rejetting, and then more rejetting to dial it in, then more rejetting, and maybe a little more rejetting. 
The stock box is where it's at!  All the cool kids are keeping them.   ;D
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Quote from: dave500 on February 14, 2014, 03:53:33 AM
if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
"The cleaner the dipstick, the closer to God." -Rev. Horton Heat
“Faster, Faster, until the thrill of speed overcomes the fear of death.”  - Hunter S. Thompson

Offline flybox1

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Re: Jetting for my exhaust cb500
« Reply #5 on: November 14, 2014, 08:02:47 AM »
Quote from: tennesseebreeze on November 14, 2014, 06:45:34 AM
I believe I have #110 and #80 jets in my carbs now. Any advise or links? ???
:o  please confirm this ^
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

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Offline tennesseebreeze

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Re: Jetting for my exhaust cb500
« Reply #6 on: November 14, 2014, 08:22:26 AM »
Quote from: flybox1 on November 14, 2014, 08:02:47 AM
Quote from: tennesseebreeze on November 14, 2014, 06:45:34 AM
I believe I have #110 and #80 jets in my carbs now. Any advise or links? ???
:o  please confirm this ^

I'm pretty sure the originals were #100, but when I rebuilt the carbs, the kit they sent had 110's, as far as I remember. But I will confirm that when I get back in the shop.
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'79 CB750F, '73 CB500K2, '78 CB400A, '71 CL100

Offline flybox1

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Re: Jetting for my exhaust cb500
« Reply #7 on: November 14, 2014, 08:30:24 AM »
your #80 pilot jet size is more of a concern. 
its 2x (or more) as big as it should be.
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mine…"

Offline tennesseebreeze

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Re: Jetting for my exhaust cb500
« Reply #8 on: November 14, 2014, 08:41:24 AM »
Quote from: flybox1 on November 14, 2014, 08:30:24 AM
your #80 pilot jet size is more of a concern. 
its 2x (or more) as big as it should be.

Ahhh. I may be totally off with that number. I'll check it out. Thanks.
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'79 CB750F, '73 CB500K2, '78 CB400A, '71 CL100

Offline CBGhia

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Re: Jetting for my exhaust cb500
« Reply #9 on: November 14, 2014, 10:16:39 AM »
Quote from: tennesseebreeze on November 14, 2014, 08:22:26 AM
Quote from: flybox1 on November 14, 2014, 08:02:47 AM
Quote from: tennesseebreeze on November 14, 2014, 06:45:34 AM
I believe I have #110 and #80 jets in my carbs now. Any advise or links? ???
:o  please confirm this ^

I'm pretty sure the originals were #100, but when I rebuilt the carbs, the kit they sent had 110's, as far as I remember. But I will confirm that when I get back in the shop.


Those 110s will be way too much unless you are running pods.  The stock 100 main should be good.  The pilot jet should be a 40 iirc. 
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CB550 Cafe, GL1000, Buell Ulysses
Quote from: dave500 on February 14, 2014, 03:53:33 AM
if you dont trial spin the camshaft in the head and cover you are a novice,with no natural mechanical appitude,destined for destruction.
"The cleaner the dipstick, the closer to God." -Rev. Horton Heat
“Faster, Faster, until the thrill of speed overcomes the fear of death.”  - Hunter S. Thompson

Offline tennesseebreeze

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Re: Jetting for my exhaust cb500
« Reply #10 on: November 18, 2014, 08:53:02 AM »
Well, looks I was confused because the kits I bout had a few different sizes. I have 100's and 40's. I'm sticking with the stock airbox and the pipes just arrived yesterday. If all goes well, I think it should be able to be tuned as is. Thanks guys.
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'79 CB750F, '73 CB500K2, '78 CB400A, '71 CL100
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