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Author Topic: MAC 4 into 1 rejet question  (Read 564 times)

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Offline gmoneymagna

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MAC 4 into 1 rejet question
« on: August 20, 2019, 08:45:27 am »
Hi all! Sorry if this question is beat to death but I couldn't find much regarding CV carbs. My bike is a 1982 cb650sc nighthawk (CV carbs) and I plan to remove the 4 into 4 and replace it with a 4 into 1 exhaust. I may or may not use the baffle. I also have a UNI foam filer in the stock airbox and no adjustments needed so far. Does anyone have a rough idea of how many jet sizes to increase? I am looking at kits like this:

https://www.ebay.com/itm/Jet-Kit-Honda-CB650SC-Nighthawk-1982-Stage-3/331663993843?fits=Year%3A1982%7CModel%3ANighthawk+650%7CSubmodel%3ACB650SC&hash=item4d38b6ebf3:g:WfkAAOSwuTxWBEWW

But I'm wondering if it's better to spend more and get the "pro" kit with a bunch of sizes to be safe.

Thanks!

Edit:

I have also found Randakk's advice:

http://www.randakksblog.com/jetting-advice-for-vintage-honda-cv-carbs/

This post says that I will not need to rejet (although I may need to go back to an OEM paper filter). Thoughts?
« Last Edit: August 20, 2019, 08:51:39 am by gmoneymagna »
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Offline Bankerdanny

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Re: MAC 4 into 1 rejet question
« Reply #1 on: August 20, 2019, 08:51:14 am »
I would think that stage 3 would be a bit much for just a 4-1 and Uni.
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: MAC 4 into 1 rejet question
« Reply #2 on: August 20, 2019, 09:21:31 am »
Try it with the current jetting before you decide you have a problem ahead of time
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Offline Scott S

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Re: MAC 4 into 1 rejet question
« Reply #3 on: August 20, 2019, 09:32:56 am »
 MAC exhaust rarely requires rejetting.
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Offline gmoneymagna

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Re: MAC 4 into 1 rejet question
« Reply #4 on: August 20, 2019, 10:22:01 am »
Thanks guys! I have held off buying a jet kit at this time. I expected a (potentially) unbaffled exhaust to drastically alter the jetting, but it seems that was a misunderstanding on my part. I'll bolt on the exhaust and give it a shot.
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Offline tlbranth

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Re: MAC 4 into 1 rejet question
« Reply #5 on: August 20, 2019, 10:26:11 am »
I have a Mac 4-1 on my '70 CB750. Jets are all original. Needles lowered 1 notch. Runs well, gets close to 50mpg.
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