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  1. #1
    CB750 Member Nighthawkbobber1990's Avatar
    Join Date
    Sep 2019
    New bern , NC

    92 nighthaw 750 fully hollow muffler re-jet needle washer mod help!!!

    Building a 92 nighthawk bobber bike was given to me so im doing this as cheap as possible . I completely hollowed out both mufflers up to the baffle and bike runs quite choppy of course i know there a many threads about this but ive yet to find someone who fully removed all three um baffle walls if you will i cleaned carbs have not installed a rebuild yet that i will soon have to buy of course ... Do i have to re jet if so what size (stock is 112) so maybe a 125,127,130 etc etc... or if i can put a washer under the carb needle to move up for more fuel flow running stock air box my gf helped with posting this and wants to ride it i could put the bike back to stock (which would be kind of boring) buying a new exhaust is too expensive no disrespect but i just dont have the money right now i cut the seat (going to put a shovel head seat on) i have a trailer fender spray painted rims and and lower fork legs got $55 dollar ape hangers when this problem is solved and a couple other things i will post pictures and Pics, parts and prices of the whole build its a cheap build that i want to show people is possible to do on a budget and WITH YOUR HELP OF COURSE ...please!

  2. #2
    CB750 Guru amc49's Avatar
    Join Date
    Sep 2015
    Fort Worth TX.
    Don't be surprised if you have to jet DOWN not up, that exhaust was tuned better with all of it in place. Honda was not lying when they said modding the OEM mufflers would make it run WORSE. BTDT on a DOHC F bike, and on others. It screams to you that you lowered the power in a big way. If the OEM CV type carbs are being used it will go too rich as the exhaust is flowing worse and it happens when the slides quit lifting as much due to engine power being down. CVs run far better a little bit lean and why people who assume the carbs must jet up run into so many problems. The airbox is only the start of that.

    There is absolutely no one that can literally begin to tell you what jet to go to there, you will be the test guinea pig there.

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