hi newbie to the forum and cb750 world

[dylansdad022102]

well i bought a 1979 cb750f supersport for $300 can you believe it!! if looks great new tires i had to clean the carbs and polish a bit but its looking great now. well it runs and idles great but i cannot get it to rev past 3500 rpm's. what gives? what can i do to fix it???


please helpfront.jpg

[shabbabear]

what exactly does it do at 3500 rpm ????...sounds like your mains (jets) clogged ....pilot jets work at zero to 1/4 throttle...also did you forget to reclip your needles when you put them back into the carbs...if they're at the bottom then you can twist away but they will never rise...can you still ride and shift as long as you stay under 3500 rpm ???..or have you just tried it in the driveway..we'll try to help..need more info but it seeems like a fuel flow issue...shabbabear

[blackhawkrider]

Is your airbox on?

[dylansdad022102]

hey guys thanks for the quick reply. no the air box wasnt on. i had the carbs on as a trial. just to fire it up. air bax make that kind of difference? i know vaccuum carbs are tricky but i didnt think it would make that kind of difference. and yeah the carb needle is back on right and everything functions smooth. im ordering a new accelator pump this one has a small nick in the side of it.

so i will hook up the air box this time and give it a go

[blackhawkrider]

I did the same thing myself when fixing the last cb 750 I had it wouldn't run past 4000 rpm without the airbox on so I did some research and found out for these bikes it wil not run without it they need the vacuum created by the airbox to lift the slides.

[dylansdad022102]

ok great thats what i was hoping for lol. now the fun task of hooking the air box and the carbs up lol took me 10 mins just to get the airbox in the frame. talk about 10 pounds of shit in a 5 pound bag lol. i will keep you posted

[blackhawkrider]

I hate the airbox, poorly designed. Can hardly get boots on in there. Banged up hands cursing ect. Have fun. It will be fun though to get your bike going Im sure.

[dylansdad022102]

yeah i will try to get it all on saturday night. i have to work tonight.  did you see the photo on my first post? not a bad score for $300

[blackhawkrider]

yeah I did looks like a great deal for $300, thats also how I confirmed it was probably you airbox not being on. Is this your first bike?