Topic: 1976cb750k help!

[MOD27]

  So the bike seems to be running just ok.  Runs awesome on the high end and crappy on the low.  I recently put a 4 into 1 vance and hines exhaust no baffle.  Stock air box. re-jetted 105 to 110 in the mains. Needle clip is in 2nd position from the bottom that's the way it was when i got the bike I'm not really sure what that should be set at so i left it alone. air and fuel mixture screw seems to run the best at about 3/4 out. Any help would be greatly appreciated!  I work on the bike more then ride getting fed up.

thanks,
mike

[john thompson]

Hi,

   you can try to change the stock air box to the cone shape filters. Alot of bikes can be funny about to much air leaving the bike and not enough getting in. Had a Yamaha Maxim put straight pipes ran like crap but sounded great. Bought some cone air filters and took out stock box and man it woke up.

just a suggestion


John 76 cb750k Philippines

[xsmooth69x]

  So the bike seems to be running just ok.  Runs awesome on the high end and crappy on the low.  I recently put a 4 into 1 vance and hines exhaust no baffle.  Stock air box. re-jetted 105 to 110 in the mains. Needle clip is in 2nd position from the bottom that's the way it was when i got the bike I'm not really sure what that should be set at so i left it alone. air and fuel mixture screw seems to run the best at about 3/4 out. Any help would be greatly appreciated!  I work on the bike more then ride getting fed up.

thanks,
mike

put everything back to how it was when it was working fine thennnnnnnnnnnnn

put the new exhaust on and see how it runs

if its fine then leave it.

if not then move the needle clip see how it runs then

still runs like crap well then re post on the forums lol.

i just think there are too many variables if you slapped the new exhaust on then changed the needle position and re jetted the bike

[Retro Rocket]

Hi,

   you can try to change the stock air box to the cone shape filters. Alot of bikes can be funny about to much air leaving the bike and not enough getting in. Had a Yamaha Maxim put straight pipes ran like crap but sounded great. Bought some cone air filters and took out stock box and man it woke up.

just a suggestion


John 76 cb750k Philippines

Bad advice for a bike designed to use velocity stacks and an airbox.

Most 4 into 1 pipes flow more and need a change of jets....

[MOD27]

Thanks for the posts!  I did rejet to i went from 105's to 110's on the mains and im gonna try putting the needle clip to the middle position because it seems to be running lean right now.  I have a set of k&n pod filters but im done with trying to figure that #$%* out so i went back to the stock air box.  Recently found gas in my air box so im replacing a bent float and waiting for carb kits to arrive.  Hopefully this solves some issues haha but who knows.

thanks,
mike

[Markcb750]

Are you sure you have the low speed orifice and control vent of each carb well cleaned out? 

I would not take off the stock airbox and inlet venturies.

Have you balanced the carbs as part of the modification to the new exhaust?  Por balance can lead to bogging, idling problems, and excessive vibration at all speeds.

[MOD27]

Yeah i blew air through everything....One issue i found recently is gas in the air box due to a bent float so im getting a new one of those and i have carb rebuild kits coming because im pretty sure some of the needles are sticking too and ive cleaned the carbs twice.  The bike will run well for alittle while then go to crap.  so once i get all that stuff put in im gonna carb sync it again witch should be around a 8 on the guage?

[Markcb750]

My K6 also had trouble with floats, even after setting them to the manual.  eventually I dialed them in.   Overflowing into the airbox was a symptom I kept having till I got a better set up. Eventually I put on a set of cabs I salvaged from a 75F0 that had not been altered from factory settings. 

With the Carb balance there is no magic number such as 8 on the gauge. I could not get mine to achieve the setting from the manual, a common result on these old machines. Getting them all to indicate the same and settle each time equally at about 1100 rpm was the key to mine running well.  I used the floating cylinder based  Carbtune unit I borrowed from Nikkisixx.

Adjusting the slow mixture screw is interesting because it takes about 30 seconds for a change in or out to take effect.