cb750 not reving past 6000

i recently got a 81 cb750 and i took the carbs off and cleaned them cause the bike would barely run. now the bike runs decent but it doesnt seem to want to go past 6000rpm. the tank is pretty bad inside so i put some clear line and a fuel filter in place to make sure i didnt get anymore rust in the carbs. i will get the tank redone or something once i get the bike running right. it has a kirker header on the bike with no packing in it with a stock airbox. could it be that i just didnt clean the carbs good enough or might it be something else? i didnt bother the mixture screws when i cleaned the carbs. could that have something to do with it? i just didnt want to have to re sync them up. i have cleaned carbs before this way and had good luck but maybe these were to bad to do that way? am i not getting enough gas maybe? also today i noticed that #2 cylinder was not firing cause the pipe was not hot after i started it. i think that is why it wont rev right but any suggestions would help thanks. by the way it has spark on #2 just not getting gas i guess.

 

Gotta get that tank clean
Itll clog that filter fast!
Are you driving it when it wont rev about 6k?
If driving? Clutch plates
Or stationary?
Carbs
Do the 81 750s have hydraulic lifters like the newer ones?
Shoot up a pic of it if you dont mind
Mixture screws affect until about 3-5k rpms. Always SHOULD clean them. Washers and O rings are cheap. I might have a few extra.
Check the drain screw on cyl 2 and see if the bowl is getting gas
If not, clean the valve seat again
Did you install a new carb kit or just go for a quickie clean?
Quickie cleans work 25% of the time..... But mostly not...

-Chris

 

You really are an optimist. I give it more like 2.5% of the time. Especially if the bike sat with gas in it for any length of time.

Shooter.
As you did not do a complete tear down. I am going to take a shot in the dark, and say that the jet holder/emulsion tubes are still clogged.

Syncing the carbs is a routine maintenace item. As the engine runs it changes ever so slightly due to wear, carbon buildup etc... This over time will change how good the sync is on the carbs. Sooner or later the carbs will need to be resynced to balance the cylinders out again.

The valves are the bucket/shim style just like the XJs. These will need regular checking, and adjusting also.

The only thing you are going to get from taking short cuts is a foul running bike that you will never be happy with.

Ghost

 

well when driving up the road is when it wont rev past 6, actually it will but not easily. i know taking short cuts isnt the best way but at the moment im really tight on money. also i dont have a set of gauges to sync the carbs so that is the biggest reason i dont want to tear them apart. the PO said the carbs were rebuilt 2 years ago but they really were NOT. he said a lot of stuff that wasnt true. the clutch is good in the bike its def not it slipping. i checked the drain screw and it had gas coming out of it, so it is getting gas, how much though im not sure? i also dont have tags on the bike so its hard to give it a proper test ride. so far i havent seen any rust in the filter or the clear line. was wanting to make sure the bike was gonna run right before getting the tank done. also the PO says he had it done 2 years ago but once again must have been a total half ass job cause its coming off everywhere. i think imma tear the carbs back off and reclean them and try to borrow a set of gauges or have a guy i know do it for me. it also could use a valve pan gasket on it so i will prolly check valves at that time. also i did clean the tubes out pretty good that the jets go in. im thinking from the way everything on the bike looks like all the carb screws stripped out and how everything was done completely half ass that they were never right when he had the bike. so i guess another clean and a tune will prolly do it.