1982 cb 750F SS wont run right !!

[Tom_Lowe]

Hello i new on here so please let me know if i do anything wrong lol. I have a 82 750F and i cant get it to run correctly. The bike was running great last year for most the year. Then the o-ring on the the fuel distribution tube started leaking.So i replaced it and haven't been able to get it back to normal sense. the carb are 100% clean i guarantee it. iv had them off 50 times. I just installed a carb rebuild kit also thinking that would fix the problem ...it didn't. The bike will start fairly easy and acts/sounds like its running properly. idle is a little rough and it dose stall out at an idle at times. but when i go to ride it it spits and spudders with hardly any power then it will take right off for a few seconds and then its back to spittering and spuddering. the longer i ride it like this the worse it gets. eventualy to where it wont stay nudding no matter what i do. If i pull the choke while riding it improves about 35% and runs significantly better. But with out choke its like theirs not enough fuel. It back fires at times also. i pulled the plugs last night and they were coal black. But sparking wonderfully. IM NOT SURE WHAT TO DO AT THIS POINT. I CAME ACROSS THIS SITE HOPPFULY YOU GUYS CAN HELP ME UT. ANY IDEAS ARE MUCH APPRECIATED!!!

[Beekeeper]

How are the carb insulators and airbox rubbers?  Are the carbs fully seated, all the way into the insulators and the clamps secure?  Proper air filter?  Battery fully charged and charging system functioning properly?  Doesn't sound like too little fuel, sounds like too much air.

[Tom_Lowe]

have new rubber boots going to air box as far as air filter goes i haven't messed with it i think the charging system is gong bad because i have to buy a new battery ever summer beacuse it dosnt put out enough volts to keep it charged

[TOOLS1]

The rubber boots between the carbs, and air box do not have much to do with it running; however the ones between the carbs, and the head have everything to do with it running right. It does sound like it could be a vacuum leak, a fuel delivery problem, or an ignition problem. We really need more information on when, how, and what conditions this happens. The charging problem could be causing this. Does it do it when the battery is fully charged, or just when the battery is low?
TOOLS

[Tom_Lowe]

I also got rid of the vacuum fuel delivery system and I plugged of the vacuum going to the carburetor it's a straight feed of fuel from the gas tank to the carburetorthe bike runs good with a full battery 414 battery gets low and has a hard time however this battery is brand new so it shouldn't have a problemI was told when I took it to the shop that the little box under the seat was not delivering enough power to keep the battery charged however it was close. I haven't replaced the boots in between the carburetors in the engine I'll take a look at them tomorrowas far as having too much air I'm not sure what I could have done to make that happenlike I said I clean the carburetor so many times I could do it however I have not let the car but I have flown out every hole and it seems to be very clean I do believe I put a new magneto  in it also on the bottom left side of cover on engine

[Tom_Lowe]

I have not split the carbs

[seestheday]

If the insulators between the carbs and head were old and brittle they may work until you take the carbs off. After that they'll not seal properly.  

Can you check for a vacuum leak? Spray some flammable fuel there when it's running. If the idle goes up you have a vacuum leak and probably need new insulators.

[Tom_Lowe]

OK I'll try that tommarow. I thought they sealed cause I had to push quite hard to get them to pop in the boots hard enough to punch the bike of the center stand  but I'll try that tommarow! I really appreciate the help!

[LukeM]

Tom, I'm going to move this posting to a more appropriate group.  We usually put how-to stuff in here, such as carb repairs, clutch refurbishing, etc.  Your posting is more looking for help with carbs.

Luke M

[Butcherblock]

Hey Tom-Lowe, welcome to the forum. A trick I learned from jebbysan was to put dielectric grease on the inside of the carb-to-head boot. Makes it easier to slip in, and improves the seal as well. Mine were extremely hard to put on as well, just keep working them in. I pushed them on while sitting on my bike, leveraging my elbows on my knees. How that helps!

[Tom_Lowe]

hey luke , i appreciate you helping me out. like i daid i wasnt sure if this was the spot for this post or not .... anyway i appreciate it as far as the boots go im on my way out to the barn right now. hopefuly  i can find something flammable out ther im wondering if the air cut off valve might have somthing to do with the way its running ?? any ideas . Thanks, Tom

[Half-Caf]

Believe it or not, I had remarkably similar symptoms with my bike at one time. Turns out I had put my jets in the wrong spots  The thing would run ok if you were on the throttle, but would sputter and putt like crazy if you weren't giving it the beans. My build thread has pics if you're interested.

[Tom_Lowe]

Half-calfe believe it or not i read to page 10 of ur build on ur bike last night. sorry u had such a problem with the rotor  but i think my jets are in the correct spot the main jet (102) is in the middle and smaller on on the side. im also wondering if the charging system might have something to do with it but i have a brand new battery so i don't see how that could be the problem right now. what If the head gasket was bad would that do it ? Thanks again ,

[Johnnylevi]

Did you adjust your fuel air mixture screws at all during this process? Might be something to check too. Mine was running really rough and would die once I turned the throttle at all and spat and sputtered until! I synced the carbs and adjusted the air fuel mixture properly. I have an 81SS

[Jack]

I was having the same problem.  I changed my regulator and it fixed the problem. Good luck!!!

[Tom_Lowe]

Johnny, I have taken the carbs  apart so many times it is possible that I messed with them and didn't get them Back in the correct position as far as syncing goes I would have tontake it to someone to do that. What's the regualator do ? Is it electrical?

[Tom_Lowe]

Well I just tryed spraying down the rubber boots with carb cleaner idle didn't change at all. So I hoped on it and took it down the road again. I believe its burning rich I can smell a strong rich gas smell when its at an idle. I pulled the plugs and here what I found    the plugs were coal black again  idk what's going on but its deff not right  it runs OK at certin points  but when ever I try to get on it it just coughs and spits

[Johnnylevi]

You should buy a sync tool. I think they cost about $60, but if you have someone do it i've heard of it costing as much as $500. Its easy to do. I believe they should be 1 and 3/4 turns out for the stock setting. You turn them all the way in carefully making sure not to seat the needle hard. Once you feel it stop stop right then and then start backing it back out by half or quarter turns. Are the plugs oily?

[Tom_Lowe]

I think I had them out 2 1/2 to 3 turns  and no there dry

[seestheday]

Here are the correct jet positions (I had made this video earlier).  I believe you have them correct from your description.



I'd recommend buying a sync tool.  If you get someone else to do it they will likely charge you more than $80 and you'll end up with sync'd carbs.  If you buy the tool and do it yourself you'll likely spend less than $80 and end up with sync'd carbs and a carb syncing tool so you can do it again later if you need to.

Seems like a no brainer to me.

If you don't have a 90 degree screwdriver you also might think about getting one.  It is much easier to dial in the air/fuel mix screws when you have it.