Topic: Carb question ohhh.

[Mavryk03]

So finally got my all wiring figured out and got the lights working from some good guys on this forum  . Got the seat on and put a splash of gas in the tank and started the bike up it took a couple of times to start just had to get the gas in the carbs, and finally started let it run for a couple of min and shut it off and went inside to change. Came back out started up fine got on and took a ride to go to the gas station to put some more gas in the tank, and  about a mile done the road when I would give it more throttle it would bogged down so I thought it was just b/c I need some gas, got to the gas station and put some more gas in the tank and took off again about 5 min later it started to bogged again so I pulled off and was checking everything, And gas was pouring out the bottom of the float bowls so I tapped the carbs b/c I figured the floats were sticking and it stopped pouring out and I just drove how and I ran fine again and was almost home and it started to bogged again but made it home. So is there anything to I do like put a bottle of fuel injector cleaner in I have already take the damn carbs apart for the 4th time don’t feel like it again. Thanks for the help. Matt 

[ANVkevin]

Was there gas pouring out a second time? If so, are you running in inline filter? My guess would be if your bike hasn't been ran in awhile crustys from the gas tank are making their way to your carbs.

I would pour some gas from the petcock into a clear bottle to see if it is debris from the tank.

[flybox1]

seafoam is good  just follow the directions on the can.
refresh our memory of your bike setup....
at what rpm was it bogging? air filter or pods?
timing and advance checked? what did your plugs look like after the ride?
even tho you un-stuck you floats, what height did you set them at?
did you bench sync AND vac synch your carbs? change your pilot or main jets?
what exhaust?
details, Mav....details  

[Mavryk03]

Was there gas pouring out a second time? If so, are you running in inline filter? My guess would be if your bike hasn't been ran in awhile crustys from the gas tank are making their way to your carbs.

I would pour some gas from the petcock into a clear bottle to see if it is debris from the tank.

i had it running a couple of weeks ago i have just been working on the wiring, and inline filter is the filter in the gas tank if so i have a brand new one in it.

[Duanob]

My guess is crap from your tank made it's way into the float needle jet. Sucks but it happens frequently. Does your bike run good at first then bad after a few minutes of running? Could be a misadjusted float not letting enough gas into the bowl.

[ANVkevin]

This is what I meant by inline filter.

                                  definitely NTS



It's one of those great debates here on the forum. I use one as well as the filter inside the tank. I hate pulling carbs and if it saves me having to do it one time, having one was worth it.

Maybe someone else will have a better idea of whats going on. As far as I can tell, more than one float being stuck makes me think gas particles. Having one faulty float is probable, more than one...not as much.

[flybox1]

Could be a misadjusted float not letting enough gas into the bowl.

yes, that,  or too much gas 
first check batt is good. that there are no air leaks from the boots. af screws are set proper, timing and advance set right, clean your plugs.
if your tank is clean, there is no need to have an inline filter.
drain the bowls one at a time to see how clean the gas is....
if your gas is clean, and the overflow has stopped, then i suspect uneven carbs settings.  if you are POSITIVE internals are clean and set right, do a vac sync.
 

[Mavryk03]

seafoam is good  just follow the directions on the can.
refresh our memory of your bike setup....
at what rpm was it bogging? air filter or pods?
timing and advance checked? what did your plugs look like after the ride?
even tho you un-stuck you floats, what height did you set them at?
did you bench sync AND vac synch your carbs? change your pilot or main jets?
what exhaust?
details, Mav....details  

sorry i know details details... seafoam that was the stuff i was trying to remeber, anyway it was bogging around 4000 4500 rmp in 3rd and 4th, it has pods but im trying to get all the stuff for my airbox so i can put that back on there almost ahve eveything so stuff should be here today, timing is good didnt pull the plugs, floats are at 22mm if you mean by bench sync i got a carb syncornizer and sync them up got it running smoother i have not changed the pilot or the main jet and the exhaust is 4 into 1 and the my bike is a 550k1 75 hope that helps thanks buddy

[Mavryk03]

This is what I meant by inline filter.

                                  definitely NTS



It's one of those great debates here on the forum. I use one as well as the filter inside the tank. I hate pulling carbs and if it saves me having to do it one time, having one was worth it.

Maybe someone else will have a better idea of whats going on. As far as I can tell, more than one float being stuck makes me think gas particles. Having one faulty float is probable, more than one...not as much.

yeah i tryed to put one on those on but i just didnt have ebought room

[flybox1]

i suspect most of the bogging will dissapear after you get back to a stock airbox/filter.
if your main jets were up'd for the pods, be sure to bring them back to stock to match your intake.

[Duanob]

i suspect most of the bogging will dissapear after you get back to a stock airbox/filter.
if your main jets were up'd for the pods, be sure to bring them back to stock to match your intake.

That's my feeling as well. I cringe anytime someone has carb troubles followed by "I have pods and aftermarket exhaust" because that is probably the reasons for the bad running bike. Don't knock yourself out by re-doing your carbs until you get your airbox straightened out. Check your plugs that will tell you a lot, like running lean because of the pods.

[Mavryk03]

i suspect most of the bogging will dissapear after you get back to a stock airbox/filter.
if your main jets were up'd for the pods, be sure to bring them back to stock to match your intake.

yeah the po had the pods so i just kept them on there after talking to everyone i come to the concolsion they are just for show so yeah i will be putting the stock box back on and hopefully he didn't change the main jet he didn't seem like he knew alot but i could be wrong.

[Mavryk03]

Thanks again for all of your help guys your best  and i will keep you up dated about it if i have some more probs just wanted to get a couple rides in before it gets to cold i had planned this winter rebuild everything so i may jsut get started early  thanks again guys

[Gaither]

All good advice.

However, whatever else he does, first he's gotta get the carbs to stop flooding the bowls and running over.

As for in-line filters, isn't it all just a matter of opinion and choice?

I put one in when we did the carbs last summer just for added protection.

Very likely, if Mavry had put on in when he went through his carbs, he wouldn't now be flooding the float bowls [?]! IMHO, a clogged in-line filter is FAR better than messing with the carbs again.

Yeah, he likely will have to clean the tank and in-tank filter - which as I recall, he said was new.

[TwoTired]

As for in-line filters, isn't it all just a matter of opinion and choice?

I put one in when we did the carbs last summer just for added protection.

Only one extra?  Gee, if you really want protection you should add three or four more of those in line filters.
Can't have too much protection or fuel to clean!   

Filter 101-

Filters block all particle sizes larger than their membrane or mesh weave allows to pass.
The stock filter (in good condition) won't allow any particle size to pass that can block the smallest passage in the carbs, usually the slow jet, (or IMS if equipped).  This means the carbs can't get stuffed if the stock filter is in good functioning order.
A second inline filter, (or third or forth, etc.) will only capture particles that:
A) would normally flow right on through the carbs/engine.  Or,
B) traps finer, (inconsequential) particles until the filter becomes restrictive and/or blocks fuel flow.  This adds a routine replacement interval to the scheduled maintenance of the machine, (which most operators don't do until there is a some sort of breakdown).

However, most immediate problems with inline filters on the SOHC4, is corrupted routing of the gravity feed fuel system from tank to carbs, as fuel doesn't often travel against gravity. (and flow gets progressively worse as the inline filters get more restrictive while trapping those finer particles.  This issue exacerbates as the tank fuel level gets lower and the head pressure reduces.)

Of course, if the selected inline filter(s) passes particle sizes larger than what the stock filter does, it will never clog up, cause the stock one is doing all the work.  But, it is also a pretty useless add on if it actually performs no active filtering function and messes with the smooth gravity feed transition from tank to carbs.

Cheers,

[Gaither]

Two-tired

All points appreciated and very well taken.

I'm not very smart but I'm smart enough not to argue with you, whom I consider to be an expert on these ol' bikes. You have already helped me overcome my ignorance in solving my elec problems. So, I consider what you have said to be the facts on the matter.

FWIW, Only one in-line, since it is a single outlet petcock. The line and filter are carefully positioned so as to not effect the gravity fuel flow. So, there's no "down-side".

I readily admit the in-line filter is absolutely redundant particularly considering the OEM in-tank filter design. However, since I admit to being paranoid about these ol' carbs (that have been cleaned, etc. and synced), it makes me "feel better" knowing it's there "just in case".

Having said all that, I still agree with what you said, Two-Tired.

Thanks

 

[RainCityRider]

Funny, after 6 years a rebuild (I didn't rebuild the carbs) and lots of miles my 78 CB750 started doing the same thing last night. Didn't take the time to play with it at the time, I just shut the fuel off at the petcock. But I went out to check it a few min ago and one of the float bowls is leaking like a sive as soon an I turn on the petcock gas starts running out of the overflow tube. I do have an inline filter and the clearance was an issue. They make them with a 90 degree bend seemed to work for me. Now to try to figure out this problem.

[flybox1]

Funny, after 6 years a rebuild (I didn't rebuild the carbs) and lots of miles my 78 CB750 started doing the same thing last night. Didn't take the time to play with it at the time, I just shut the fuel off at the petcock. But I went out to check it a few min ago and one of the float bowls is leaking like a sive as soon an I turn on the petcock gas starts running out of the overflow tube.

might be just a stick flot from being turned off. bang on the bank of carbs with a chunk of wood or rubber mallet while slowly turning on your fuel.

if that doesnt free it up, time to clean the crabs out of your carbs.

[RainCityRider]

I was afraid of that. It looks like it is only #2 that is leaking.

[RainCityRider]

So I gave it a little love with a piece of wood and a hammer. seems to have worked.......for now. Any good resources for rebuilding the carbs? ie. videos or step by step directions. I'm a bit of a gumbi and have never done it before but it could make a good winter project. I'm mechanically inclined, with a little help from a buddy and pointers from my shop I rebuild the engine and replaced the rings and seals, had the shop rebuild the top end and lap the valves.

Apparently this bike has a set of carbs that don't have replaceable jets. A buddy said he had drilled them out before but that sounds complicated and potentially catastrophic. And #2 isn't adjustable it is the baseline and you set the others as close as possible-ish.

Sats: 1978 CB750
Blown out 4-4 exhaust
KEI * HIN Carbs with air pods
spark plugs are black, which is weird because after I rebuilt the engine I replaced the plugs after 500 miles and they were white.....?

not sure if the carbs have been re jetted, I assume not, but I have never done it and not sure I want to start taking power tools to my bike.

[Duanob]

Mavryk03 I know this is off topic but have you pulled your intakes and check the gasket/O-ring? They get brittle and crack from heat. They are cheap and easy to replace and well worth it.

As far as filters go, I have the same bike as mavryk and I didn't have room either. I noticed the gas line crimped when the tank was in place. Easy to miss that if you don't recheck the lione once the tank is installed. Could definitely cause fuel starvation. So no inline filters for me either.

Did you get your leak problem sorted out?

[Mavryk03]

Mavryk03 I know this is off topic but have you pulled your intakes and check the gasket/O-ring? They get brittle and crack from heat. They are cheap and easy to replace and well worth it.

As far as filters go, I have the same bike as mavryk and I didn't have room either. I noticed the gas line crimped when the tank was in place. Easy to miss that if you don't recheck the lione once the tank is installed. Could definitely cause fuel starvation. So no inline filters for me either.

Did you get your leak problem sorted out?

no i didnt think of the intake o-rings i will have to check them i put new ones on last year when the motor was rebuilt but you never know. I bought some seafoam so im going to dump that in the tank and see if that helps with the sticking floats i heard good things about this stuff so i was going to give it a try today and ride it around and see what happens cross your fingers and you have the same bike there is no room to put an inline filter i tryed ike i said and there is no good way to put it so gravity takes over lol

[bollingball]

(RainCityRider) You may want to start your own thread.It will be easier to find you for help. Do you have a 750K or 750F model? They have defferant carbs PD42a or PD42b.

[Duanob]

"no i didnt think of the intake o-rings i will have to check them i put new ones on last year when the motor was rebuilt "

You're fine then. Mine were 34 years old. All my rubber was/is dreid and cracked. Slowly replacing all when I get the chance. it's amazing how it effects the way things run.

I wouldn't bet the seafoam will help a sticky float. it may clean out the float valve seat. You can pull your bowl plugs and use something long and skinny to poke around at the float. If it is a stuck float you will know it.

[Anti-Johnny]

I am having a similar problem. My number 2 is leaking. I have banged on it to no avail. I ordered a gasket, hoping that was all it was. But I had it over at the mechanics for a bit and he assures me it is an O Ring. I have been looking for a good video but all I can find for these carbs is how to clean them. Just read through my clymer's chapter on Carbs and it doesnt show specifically how to access the O Ring at the T. I was hoping for a simple fix, but it is looking like the whole carb may have to come apart to access that O Ring. Unless one of you fine folks can help us out.