need help ladies

[CBgirl]

I have a 78' CB400 TII. I have taken the carbs off and cleaned them and the bike still is running rich and any throttle given, the bike sputters and it does not fire right. I dont know what else to do. I have replaced the spark plugs as well. Any suggestions ladies?

[indianscout]

When you say "cleaned", did you disassemble them and soak them in carb cleaner and then rebuild them with a kit or did you just rinse them off and put them back on? Honda carbs are very fussy and the tiniest piece of dirt or film will case you major fits. With todays gas being the crap it is, any of it left in the carb for more than 30 days can cause it to leave residue on the needles and only a good cleaning and replacement of some parts will bring it back to the bike it should be. Pin holes in diagrams (if it has them) too small for you to see may be another possibility. I have no reason to doubt your mechanical abilities but I would suggest to send them out and have them professionally cleaned. Then you may even have to have your carbs "tuned" before it'll run good. Hope this at least gives you some direction.


Tim

[Astir]

Carbs can be tricky as IS pointed out. Can you give us more information? What did the old plugs look like?

[indianscout]

Ok, so I crossed paths today with my carburetor guru and hit him up with your problem. He said if your carbs have diaphrams then good chance that is your problem. Now for the bad news......they can run you about $100.00 each! Don't use the aftermarket ones as they will not work and then you will have to buy the ones from Honda anyway. Strip the carbs down and get them cleaned, then clean them again (get the picture?). Have them rebuilt using the Honda carb kit and then take the bike after the carbs are mounted and have them synchronized buy a good Honda mechanic. This is what I had suggested before but was not aware of the after market diaphragms not working. Good luck and let us know how you come out on this.

[CBgirl]

When I say cleaned, I took the carbs off and soaked them in a carb solution. I belive they are constant velocity carbs, so that would mean no diaphrams. I am begining to think it is the jets, but would that cause it to not fire right?

[CBgirl]

O and I replaced all the plugs, and the choke.. the guy who owned the bike before me, had the choke installed wrong and it was fully open while he drove... silly boy

[indianscout]

I would advise to disassemble the carbs completely as soaking the complete carb will not do a good enough job. Yes, a bad or dirty jet will cause failure to fire as there is no gas getting to the cylinder. Sounds like your on the right track CB.

[Condor]

Sounds like you are getting great advice already so the only 2 cents I can add, is maybe the previous owner ran with the choke open because that's the only way they could get it to run.:shrug:

[gypsyangel]

BTW have you checked the lines all the way back into the tank to make sure there's no rust or other bits gumming up the works? Annnnnddd did you gap the spark plugs and make sure they're all firing? And you didn't over oil your air filter and it's clean and ready to go? (just trying to eliminate all the simple items before you have to dig back in)

But yeah, still sounds like gummy jets. Just when you think you're done cleaning carbs....you gotta clean more of the carbs. Anyone who thinks Ethanol won't harm your engine has never cleaned green crust out of their carbs.

[Kitsune]

Those CB400s are freakin awesome little bikes. I want to 2nd what indianscout said on the holes in the diaphragms. In a pinch (and I mean a real pinch) I've seen a mechanic use a couple thin coats of liquid electrical tape to seal the diaphragm holes.

The other thing that comes to mind is maybe the air filters? Are they pods or the stock filters? Dirty pods can be pretty restrictive and really throw your mixture. Even if the stock filters look good and clean, moisture in the air and just time itself can collapse the paper fibers and increase the restrictive qualities of the filter material as well.

Other than that, those old keihin carbs can be a real bear to clean. I had mine (CB350T) run thru an ultrasonic cleaner three times before the carb ran right. I'm still having problems, though...

Hope some of this helps, anyway.

[Luna Tique]

:w2: Kit
It has been a long winter I am glad you stopped in :thumbup:

[indianscout]

Hey Kit,

Holes in the diaphragm will cause it to suck in too much air and screw up the mixture. You may consider changing them out as Honda carbs are extremely touchy. Old age will cause the rubber to shrink and/or crack causing major headaches much like you are dealing with. Warning, Honda carb diaphragms can be very expensive but if it is the difference between having a running bike or a rather large paperweight.....well, you get my drift.... Good luck and hang in there!!!

[CBgirl]

thanks for all the advice!! I soaked the carbs in a carb solution for a week and checked the jets, they all look good. It is still not firing right, anywhere over about 2rpms, it sputters (does not shut off). I checked the air filters and they are good, I am not sure where to go from here.

[indianscout]

thanks for all the advice!! I soaked the carbs in a carb solution for a week and checked the jets, they all look good. It is still not firing right, anywhere over about 2rpms, it sputters (does not shut off). I checked the air filters and they are good, I am not sure where to go from here.


Standard carb cleaner will not work. Remember how I said the old Honda carbs are very touchy? I mean we are talking surgical clean. Buy the strongest stuff you can find and disassemble the entire carb to soak. My local shop uses a marine carb cleaner for about $50.00/gallon (ouch) but the stuff is tremendous and will actually rejuvenate old rubber parts. Just because the jets look clean doesn't mean they are. Get a set of gas welding tip cleaners and run them through the jets or just replace them. It can look clean to the naked eye but in reality it is not. Check for air leaks buy spraying carb cleaner on the manifold and see if the idle changes (make sure you don't get any in the intake wile you are doing this). If there is an air leak it will suck in the flammable liquid and change the idle speed. If you find one, fix it and try it again. I'm sure it is something very simple to fix but as you are finding out, half the battle is to find out what that could be. Keep at it and good luck!

[coffee_brake]

IS is right, it definately sounds like there's still funk in a jet.

It normally does take at least two attempts to clean a carb, sometimes more.
Especially if this is your first time tackling dirty carbs.

It is very good to clean off a table in the garage, get yourself a little egg carton or something to hold teeny, tiny parts, and lots of light.

The pilot circuit can be very problematic, there are washers so small in there that it takes a paper clip with a 1/32" bend in the end to get 'em out. But you can do it with no special tools, and you will succeed if you take your time, get a good diagram of the parts you're cleaning, and keep at it, understanding that you might have to go right back in there.

I've rebuilt a few carbs, and it still took me three times on my latest rescue to finally get the choke passages clear....

[CBgirl]

update:
I have cleaned the carbs once again, checked the starter points, changed the air filter... still no change. I am going to check the stator next or maybe the CDI. Any new ideas? I am going to try and post a video soon.

[indianscout]

You said you changed the plugs right? But did you check them for spark? Pull the plugs and ground out the base of the plug to the engine but do NOT touch the plug as you may get a shock. Turn the engine over an look to see if you have a blue spark...not a puny yellow spark but a large healthy blue spark. If you have a pulse generator going bad this may be the cause but lets hope not as they can be difficult to find good replacements. If you have a good spark, then it has to be something to do with the carburetor or some sort of fuel restriction.

[coffee_brake]

One more thing to look for with carbs: See the 3-4 tiny little holes in the throat of the carbs? The ones that the butterfly moves over when you pull the throttle cable? The buttlerfly should be adjusted so that it exactly covers the first hole halfway. It should cover half of the first hole so that when you look at it, you see it reflected on the butterfly and it's a perfect circle.
AND...on the other side of the carb, spray carb cleaner in holes till you find the one that makes it come out of those tiny little holes in the throat. When you spray carb cleaner and make it come out of those tiny holes, it should come out of all the holes equally in a strong clean spray. Your bike won't run right off of idle if those holes aren't all completely clean. I tell you this because your bike's symptoms do not sound electrical. It sounds like carbs. But yes, at this point I would definately check for spark before going back into the carbs, just to be sure it's not something like a poor connection at the coils (very common). Checking for spark is easy and free, so why not?

I hear you say you cleaned the carbs, but do you mean that you pulled out the pilot screws to include removing the rubber washer and brass washer under each? Did you see carb cleaner coming out of all three-four holes in the throat equally? Did you check the float level? (careful, don't move it until you're sure it's wrong). Did you bench-synch before install? It's more than pulling the jets in the bowl and making them shine. It's not hard, but REALLY cleaning carbs is pretty detailed. Again, not hard or expensive. Just lots of time and lots of painstaking care.

Nobody's throwing stones, but shiny clean brass jets do not mean the carb is clean. Since you don't have someone standing by to show you, we have to tell you this with a whole lotta words. Please ask questions if you don't understand.
The first time you fire up that bike and go for a ride after you clean the carbs yourself, it is SO rewarding...and you'll never let those carbs sit up again!