This is a link to a previous topic covering the  Gas Tank Venting System
Although the stock tank venting system uses the vent tube in the tank, an aftermarket fuel tank filler cap may have an alternative vent built into the cap itself. You'll have to take a really good look at the cap and see if it vents to atmosphere without using the vent tube in the tank.

On the stock fuel tank cap, when the cap is closed on the tank, the rubber seal is compressed , exposing the vent hole in the cap (see pic)

 

An aftermarket fuel cap may have something similar and it might vent through the key cylinder, maybe, I don't know. Having the stock fuel cap uses the fuel vent pipe to also act as an overflow and spill excess fuel onto the ground and not allow fuel to  flow out the top and all over the tank and seat, or maybe your crotch.

Hi Scotch, "No" still bench testing the carbs and still over fueling. With tube gauges installed a suspended fuel tank. When left for 10 minuets all levels seem to get high, towards the top of the fuel bowls. Then one of them will overflow !!!  almost if the fuel is trying to find the weakest link or the path of least resistance. Then if i move the position of the carbs it will happen on one of the other carbs.  This bike is testing me like no other, even had members of the local bike club round here, checked everything on the carbs. Still don't know what it could be. I have owned 100's of bikes over the years not one had a un-fixable problem. This is going into the realms of the supernatural. Think i will call her Christen    No one can sort out this problem out ! 

Hi Scotch, fitted the new brass floats with the settings as they came from you. When left with the fuel on, and bench tested with the fuel gauge tubes . I can see after about 15 minuets im still getting a overflow ! and all of the tube levels start creeping up. Then one of them seems to be the weakest link and flows from the rear of the carb.  I move the floats about and still having a overflow from different carbs. With no obvious results. ????

 If anyone can shine a light on the following  I would be eternally grateful. A2 model
Going back 3 years, Problem starting the bike. Fitted new plugs, when it did start, very sooty after 40 mile run, and you could feel the bike starting to die . Excessive smell of unburnt fuel.
Bottom air box filling with fuel. Sparks at plugs never looked good !  Voltage only 12.5 V @4000 RPM.

So now this is what I did over the last 3 years, to address these problems-
Float Levels, adjusted using tube gauges to correct levels (not overflowing now)
Pingle tap / petcock fitted 
New stator fitted, now reading over 14 volts @ 4000 rpm
new sets of spark plugs fitted, all of the following tested.
NDW20EPR-U
ND W16 EPR-U (Hot set)
ND W20EP-U (none resistor type)
Main jets standard.

Could this be Coils ? and would I benefit from a set of Dyna s coils but £350 !
Would Pilot air screw have anything to do with this ? or would it be just for that first 1000 rpm ?
Could this be the needle hight ? and would it cause this much of a problem ?
So after all that, Still no improvement. Plugs still sooting up after a 40 mile run !!! The HOT set, ever so slightly better, but still sooting up !
I just Can't give up on this Bike as it's the best Bike i have ever owned, well it would be if I could sort these issues out. I'm the wrong side of 60 now ! so time is running out.
I would like to think I have a few years of riding on this bike,  So any help would be great.
Regards Phil
 

First time posting on here, now that I can being that I finally own a big 6! Ive been upsessed with crazy engineering from back in the day, remember the first time i saw a cbx in person, just in a parking lot at the store, wow i fell in love with giant wide 6 cylinders. Few months back I was ready to move on from my harley road glide with an 88, really loved the bike, but it was just a pig, not much power and on the freeway doing 80 it sounded like it was going to blow revving so high. My dream has always been to have a turbo bagger to go along with my twin turbo show car that im going to start tuning next weekend!!!! (this has been a non running project for 5 years) So naturally already looking for my next build. The hard part was deciding what I wanted to build this turbo bagger on, as I didn't really want to pay the premium for another harley, and turbo v twin doesnt sing to me, then somewhere I made the connection of using a voyager with the base, and the more i thought about it and looked into, I love the idea of an inline 6 turbo bagger, and it already has fuel injection! more critcally throttle bodies that take fuel injectors, which will make building a turbo so much easier. Once I was sold on the idea began the long hunt to find one, and that was hard, there are none out here in utah or really on the west coast. Well one finally popped up within driving distance and it was a screaming deal on top of it! Was a little less then 500 miles from me, so almost a 1000 mile round trip, $750 for one that was in somewhat decent shape, the catch was he had a gl1100 also for $750 and he would only sell them as a pair, weird, but I wasnt going to miss this chance.

Finally made it home, threw a new battery in with some new gas and fuel injector cleaner and she fired right up, changed the oil, sett the tires and its been a blast to ride so far. The front fairing was extremely loose and I found the mounting bolts barely on, actually not sure how they didnt rattle off, got it tightened up, took off the lower side panels as one did have a good scuff on it. Windshield was broken from him storing a DINING ROOM TABLE SET on top of the bike in his garage! like when i got there I spent a good hour just cleaning crap out of his garage to even get to the bike. So I had to trim the windshield way down to clear the broken pieces. He also filled the coolant overflow with oil, i guess he thought thats where oil went? Spent forever flushing that out, the line leading to the radiator looked to be nice and clean and just coolant. He also gutted the stock mufflers, in a very weird way, i should get a picture.

The bike seems to be running pretty good, its not nearly as torquey or quick as I thought it would be, is there any way to tune these dfi systems with different exhaust? How he gutted them it sounds decent, I love hearing it rev, but around 3k rpm the drone is the worst ive heard on a bike
Also do these bikes tend to run hot? Were in a heat bubble in the west right now, its between 90-100F every day, coolant is nice and clean in the radiator and overflow, but the bike tends to always run a little over normal, like if normal is the bars coming to the middle, it usually runs 1 bar past the middle, slow stuff in parking lots and such will give me 2 bars and ive seen 3 bars, where its almost maxed out the coolant gauge, but breifly. The fan is working, after i turn the bike off it continues to cycle on and off.

The top of the motor is pretty ticky also, doesn't sound bad though, is that also normal? Or should i tear down and inspect the valves? also is the cam chain tensioner on these reliable, Ive had to install manual ones on alot of 80's bikes.

For right now Im going to ride the ugly duckling how she is and love her, I wanna do something different with the exhaust, but I just want to enjoy the bike. Im going to start slowly ordering parts to change the look, its probably going to get a harley roadglide front end with harley stretched bags. The turbo project will be something for this coming winter, after my car is all tuned and done.

Also are there any options for handle bars? Wasnt expecting to see these goofy things with how they mount. Also does anyone have this side cover? I dont like how it was bashed in and filled in with whatever, id also love to find a replacement crash bar for the same side. ebay has none and not sure where else to look for those parts.
So excited to finally have one of these!

Hello all, I picked up a 1982 A4 and a 1980 A2 in August. This website is an amazing resource and thanks to all who contribute. I have been reading for hours and hours, can't imagine owning and working on these machines without the shared knowledge of the wizards. I bought Scotch's cleaning tool, just finished a ZX-11 tensioner swap, getting ready to order a new fuel petcock, and evaluating the best way to repair my two coolant overflow tanks. I'm enjoying the experience.

Ty

Hi Kawboy. Sorry but I jumped on to the other debate, as some of the problems looked to be the same. My Needle seats are all Brass ! my Topic was all about Tabs on the floats. Then getting a stable level inside the bowls "not easy and time consuming".
Also in the official workshop manual, lack of a measurement of where to start as a float height. As I've owned lot's of bikes over the last 40 years and never seen a bike without this measurement.
So I started the task to find a fuel level and tab measurment that was stable, without overflowing.

A couple of times in the course of getting my '82 KZ1300 back on the road, I have gotten it running smoothly and up to operating temperature, with all signs of carb fuel overflow gone, only to find on the next fire-up a few days later that the float valves are gushing like Old Faithful again.

When I first cleaned out the carbs I noticed that the float valve needle-and-seats were steel on steel, so there is zero compliance and zero margin for error. I almost burned my first car to the ground because of this kind of stupid design, that would flood whenever the engine was forced to idle in traffic in warm temperatures.

Is this a universal feature of carbed KZ1300s, and if so is there any source of aftermarket float valves that will fit and were not the result of brain-dead design?

Sorry for the editorializing, but they must have known better.

I'm sure it has been previously often discussed but here one more time, the story of my carburetor cleaning and overhaul, because my motorcycle has exhibit symptoms of not properly running which i often see from other members here.
From the beginning I own this bike, it had this typical problems with carburettors, rpm hanging on throttle snap, bogging while driving (first gear just rolling) in to the roundabout for example, super rich on snap wide open under load (overtaking) spark plugs completely black, carbs overflowing or air locks in the fuel line, no problems starting cold thou, but when warm, after standing for 30 minutes or so it was a b**ch to start up again. So here some description and pictures how I resolve those problems to help others tackle theirs. This is how I did,,,,,,, but a lot of tips are coming from Scotch, who is very very experienced in this field, and so first of all I thank you for the help mate.

First obviously disassembly, cleaning, boiling it in distilled water (don't use normal water to boil, it will leave nasty scale stain on and inside of the carb), flushing, blowing with air. I have build cleaning pump, it can move the liquid (fuel, thinner) for and backwards and also I can supply the air in to the system, this because I find that air bubbles help to break off the rust stain or particles in some of more troublesome areas of the carburetor.







And also prior to flushing I soak them for about 20 minutes in Tangit, [(don't spill it, it will burn hole in you lawn, or in the garage floor, also if you take it too long it will start to dissolve the brass gallery pin seal ] to remove some of the stain in the galleries, than I blow the passages with probably enough air to supply the whole planet. After I clean them thoroughly I drunk one bear, and than I started all over again, just in case. You could skip the step with the beer if you want, but I really don't recommend this. For soaking in Tangit, I have removed all the jets, everything else including the butterfly valve and seals, ONLY carburetor body and brass gallery inserts (once I even drill them all out to see what's behind, picture later) remain, any plastic or rubber parts would have dissolve instantly otherwise.

After that as the first step, the assembly of the butterfly valve, with new seals and using loctite 243 thread locker on the screws. Putting the butterfly valves in the shaft slot is difficult at minimum, it requires concentration and steady hand, (if you tired don't do it), return spring must be hanged AFTER you put the screws in both valves. In later stage, while sliding the plates in the slots when about 90 percent of it is in the slot it self, you should move the shaft left and right slowly, repeatedly, with no pressure at all while very very lightly closing throttle in order to set the plates to fit the bore of the venturi (that's the difficult bit) and when they are in, you need to center the holes for the screws (they should already almost fit) almost in the middle for both holes in both valves. Verify the fitment of the plates (by looking through the venturi to the light) before putting screws in and hold the valves closed with the finger on the lever. Next steps: Plastic washer, circlip, and the cap (cap only once, on the left and right carb body) and than so hated leaky needle valve, holding plate, and microscopic size retaining wire clip, emulsion tubes, main jets, idle jets, the plug screw (everything proper clean), float plus pin, finally the float bowl. You done.







Now to the top, first thing I have notice was when applying choke (fast idling cam action), on the left side of the carb link rod was moving down more than the right one, due to play the linkage shaft has developed in relation to the cap. Repair was more or less straight forward, drilling out the bore, making and fitting brass insert using loctite 603 and than reaming the hole to the size and putting all the parts of the pulley together again. Than goes the membrane and slides with needle set to standard spec at first, (circlip in third notch counting from the top or bottom if you have needle with 5 notches, some of the first needles have had only one notch) and finally the cap with four new hex screws, on the left side enricher, membrane with spring, seat and cover. That's one of three carburetor done.







Also while I had them parted I have made new fuel connectors out of brass and with viton o rings (size 7x2 mm). T part is made out of two parts obviously and soldered together using hot air gun.



After i have read the article about carburetor restoration written by Scotch, l build those brass floats, the bodies are coming from bing 32 carburetor if i remember correctly and the arms i made out of brass stripe using the jig.



Also while I had them parted I have made new fuel connectors out of brass and with viton o rings (size 7x2 mm). T part is made out of two parts obviously and soldered together using hot air gun.

After putting all together I set the fuel level to various heights, re-jeted the carb in different combinations to see how it reacts while trying to tackle the wide open throttle rich condition and off idle bog. Also driving with restricted filter or completely open air intake.
All in all it turned out that for me the ideal jetting is main 110 idle 47,5 and the idle screw 2,5-3 turns out it varies between the 6 intakes and is set with color-tune plug and the needle at 4-th notch counting from the bottom. Fuel level sits at 7 mm from the bottom edge but with tendency to 7,5.
I forgot to add, the choke plungers have got now also new viton seal made out of viton sheet.









And also troublesome areas of the carburetor mentioned earlier.





To be able to jet the carburetor or better to say to see what I'm doing I have build lambda sensors in collector boxes under the oil pan, so I can tell what changes is it doing to the engine behavior.

That's it. Unless you'd split the airbox and I could get the top part separate. The bottom part has the coolant overflow reservoir mount broken - I already have one like that...

So, the headlight fork rings, the top airbox, and the fuel tank rubbers (these I need to confirm)

Gavin wrote: Have you checked that the fuel hasn’t drained into the gearbox causing Hydraulic lock, happened on my Z1100 shaft years ago,when laid up for a year, the carbs overflowed fuel went into the airbox then into the gearbox, check oil level if looks over full drop the oil before trying to start it with jump leads, forcing an engine that is locked this way will cost you dear

Gavin makes an excellent point here. Hydraulic cylinder locking has happened frequently. The carbs overflow and fuel runs in to the cylinder(s) and hydraulically locks the cylinder and usually a connecting rod gets bent.

it may not be too late. Before doing anything , pull the spark plugs before attempting to restart. If the the engine turns over and fuel squirts out of any of the cylinders, you have your answer. If it did lock up, you'll have to do some more inspections including a compression test. If a cylinder or more are lower than the rest, you may have bent a con rod.

Have you checked that the fuel hasn’t drained into the gearbox causing Hydraulic lock, happened on my Z1100 shaft years ago,when laid up for a year, the carbs overflowed fuel went into the airbox then into the gearbox, check oil level if looks over full drop the oil before trying to start it with jump leads, forcing an engine that is locked this way will cost you dear

what i am doing is finding out what she is like before working to get her back on the road. ha only done 1000 miles in 10 years and i dont know the history.
starting is a little difficult as everyone else posts. it will start but cylinder 5 and 6 stay cold. reason is little or no fuel. my guess is its gummed up inside.
once runing for a while 5 and 6 cut in and it runs ok. check the bowl and fuel is now getting through.

took it out and it gets hot quite quickly. fan cuts in ok but still climbs into the red.
the water in the lower overflow tank by left foot is cold when engine is hot. not sure if there is an air leak or the pump is not turning?

all things to work on but nice to get anyone elses views.

once running its quite smooth so may not have to get the motor apart, so may not know about the head?

Got all the coils and resistors connected. All the harnesses were done again.

If Neville reads this, just wondering exactly how you changed the profile of the resistors bracket. I am going to see the distance, but with a much less heat generated comparing to the original resistors block, I think even with a bit less clearance there should be no problem.

One thing though - these terminals are exposed. I am thinking about covering them to prevent any possible shorts. Did you address that s well? I am still not decided on how. Anyone a suggestion?

Anyway, except for the fuel level sensor, the bike is all wired for firing





Oh yeah, don't mind the displaced throttle cables. They know their place - just waiting for the carburetor. Next thing carburetor bench fun.
And the clutch cable will either stay there with a couple ties, or will be moved outside. I actually have seen done it both ways.
ANd another one - my third edit, haha. The radiator overflow hose will be put in place as well when putting all together.

Hi Tim,

After finishing off the bike at the weekend the final job was to balance carbs and the usual tweaks. Well, the carbs refused to balance with all kinds of popping and back firing and the middle carburettor refusing to stop overflowing fuel into the air box. The carbs were on and off 3 or 4 times on Saturday with me finally noticing that the left carburettor throttle slide was sticking and not returning to the bottom position.

Cleaned throttle slides and bores, reassembled and bench set carbs by using Scotch’s paper strip method. Started bike up and couldn’t believe how close they are. Only the left carb was about 3 hg different to the other two carbs. Adjusted the left carb and the bike was very responsive and seemed to run perfectly. Tightened everything up and restarted bike. Ran ok for a few minutes and then a misfire occurred. Noticed cylinder number 5 was not running as hot as the other cylinders. Checked the plugs and it’s oviously running rich. Cleaned plugs and restarted and once again gran perfectly. Think I’ll order a colortune to carry out the final adjustments.

A friend called round today to have a look at the bike and obviously wanted to hear it running. It refused to start, choke on or off, it didn’t even cough. Will try to have another look later on this week as have it booked in for an MOT on Saturday.

Regards

Martin.