83' GSX 400 F - no idle, dies. Need some advice

[Guest]

Hello again ladies and gentlemen,

Today I am writing to you because I need some advice/help. Here's the story:

In the winter season I hired 3 diffrent people in overall to take care of carbys of this little psychopath which were really nasty inside, a lot w particles and sludge in float chamber for example. I bought new set of jets, needle valves, choke valves. Slider and diaphragms were fine still so I left them be. First guy rebuilded carbys and adjusted them to the point where she was eating 12L per 100km. I couldn't ride more than 150-180km on one tank, radiculous. I took it to the other guy next, he adjusted it so the mileage was quite ok, but idle was funny, but it was there. And third guy made the idle completely gone. I asked every 3 of them about air filter and I found myself that somebody before I bought her has wrapped Vacuum cleaner HEPA filter around the cage and secured it with zip ties... Jesus christ... I ordered MEIWA filter from Japan and installed it previously soaking it in Bel Ray air filter oil like the book says it should be moistured in oil. With vacuum cleaner filter and MEIWA now she just won't hold idle, it is GONE. You can set 1100/1500/1800 - she dies anyway regardless. I can only set it like 2000 rpm on idle, but that hurts gearbox when 1st gear is shifted. When I stop with that dying idle - what I mean by that - you run straight into red light on crossroad slowly braking, engaging neutral - she still goes like 2000 rpm idle for few seconds and then she starts dying. I have sprayed whole intake with deodorant - no result, no reaction to that. Throttle cable is new, isn't locked on tight, has some clearance it was lubricated in winter, runs very smooth - it's not that. So, nobody in my city can fix this, then I need to fix it myself.

I wondered how and I thought of colortune. In my country it is really expensive, one plug costs 300 so I am not able to buy a set of 4. This raises another quesiton then. How do I tune whole 4 carbs with one colortune only? I am worried about threading back normal spark plug in hot engine. What I should do then? Warm up engine, adjust one carb after the other in meantime just waiting for the engine to cool down to screw in normal spark plug? I just don't want to destroy cylinder head. I guess that colortune is my only hope now...

Above is a clip showing the problem. I have a lot of experience in two stroke engines and I can just hear that something is wrong with mixture but I am not that good with four strokes like my Katana so I really don't know what hurts her... Valve clearance was adjusted like 2500 km ago so I doubt it making any diffrence.

If somebody can share something, thank you I have no other option to ask for any help, local repairman seems to just fail the job and take a lot of money for it.

[Gorminrider]

Himer, Keep looking for a good mechanic..
Judging from your video, your bike does not seem "worn out"!.... a worn out four-stroke bike will have other symptoms-clouds of oil from exhaust, knocking and rattling deep in the engine etc.
If you want to do your own work, you will find a lot of help in the older posts and it will help to gain knowledge that will help you choose a mechanic when you need one.
Fortunately, your English is excellent! start here BikeCliff's Website
In this case, it seems you should pay particular attention to "idle mix" screws. You will find several threads and info on this particularly for 4 cylinder motors. Try out the search function. I don't think you need to buy "colortune" plugs... You should start with the Shop Manual. If you can't find one use one from a similar bike with four cylinders and similar carbs..and sometimes other bikes' manuals have tips or better explanations that apply to your own bike.

BUT You can only do any this from a good baseline because everything else must be "known to be good" and set to the manual's baseline before you can get to tweaking by taking other advice or "tuning" the bike by adjusting idle mix or any other adjustment.

One important "tip" about idle mix is that they must make a perceived difference as you turn them in and out. A four cylinder bike will be harder to "perceive" but using gross methods will get you started. Warm up the bike. Best to Get a fan or several on the engine to duplicate motion that keeps the bike cool. Make notes. Note the number of turns they are "out" presently. Then turn them to the manual's setting. Any difference? Turn out all screws two more turns. Notice a difference? keep experimenting one by one or two by two . You will find that just being able to access all those idlemix screws will be a lesson in mechanics! Taking the tank off and securing it sideways across bike will help.

If not, this means: the passages are not clear, the idle jet is still dirty, the idle mix screw is broken etc., etc. You DID say the carbs were very dirty when you got the bike and It's very possible that they are not as clean as you think they are .

Again, this means YOU have to do it.

[Himer]

In my city there are no more mechanics to look for, maybe in other cities but I would need to transport the bike somehow and then get it back and it will be quite not possible - I work. The reason I am sometimes so worried to touch her is because this model is extremely rare in my country and you can count on fingers how many bikes like mine are there overall plus of course almost no parts for it available. Sometimes it is just like having a toddler, just born - in your hands. I saw a lot of videos where people are swapping only one colortune on hot engine regardless so I'll try not to break the head I hope. First I'll just reverse mixture setup to one from service manual, because on current "vacuum cleaner filter" setting idle is just gone I won't be able to adjust without touching throttle every split second. I'll order one plug for me I just want to make sure she will be okay.

EDIT:

I played with mixture screws by ear and I noticed that when I tried turn the screws right to tighten pilot screw it just was dying even faster. So I started turning each of the pilot screw left until engine stopped accelerating. In case of typical communist carburetors turning pilot screw in was riching the mixture and turning it out was leaning mixture. I don't know if jap carbs have it reversed... Idle rpm is little higher than in video update after I found the best point in turning pilot screws by ear. Going below 1200 ish rpm still results in engine just dying without a warning. For now it will be fine, first gear clunks no matter of I had 1000 or 1500 so... I will fine tune this with set of colortunes after this season when I will be able to buy set of 4 from my tools wish list.

[Gorminrider]

Some manuals have very good "cut-away "diagrams of the carburetor and these will help to better understand just what adjustments do.
For instance, you can see from a diagram that you are closing the idle passage by turning it in (clockwise). Notice how important a clean idle jet is, where gas is drawn up and mixed with air. ....I hope one of your mechanics cleaned this. Otherwise you will find yourself trying to adjust the throttle plates individually to compensate for the lack of mixture being delivered at the idlemix screw....
idle circuit.jpg

[tom203]

I'd save my money and skip the colortune- you don't need it.
You need to dismantle carbs yourself and know for sure what jets you got in there . Clean them properly, bench sync to get then close. Then get a carbtune or equivalent ( maybe $100 ?).

your three "mechanics" have made a mess of things -

[Gorminrider]

...and don't forget Mechanics must pay the rent. Fiddling with 34 year-old carburetors and an owner who doesn't have a lot of money may not be viable for them. That said, they will still be helpful for things like tires sprockets chains and more...things that haven't changed in those years.


Buying a 34 year old motorcycle that needs mechanical work (and an oddball one at that!) means you must accept the difficulties yourself.

[2BRacing]

.. I ordered MEIWA filter from Japan and installed it previously soaking it in Bel Ray air filter oil like the book says it should be moistured in oil. With vacuum cleaner filter and MEIWA now she just won't hold idle, it is GONE. ...... So, nobody in my city can fix this, then I need to fix it myself........

Yes, the best mechanic is yourself - take time to read technical threads on this forum and do it yourself, then you will know it has been done properly!

I think your idling problem was caused by the part in bold above: the oil filter must not be soaked in oil, it should only be lightly oiled. For example, sponge filters must be squeezed out after applying oil, so that only a very light coating of oil remains.

Your bike has CV carbs. A few very experienced members on this forum have reported that they were unable to see the clear change between rich and lean using a colortune plug with CV carbs. However, they were able to see the change clearly on VM carbs, which means that CV carbs just do not give a clear signal on a colortune plug. So I would not recommend that you spend money on even one colortune plug, let alone 4, because you will not get the results you expected.

When you turn the idle mixture screws clockwise (right), you are closing the screws, so making the idle mixture leaner. When you turn the idle mixture screws anti-clockwise (counter-clockwise; left), you are opening the screws, so making the idle mixture richer.

Turn each idle mixture screw clockwise (right) gently and slowly until it reaches the bottom (do not force it), and then turn them out (left) three full turns (6 half turns). This setting may be slightly rich, but your bike should start and run on this setting. Turn each screw in (right) slowly a little bit at a time, to the point where the idle speed is highest. You should not have to turn the screw in more than 1 full turn from the 3 turns out starting position to reach this point of highest idle speed, otherwise something else is wrong with your carbs.

Good luck!

[Himer]

@2BRacing. I have written that wrong, used wrong word. Air filter was moistured, not soaked and poked into the aribox. So I learned something new from previous post. So actually my mechanic just made extremely lean mixture in that case. Screws were just tightened when I started adjustment. I made 1 and 1/2 turn on all four carbs and that made her stop needing throttle to start and she keeps idle quite ok. I only don't understand why idle keeps dying when I turn on front light, without light she works. Can additional fuel filter make that mess? previous owner put secondary fuel filter, but for what I am guessing. Tank is really clean, so the mesh on petcock. I'll cut new fuel line without secondary fuel filter and see if there are any changes. Meanwhile I'll go and start from scratch. I'll tighten every pilot screw and unscrew then a certain value.

[2BRacing]

@2BRacing. I have written that wrong, used wrong word. Air filter was moistured, not soaked and poked into the aribox. So I learned something new from previous post. So actually my mechanic just made extremely lean mixture in that case. Screws were just tightened when I started adjustment. I made 1 and 1/2 turn on all four carbs and that made her stop needing throttle to start and she keeps idle quite ok. I only don't understand why idle keeps dying when I turn on front light, without light she works. Can additional fuel filter make that mess? previous owner put secondary fuel filter, but for what I am guessing. Tank is really clean, so the mesh on petcock. I'll cut new fuel line without secondary fuel filter and see if there are any changes. Meanwhile I'll go and start from scratch. I'll tighten every pilot screw and unscrew then a certain value.

It is not a fuel filter problem that causes your bike to die when you turn the light on. Either your battery is not strong enough (not able to supply enough amps), or the charging system is weak and does not charge the battery fully. When you turn the light on, the current (amps) drawn by the light takes away all remaining power in the system, so the coils do not get enough power to keep the engine running.

I suggest you find a post by member Posplayr and do the Quick Test in his signature, and read about the charging system in the other links in his signature. You will probably have to clean up all your electrical connections and test the output of your stator and test that one or more of the stator wires does not have a path to ground. If the stator output is OK, you should wire the 3 stator wires directly to the regulator/rectifier and add two extra earth (ground) wires to make a single point ground (SPG) connection as described by Posplayr. I have done those changes to my GS850G and it made a big difference.

You should also search e-bay for a SH775 regulator/rectifier from a Polaris 4-wheeler all-terrain-vehicle (ATV) to replace the existing regulator/rectifier on your bike to ensure that your stator can function for a longer time without getting damaged. Look at recent posts by member Steve - he posted links to about 5 of the correct SH775 R/R's on e-bay (beware, some sellers do not sell the genuine SH775 R/R's).

Good luck!

[Himer]

@2BRacing

Whole charging section of electrical wiring has been redone by me, whole new wires 2,5mm square. Stator is used one which has more than 30 years it passes resistance test, outputs 95V on 5k rpm. Combined with FH012AA R/R I have stable 14,55V on 5k, less with lights on idle. I should say way less. Battery is new, Yuasa YBL10-A2(I hope I remebered correctly). Previous battery had internal short and I had less than 13,8V on 5k but due to shortened battery inside and it didn't keep any charge to run the engine. It even runs way underrated fuse, half of spec - 7.5A. I run only on stock lights, nothing more. I have no accessories and no need for them.

I tried third, last time. I had to unscrew 3 turns after topping on each carby. And that even was way to lean for it to run. In aftermath I had to set 4 and 1/2 turn - this is the final setting, after this point rpm goes down and engine gets too rich mixture. I have set 1250 rpm after a solid ride she keeps it with lights on, nothing else to add I think. Her throttle response is... speechless? Is this my motorcycle? I don't remember her going THAT fast. And I can run on certain rpm on low gear without "jumping" right now, she goes very smooth and calm. I used only my ear and screwdriver, didn't have to use colortune it happened.

About SH775. Look I am trying not to be a cheap person but with all the taxes and shipping the used SH775 is way too expensive. Even for me. Used SH775 costs 1/3 of my salary, new one 2/3 of my salary. I am aware of FH012 killing the stator but it was the best I could land hands on in my country. I have spare stators witing just in case, along with the gaskets for the cover.

Anyways, sorry for long response but I had a rainy week and coulnd't fiddle with it while it was wet outside and raining. Your advices helped I got the result. So many good souls here For me? Case closed.

[2BRacing]

@ Himer

Well done! In this video your bike runs great! Looks like you have the idle mixture settings at a good point now for your bike.

I have not followed all your previous posts, so maybe you already wrote about re-wiring your charging section. 2.5 mm square wire is good. Stator output of 95V @ 5k rpm is also good.

Looks like you are all good to go! My son has a 1989 GSX400F (the Katana version with full fairing) with nearly 100,000 km on the clock and still going strong!

[Himer]

You're probably refering to completely diffrent Katana. Mine is Katana also. There was I think GK79A if I remember correctly it was water cooled, also 400 but completely diffrent from Katana on the videos I have showed here. Mine is really rare in Europe. This one's code number is GS40XF. Yes I did create posts about charging system and I partially solved it year ago, but it happened that R/R I used year ago was faulty(severe undercharging with healthy stator) so now I use FH012AA instead and it does the job. Very fun bike to ride, lacking some power in my opinion(it is heavy and quite large for it's class), but she has that something from which she earned eternity untill I die or she dies, forever. I know that when I sell it to someone else, that person will cut it for CR. I don't want that, this katana is almost factory stock except few very hard to see details. And everything works including gear indicator. Her condition for her age - 34 years is really good. When I bought her she was working on 3 cylinders only and had a lot to do. My personal mission for this bike is to keep it running which previous owners failed to do so. I probably take periodic maintenance section too seriously, but yes... Valves are adjusted every 5000, chain lubed in 500, chain slack checked in 1000 like book says. And many other things from that section of the manual are covered in mileage it says to do so. Going that route? I haven't been stranded even once, she just keep going.

Thank you for your help again, it is also good to hear that I felt what was right, it just was

[Gorminrider]

sounds Much better, than first video. Good work, Himer!