Kick stand switch can cause all kinds of problems if faulty. Usually bike won't shift into gear tho. Coil failure would not show the issue you are having. You would have significant cut out and likely backfiring. A totally bad coil and you would be running on 3 cylinders. None of this lines up with your problem. A faulty pick up coil also seems unlikely. They can go intermittent but symptoms would be different than what you are experiencing.

It really doesn't sound like an electrical problem. To have only one spot where the problem shows up very rarely would be electrical. Flat spots are almost always fuel related. The fact that after the jet and needle change that the problem hasn't changed (gotten better or worse) or at least moved in the RPM range is quite strange tho.

 

yeah this is really confusing me! ... Im doing a lot of reading on other forums for "motorcycle will not rev past xxxxxrpm" and there are hundreds of results... the ones that got resolved by way of jetting/air filter/fuel pump or anything fuel related all have one thing in common, the bike will not go PAST that rpm point at all apart from neutral. In my case, if i downshift and get the revs up, it continues to accelerate to i presume redline... this continued acceleration though is not smooth and a slight misfire is apparent.

I have experienced one proper full power pull from it yesterday, first ride out after the jet kit and im rolling on the power in 1st gear and i hit the rpm wall, then im pretty sure i hit a little pothole, and then it spun the rear tire like it was nothing and it even sounded much strong (a 4 pots firing proper) .. but then after going back to idle it was back to the usual issue...

being such an old bike, with 20 previous owners, im gonna take all the coils end RR of to generally test and give them a clean as i think it cant hurt and it deserves it

I had fueling issues on my bandit 1200 while i was playing with the carbs, but it never felt like this.... the best way i can describe it, why i "feel" like its a leccy problem is it feels exactly like driving a car or bike through a massive puddle of water and u have crappy HT leads... it just pops and stutters... it feeeeels like a misfire due to a loose/rotten connection somewhere....

i do value your help tho Dennis and i did read one forum post where the symptoms where VERY similar and he had put the airbox back on wrong after some work and blocked some air inlet (not a honda) .. it was running WAY to rich! ..... this may hold some water so to speak as the only fuel thing i havent changed/touched is the air filter! it doesnt matter how many holes i block/unblock if the filter is the restriction. Im gonna play devils advocate and run for 2 miles without it after i sort out the current misfire issue since i touched the coil, and see if that makes the issue at least change rpm or something different!

Its gonna be a few days till i can get some more wrenching time on it, but i will keep this up-to-date as and when i do. Thanks again mate!

 

What's really weird about this is that each time you describe the problem it sounds different. If you hit a pothole and it took off, then you have a short somewhere. Suspecting individual components like coils etc., is a waste of time.

More commonly the ignition switch can go bad. Wiggle the key while riding and see if anything happens. The kill switch may also be causing this. Take it apart and clean it. The stand switch as you already know. There could be a wire in the harness that is rubbing on the frame. Battery connection and wires. Are they tight? Are the cables an wires in good condition? You may have corrosion in a connection somewhere. All the plugs, sockets, and fuses should be looked at for corrosion or heat damage.

You may have a rectifier failing but have never heard these symptoms. Have you done the electrical system checks. Is the battery good and holding charge?

 

Every time I get on it to test its true it sounds different. I think cause I try and think of more things it could be when the previous attempt fails! Esp now after jetting and needles my mind was trying to pickup another lead to go down.. I think next time I test I'll get the go pro on the helmet or mount it near the engine so its clear. I just started it in the garage for 30 secs to see if all the headers got warm.. Only 3 did. Cyl 4 (throttle side) was stone cold.

 

One of the keys to successful trouble shooting is to be in tune with the effect of a change. That's why earlier I asked whether the flat spot moved at all after the change. It's also important to only make one change at a time so you know what's going on. Multiple changes can make it impossible particularly when things go wrong.

While you were engaged in the tuning process you decided to start looking at the CDI and now you have a completely different problem with the engine running on only 3 cylinders. Your also looking at coils and pick up coils and all sorts of things that probably had nothing to do with the original problem. It's very confusing to follow and so outside of the proper way to do things that I frankly have no clue what to tell you to try anymore.

Like I said earlier, it seems like each time you describe things it's different.

I'm sorry to sound so blunt but my suggestion would be to slow down and think through what you did that changed it and retrace your steps.

I also see you are on the Facebook CBR page. There are a lot of people on there that have no clue what they are talking about. This is true of most of the web, which I read in many of your comments about things to check that you "read" on the web. One of the keys to using the web as a resource is to know the difference between crap and fact.

I've been working on cars and motorcycles for over 50 years, and still learn new things everyday but I also know enough to not get suckered in by the people who have zero experience and had one problem with their first bike that they consider to be the explanation to everyone else's problem.

 

I know about taking things with a pinch of salt from forums, but thats why im keeping this up to date, as you know ur stuff and i appreciate your comments! Im reading others for ideas on other avenues i can go down in case its not the carbs...

It keeps sounding different, cause it does something slightly different each time. For example the last time it went and shot off like a rocket and it sounded perfect, this makes me think the carbs/air filter etc is ok and had to be electronic as it was like a switch from stutter to full on smooth power! but then again it this is where troubleshooting experience comes in handy. So after reading your comments and not really touching the electronics (just unplug and plug in the cdi) i am gonna continue on the fueling side of things.

I took No 4 plug out and its sparks good and proper so electronics are i think not the issue (or at least i shouldnt be looking there for now) as you rightly suggested. Started her up with a lot of choke and cylinder 4 does fire, but not as strongly as the other 3 until its warm enough to turn off the choke. So this to me sounds like 4 is too lean on idle mix (they all have no38 pilot jets). after i let it warm up i did the water mist on the headers trick, 3 and 4 sizzled off real fast, 1 and 2 not so much (i have carb balance adapters on the way, and i think a sync might sort that).

The thing i noticed that might go against everything i have been trying to do, is that the stuttering gets worse as it gets hotter, And since i have put the needles in, it puffs black smoke when i give it a hard blip on the throttle. The plug i took out of number 4 has only 25 miles on it, and it was pretty black. When i changed jets i did noticed that the DJ120's i put in were visually the same size as the ones i took out (most prob drilled by PO).. Could it be that its too rich after all? i have a range of dyno jets i can play about with so making it leaner shouldn't be an issue.

While revving it up in the garage, i did notice that the slides flutter a lot, even holding mid range revs, is this normal? i remember on my bandit the slides moved up and down very smoothly. Video: https://www.youtube.com/watch?v=vvxcBY0zY_M

Also i made a video which shows the 5k issue.. In the garage i can power past 5k with no problem, but holding it there u can hear a very definite change of tone in the noise its making: https://www.youtube.com/watch?v=V7bjglclTcc

Also one more vid of general idle/throttle response which is pretty good (better when cooler) : https://www.youtube.com/watch?v=pNVvv4rt6OY

Again, i do really appreciate the help and will try to focus and keep on track. Plan now is to balance them when the tubes arrive, and maybe drop down to more original sized jets?

Thanks and sorry for the long post!

 

What's that jumble of wires?

I'm going to slow down a little here.

The slides look okay. Balance may be off a little. You can't really tell much by looking at the slides.

The fact that one carb is not fueling at startup should be a concern. Is that the carb with the broken pilot screw that you had trouble adjusting by chance? If not you likely have a plugged pilot jet. Where's the dirt coming from. The throttle response vid also is indicative of pilot circuit out of whack. It's not making the transition from pilot to mains. Also, if you left the stock pilot jet in when you upped the mains, you may not be fueling quick enough at the transition because the pilot circuit is lean.

The 5000 flat spot does not sound like it's really at 5000. It sounds like it's shuddering all the way up which is also indicative of a funky pilot circuit either dirty or not adjusted right. I was concerned when you had an issue with that pilot screw. The pilot circuit provides a portion of the fuel all the way through the throttle range. If one carb is out of adjustment it will mess up the works because it will want to run faster or slower. This may explain the slide flutter your seeing also. Everything has to be tuned right for the total system to work right.

One thing that seems to connect the dots for me is dirt. Are you sure your not getting dirt in there somehow? The reason I say this is why did it start running crappy after you played with the CDI? Why is it cutting out and coming on suddenly? This is something that happens when dirt gets in. Small particulate gets in then clears out. If tank is clean and you have a filter on it then look at everything on the other side. Maybe the hoses are old and breaking down. My guess is your getting dirt in from somewhere. I would also fix that pilot screw.

 

Solid advice mate!! u are correct.. the number 4 cylinder was bone dry when i checked for spark.. however this cylinder does fire once warmed up.. im gonna get that screw out completly and use a dremel to cut a new notch for a flathead driver.. just the 4 little towers that hold a cross head driver broke. the actual internal bit of it is to my knowledge intact...

So new plan.. re-tape up all the holes on the airbox to get it as stock as possible. Then put close to stock main jets in, stock needles, and clean all 4 pilot circuits, esp the broken one... that way ive got everything stock apart from the exhaust and i can work from a solid base, cause to be honest the big jets i put in it where the same as the ones i took out (PO drilled them im sure) so all ive done is made it rich on the transition with the DJ needles, which you notice is messed up!

 

That sounds like a good plan. Inspect very closely for dirt in there. I still think that may be an issue also.

 

I'm back with the cane!! Had some time finally in the garage and I've changed the jets to dynojet 98 mains. I put a piece of hose tight over the pilot jet and blew as hard as possible and air came out the little hole in the carb throat as well as a hole airbox side. I removed the broken screw and notched it for a flathead driver and it turns very well. It doesnt seem to screw in as much as the others but anyhow its clear inside. There is the little o ring behind the washer, then a spring. All looked OK. I put the carbs back on the bike and inspected the fuel line from the tank, decided to cut the ends off as they expanded a bit so now its nice and tight. Fired it up and started very well.. All 4 header pipes got nice and hot at the same time on idle.. It sounded a lot better! Didn't have time to put it all back together and make a test ride.. That's on Thursday .. Here is a vids to compare to the other one, sorry its so dark, but its the sound that's important. Let me know if you can hear anything wrong thanks!!

https://youtu.be/AX4y2bGvcxs