TOPIC:

Sorry in advance for the length:whistle:

I have a 1979 Kz1000st,when i bought the bike it ran pretty good and needed a few parts. I did the regular tune up stuff like oil/filter spark plugs, but nothing to the carbs:unsure: I'm afraid to. So I see the ignition wire has a break so I replace them one coil was replaced before as the wire screws in, the other I had to use ngk splices. The bike now runs about the same no better no worse. I drive it about 20-30 miles off and on all of a sudden the thing is gutless seems like it is running on two or three cylinders. I forgot to mention when it is warming up it almost sounds like mini backfire out of the exhaust, it seem to go away during city driving but at about 60kms and about 4-5000 rpm I can throttle it wide open and it bogs out. I pulled the plug wire off of #2 cylinder and the motor runs about the same, checked for spark ok put in a new plug still crappy, so I do the same to #2 plug same thing.
When I test for spark I can hold the boot with the plug in it against the block and the spark snaps and jumps from the ground on the plug to the block but when i totally ground the plug there is only sparks around the center electrode of the plug it doesn't seem to go to the gound of the plug. The bike I was told are powerfull but this here baby is like a vespa:angry: My plugs are very black, I know carb work is in the future but the bike worked fine before. I seem to think it is a electrical problem and it doesn't have points or a condensor. Any help woild be great if only one small part of my problem

Fouled plugs. Re-do your spark check with a fresh set. If that seems okay, try running on the fresh set. If it runs okay and then goes asthmatic within a few miles, your problem is more likely mechanical than electrical. Do a compression check. Anything less tha 130 or so per pot means your valves might need adjusted, or your rings or valve seats are a little tired. Your carbs could also be dumping gas - you didn't say whether your current plugs are *wet* black or *dry* black....

They are dry black and sooty

My first thought was poor compression too. Poor compression = incomplete combustion = soot. Maybe its just a bad gasket.

2bskor wrote:

They are dry black and sooty

Well, the good news is that your problem is still most likely to be either carburation, ignition, or a bit of both...

Doesn't sound like leaky rings or valve seals or guides is a problem as yet.

Dry, sooty black is carbon fouling from perhaps any one of or a combination of the folowing:

Your carbs could be running way rich. Could be merely an adjustment, could be time for them to be cleaned and/or rebuilt.

Your plugs might be too cold - NGK B8ES is the spec'd plug for that motor.

Your coil(s) might be getting weak.

You didn't say whether you were running a points and condenser or if at some point somebody upgraded it to an electronic ignition.

If it's points/condenser, a new set of those might be in the cards as well. The spark advancer plate behind the poinst might also be sticking - they have a tendency to rust a bit.

There's a few ideas to poke around with...

Ok here it goes:whistle: I took the carbs off and cleaned the frig out of them I didn't actually disassemble them other than the top and bottom bowls. I sprayed every hole I could see the floats the needle or springy whatevers the jets put new o ring on the drain plugs etc. I put hotter ngk plugs in a new fuel filter and new gas. The bike seems to run smoother and it doesn't seem to spit as much. I can still hear the left carb spitting or missing and there seems to be a slight ticking sound near the valve cover on the same side. What about valve adjustment ?? I only ran the bike in the driveway for about 5-10 mins I pulled the plus and there was hardly any carbon, not a good test yet though a ride is the true test. Any more ideas would be great:)

2bskor wrote:

I took the carbs off and cleaned the frig out of them I didn't actually disassemble them other than the top and bottom bowls. I sprayed every hole I could see the floats the needle or springy whatevers the jets put new o ring on the drain plugs etc.

Well, that actually isn't a carb *cleaning*, it's more of a nickle tour. At the very least a cleaning requires pulling, cleaning and visually inspecting the pilot and main jets, etc. Look around the fils section and search the forums for *anything* on carb cleaning by Wired George; he knows carbs, I'm just a ham-handed weekender...

I put hotter ngk plugs in a new fuel filter and new gas. The bike seems to run smoother and it doesn't seem to spit as much.

Cool.

I can still hear the left carb spitting or missing and there seems to be a slight ticking sound near the valve cover on the same side.

The spitting may be air leakage somewhere along the rubber plenums between the carb and the intake port. It may be dried out and cracked, or leaking in at the mating surface with the head. Some use a *very light* finger-swipe of non-hardening silicone on that surface...

What about valve adjustment ??

The short answer is you can *NEVER* have your valves too (properly) adjusted. That also may be a source of combustion problems, as well as that ticking noise. Again, keep an eye out for tutorials by Wired George, and you won't get steered wrong.

The good news is that if the motor has quieted down enough for you to start hearing the ticking, you're heading in the right direction...

I only ran the bike in the driveway for about 5-10 mins I pulled the plus and there was hardly any carbon, not a good test yet though a ride is the true test.

Well, at least things seem to have improved. A good half hour run will tell you a lot more, but you're a step or two away from that yet...

Any more ideas would be great:)

There you go....

2bskor - First, approach your poorly running bike methodically. You first need to check compression. Have you done that? Then, if there are compression issues, you will really need to check valve clearances. If those check out, you will need to do some checking to see if you are getting 12VDC at your coils. If you are serious about running this bike, a new set of aftermarket coils and 12VDC will go a long way.

Problem is, with your electronic ignition, you not only have the igniter but an inline resistor that power passes through to feed the coils. Most of the time, it has been my experience, the resistor gains a lot of resistance over time. You should check its impedence and the primary impedence of the coils. I BET they are both much higher than they should be and your spark is poor. If you need help with this, let me know...

Last, you are probably correct in that your carbs are a problem. You can't clean them unless you have the know how and split the rack if you do it yourself. If you need help with the carbs, let me know.

You probably are facing problems in multiple areas and I would strongly advise to work through the steps in the order I suggest otherwise you will just waste your time.

Well either my "nickle tour" carb cleaning adventure or putting hotter spark plugs or draining the high octane gas and putting in regular or the new fuel filter paid off the bike seems to run a ok not like a vespa scooter:laugh:

Thanks to all for the info nad keep up the good work !!