TOPIC:

hello mates, im a newbie on the forum, but not so much about bikes.. this time i need really help. first of all sorry for the poor english!

i hate her. damn!!!!!!
the strory is......
i had the old 550 with lack of compression, so i decided to totally rebuild the engine.
new things i did:
piston rings
lapped head
head gasket (yes i RE-thightened the head !)
base gasket
valve lapped
cam chain, bearings, oil seals.... ALL!

triple checked the valve timing, i'm sure it's correct.
triple checked valve clearance, it's ok!
compression test - HOT engine: 170-175-175-175 PSI

ignition coils tested: correct ohms in both windings.
pickup coil (has a broken magnet) but value ok.
igniter show ohms values according to manufacturer manual.

CARBURETORS:
i'm ***king sure they are TOTALLY clean, totally stripped, ultrasonic bath, boiled in vinegar, new orings in the fuel line. BENCH synced.
i clean them million times. pilot circuit is ok.

new spark plugs D8EA.
new ignition leads, NO resistor tipe.
new plugs caps NGK 5 KOHM
new battery

basically, the thing that happe its the same problem i had BEFORE the total dismantling. haunting me!!!!!!
when i start the bike, the idle SUCKS!!!! really, it was like a old clunker with seized rod.. TA_TAAM_TATA_TAAAM . ok, i think ''i have just to sync her'' but, EXACTLY AS BEFORE , when i put the vacuum gauge hoses on the carburetors port, it simply doesn't work , the gauge random stop rising on one or more cylinder.

i'll explain better:
the engine start with NO difficult, then i press the choke plunger in. the idle is almost impossible to achieve: she floats between 500 rpm and 1500 rpm.
when i try to turn the gas, she seem to die for a moment, then i can hear a perfect engine that accelerate perfectly!!!! i can hit5000, 6000, or 7000 rpm with no problem.. .and then when i close the gas she drop to 200 rpm and seems to die, if i don't touch the gas. if i touch the gas a little the idle return to 1300/1600 rpm.
i cant reach a lower idle.

why this bike is so impossible to sync?
why sometimes i can read on the vacuum gauge all 4 cylinders are pulling 24 cmHG .... and just a second after two are to zero

i suspect this can be a spark problem, but i can't find a real guilty. the spark i see are not the best i have ever seen, but there is at least spark.

the only things i think possible, after i have rebuild a whole bike and triple tested all, is that when at lower rpms, the ignition system doesn't work as it should.. is this a valid theory?

i have on this bike the same problem since 4 years. i can't get a decent idle.., or (the most terrible thing) a smoot acceleration in the moment that is the transition from idle to just 1800/2000 rpm and higher.
i have to definitely rev her up to make her work properly

help, please!
.

What year and model? Since you say choke plunger, I assume you have a later model with TK26 carbs. It would be easier to help if we know what carbs you have.

Have you taken the pickups apart? I assume you did if you know that one magnet is broken. IT can work fine with a broken magnet, but the magnets have to be installed the correct way, and must use the brass screws in the right place.
gpzweb.s3-website-us-east-1.amazonaws.co.../PickupAndRotor.html

24 cm vacuum is right on. But if two cylinders drop to zero, you have to find out why. That should not happen. Even a bad vacuum leak won't cause that to happen.

Your compression numbers are very good.

First thing, though, is you need to know which cylinders are not firing. Exhaust temperature is a good indicator of this. You could try a non-contact infra-red thermometer, but you have to play around to get a feel for how to use it, how to aim it etc. You could try the spray bottle with water. Seeing how fast the water boils of is a good indicator.

Once you know which cylinders are failing, then you simply swap ignition parts around to see if the problem follows the swap. If it does, then you have an ignition problem. If not, then it's carbs or motor.

Since you say this is the same problem you had before all the work then i would say its one of two things..first..check the carb maifold boots. while its running spry some carbcleaner around them ..if the idle changes then thats youll know right off thats your hucklberry..
otherwise..im betting its a ignition (coil,pickup,and or advance issue)

thank you.
she is a kz550h1
tk 26 carbs, right!
intake boots.. i suspected intake air leak, so i bought new intake boots.. and no, this is not the problem
the magnet is broken, i open it to check, but i start wondering if the broken magnet change his polarity (i have to say i lubed the pickup cam on the crankshaft and its free, smootlhy)

i have a infra red thermometer, after 5 minutes running in those conditions my temp was
200/220 c° cylinder 3 and 4-
80° cylinder 2,
90/110 c° cylinder 1

i can't explain why during the symc, for a pair of minutes i can see all cylinders working, then.......randomn one or more drop to zero.

i'm very, very, very disheartened.. alot of work, total rebuild, still the same old issue

and again, i have all ignition system in specs, but for some reason i don't feel it necessarily mean that they are ok.

my bike use TEC zc006-tr12 ignition coils, can i try with gpz 900 r coils?

I'm with Loudhvx on this one. I was surprised to learn that my bike ran so smoothly on two cylinders. I did not realize that I had completely knocked the power wires off of the right side coil installing the tank so many times. Similar to your symptoms, it would start, not low idle well, a bunch of funky noises and gasps, but would rev up smoothly. When I replaced spark boots and hooked the coil back up the thing purred and idled like a kitten. I have know idea why it runs on two cylinder, but it did. I vote electrical, either coil, plug boot (they do fail) , wires or the magnet induction unit. Also did you have to derust or disassembly the advancer? If you did take it apart (springs, arms and bearing) be sure it is not 180 degrees off. I did this and it would absolutely not run right. (go figure) Keep trying you are close and is sounds like fuel and air are not your problem given the compression numbers and rebuild. That leaves electric/spark left. Good luck! R

the worst thing is this vacuum gaugedropping to zero in one or more cyliinder while the engine is still running !!
i suppose: if the , for example, number 2 cylinder iis STILL moving (even if not fire) how is possible i have no vacuum reading?

Yes that is goofy, the only circumstance I can think of is a piston trying to compress a open valve condition, which would be timing. Could a cam ave been been installed improperly? I also though it was odd your misfires (based on pipe temp result) are on cylinders from each coil.1-4 and 2-3 fire from each respective coil. R

Hum, you are right, but i think that in a improper timing problem, its difficult to See 175 PSI with hot engine !
And this vacuum reading problem is absolutely random: sometimes i read up to 24cmhg, sometimes it stop to read , what a mindfuck

Just a simple thing as help here on a PC is difficult, but you do have the coils hooked up correctly? Lside 2-3, Rside 1-4. I was looking through the manual and it has no good reason for intermittent carb vacuum. With TK carbs and good cylinder compression I cannot fathom how that is possible. Bad manometer? Check coil wiring and spark boots with a meter. Also when testing cylinder compression in individual cylinders you have no idea on timing stroke and if the compression is being built at the right time. 180 degrees off is common and at least each separate cam shaft could be right half the time. If your exhaust cam is right it could build compression and the intake could be off?/? Maybe?? R

Yes, yes.. I have left coil for cylinders 2 and 3 , right coil for 1 and 4.
I have just tested my plug caos, they are all a bit over 5kohm. One is to almost 7 kohm, but..damn, can this be aproblem with so terrible sympthoms?

I wouldn't think so and the plug boots should be find as long as they have connectivity. Zero carb vacuum WTF how does that happen?

R

Can you get a video of wiring and an attempted start run up to UTube?