Hi Keith, as Kevan said below. Your actually carrying out completely the wrong process for carb set up, the screw your adjusting is not for balancing you must also guarantee no vacuum leakage in particular the nipple take of on the carb for the vacuum fuel tap if it has one. This must be capped of. I know you have a manual please follow that it is easier than me typing. Your getting closer, please remember the fuel screw underneath the carbs and the air screw work together. Also its good to remember your measuring vacuum in front of the slides towards the engine, its the final position of these slides your trying to equal out with there adjusting screws. No Vacuum leaks or the test is useless. try this to start and keep going your doing great. 5/8 turn out on fuel screw from lightly closed and 1.5 turns out on air screw. I second colour tune to but you still need to know what colour to aim for, blue with very light flickering yellow is close on these old dinosaur carbs.

Keith, what Kevan said. +1 for the colortune

Only just found this, really helpful, i have bought an old hardtail chop with a kz650 engine, was running rough when i got it, bunged a new set of plugs in and that improved it a bit, carbs were flooding so i pulled them off, stripped and cleaned, new float valves and set float heights, it's rideable but still rough, i hooked up the vacuum gauges and have the same readings as you, same red section, have been advised to replace the carb to head mounting rubbers so got a set ordered, also been advised that because my bike has pod filters and custom pipes it will never run 100%, only as good as i can get it.

Keith, another great vid! So look forward to seeing them. I think you should ignore the writing on the gauges and balance the carbs, so they record very similar vacuums around tickover rpm, maybe slightly above. Blip the throttle to see if they settle. Balancing should be done via the top of the carb and adjusting the screw under each top hat by loosening the locking nut. Do not balance them with the airscrew. The carbs look fairly even for now. A bigger difference is setting the airscrews properly with a colourtune - sorry to bang on about it, but it will transform your bike far more, compared to balancing carbs with vac gauges. It will affect starting, tick over, and the first hit of the throttle. It's about £35 from a number of re-sellers. If you colour tune each cyl ( it's really quite quick and would make good video) and it's still playing up then start the timing detective work, but first colourtune it, I beg you!

Hi Keith just some quick observations as others have said you balance the carb slides not the air screws but they don't look too bad to be fair however the lack of movement on number 1 gauge would suggest a misfire on that cylinder maybe try a fresh set of plugs ! Also your exhaust blow this may sound mad but do you have the correct cam cover gasket as American Market bi,es had exhaust gas recirculating valves in cam cover and gaskets are slightly different go on ask me how I know cheers mark

I'm from the states and have been around these bikes since the 70's and have never heard of a coulor or color tune, am I missing something here. Could someone tell me what this is. Back in the day when I was having all kinds of trouble with my kz650 running good everyone said check the rectifier to see if it was putting out the right numbers, I checked everything and finally the bike shop said it was my coils, they were new ones to start with but they put on another new set and dialed everything in and it ran better than it ever had before. I believe that you put new coils on it already, have you checked valve spring pressure? Or make sure that a shim hasn't came out. Just hang in there it's getting closer. Thanks for the video.

If You haven't cleaned the inside of the exhausts already, I would suggest that You do it now with some strong soap or lye, though that probably has nothing to do with the start up problems. To me, this sounds more like a timing/jetting case. Two questions on my mind: So, how does the spark plugs look like after a good warm up run? Take them out and put them on the work bench so You(we) can have a real good look at them. Do they look like it is running a bit lean? Advancer? Did You change it, or is it the old one? Although the coils on the timing advancer springs are in an almost fully relaxed position when stored for a longer period, the eyes of the springs still are under constant stress. They could have been stretched beyond specs? How about taking another compression test after these first small runs? Just to eliminate any shimming issues? Strange, that the exhaust on number one still blows by the gasket - if I understood You correctly? It should be sealing now, with new gasket and correct torque? Are You running out of threads on one of the exhaust studs - so that You can't compress the gasket enough - but the torque is still there, because of the nut bottoming out, or running out of threads? Maybe try two gaskets on that port, so You have more threads to work with? I like to use a tiny amount of silicone sealer on the gasket, just to fix it into the port before mounting the pipe and flange. It ensures that the gasket doesn't move as You place the pipe onto it. I usually like to wait a few hours before torquing the gasket down, so the sealer isn't totally squeezed out from there. Anyway, it's good to see You hanging onto it, and really trying to solve the small issues still left. It's hard to tell from here, if it is running lean or timing out of specs, so that would be all upon You. I can't give You anything but general advice, and often they are so obvious You've probably already checked it out. I'd still like to see those spark plugs, though. Hang in there, You're getting closer and closer! Good luck! 👍

Looks like this is one stubborn KZ, but I would count this as progress non the less. Having said that, the exhaust leak is definitely a problem and a contributing factor, that needs to be sorted out. These motorcycles are very sensitive to any inconsistencies between either exhaust or intake. Perhaps disconnect all the exhaust headers to equalize them and see how it affects the engine? Also spray some carb cleaner on the intake boots and carb holders while the engine is running to see if there is any change in RPM, if there is, you have a vacuum leak. These motorcycles simply do not tolerate any sort of vacuum or exhaust leaks kindly. I have not seen your video of installing the carb holders, but they are notoriously difficult to get a proper seal on. I used a bit of RTV to get them to seal properly, not sure if you used any type of sealant on these. For the synchronization, as I mentioned in your previous video, you will get very close with a bench synch on these and that looks to be the case. The air screw you adjusted will not affect the gauge reading and I would ignore the text on the gauges. It may be accurate for some setups, but not on this one. All you need to check is that the readings are about the same. To adjust the amount of vacuum being pulled, you need to remove the top cap of the carburetors and adjust the nut that connects to the linkage arm. That's how you synchronize these.

Sorry, but get a morgan carbtune, if doing the sync process.