kz440 no power mid/high range rpm

Whats up guys? So I finally got my kz440 back together and took it for a spin around the block. Idles great and great throttle response. Low end is great and really great torque. When I gun it mid throttle it doesnt want to go...starts popping/back firing. Stock airbox and exhaust. Im thinking maybe timing? Maybe needs fresh plugs and caps? I dont see any adjustments on the carbs themselves. Just an idle adjustment. Carbs have been cleaned and one new diaphragm replaced because it was torn. Any thoughts? Thanks y'all!

check for vaccum leaks at the intake. Were the carbs. synced?

Carb boots are cracked...but not cracked all the way through. Does that matter? They have not been synced. How do you sync? Vaccum gauge? Thanks AB!

I'm having a similar problem, but only w/in the 3-5k RPM range. It's hard starting, but once it gets going, it idles fine, throttle response is great until it hits 3k, then all it wants to do is die. Any sharp throttle inputs will cause it to cut out, but it will fight through it until it hits 5k, then it takes right off and revs all the way up to redline. I did notice, similar to the OP that my carb boots are cracked, and I have not replaced the plugs or wires yet. Needless to say, I'll be following this post...

Get some carb cleaner with the bike idleing spray around the boots, if the RPMs change they are sucking air. You can bench sync them to get them close, by using a 1/64 drill bit, lower the butterflies on both carbs till there is just a slight tug on the bit, at least the carbs will be close till you can vaccum sync them, you'll probably also have to adjust your idle after this....

Here's a basic way to do it...http://www.youtube.com/watch?v=AS77T2CUsjI

http://www.youtube.com/watch?v=AS77T2CUsjI

By the way, if the boots are sucking air you either need to check that the carbs are ceaded correctly or the boots need repair/replacement...

Ordered new carb boots...$70 . They were pretty bad not cracked all the way through, but on their way.Also one of my jets fell out into the float bowl. That will mos def screw things up! Bench synced the carbs...they were in sync. This is a fun peppy little bike as is...can't wait till its a 100% Thanks for the help. I will let you guys know the out come once I get it back together.

Got the new carb boots on and she runs like a dream!!! ;D

Hey where did you find those intake boots? I'm looking for my 82 kz440. Many thanks!

Honestly I can't remember...too many parts for too many bikes since then...I know they cost over $100 for the pair. Just google it...ton of places selling them. Good luck!