Do old Kz's like to run wide open?

I'm hoping to get a little input from some seasoned kz owners. Now that I have my kz400 up and running I'm starting to test the limits of this bike... I still haven't hit highway speeds yet... This is more of a result of me not trusting my mechanical abilities. This is the first bike I've ever rebuilt (top end and carbs) and the first bike I've ever owned . Now realizing that my rebuit top end is holding up and the carbs are functioning well, I've started to really open up the throttle when a straight stretch of road will allow me. As I'm doing this 3 thoughts run through my head. First, I hope the tires I put on myself aren't going fly of the bike (this sounds silly, but I don't have much experience taking off and putting on motorcycle wheels...but I did it). Second thought is wow this thing is working hard to get to these speeds (it's not running bad, just now that I've opened up the top end and have seen the pistons and cams I can now picture them moving at insanely fast speeds). The third thought is.. hey these bike are made to run like this... just go with it and enjoy the ride.

So my question, is running full throttle hard on a bike and will it eventually shorten the life of a bike.... or did the engineers design the old bikes to ride anyway speed you want? It stands to reason that the faster you go the harder an engine works and therefore you risk messing something up. Then again, It almost feels like it's good for the bike when you really open up the throttle and ride it like you stole it. In my mind it's something like shaking off rust or opening up air passages... I don't know like it might be good for the bike to ride it hard... any thoughts or words of wisdom on this?

Dumping the clutch or hard snaps of the throttle, on or off, that allows jerking at the limits of slack in your engine are not really good for your engine. But, as long as you are not over-reving it, WOT is not a bad thing. Just watch your tach n ride it like you stole it! Also, if you're worried about your work, go back over it and make sure everything is tight. Have fun!

If you installed new rings, etc. when rebuilding the top end you should keep the rpm under 5k for the first 500 miles. After that, running the bike up to redline once in a while before shifting should not hurt anything, but don't drone along for miles and miles at redline and don't exceed redline. Opening the throttle all the way won't hurt a thing. Ed

Thanks for the input guys. Ed I did install new piston rings and have many times gone above 5000 rpms !! woops!!! Now I know to be more careful about that... thanks. Since I've gotten it running I've put on about 60 miles, so I got a ways to go. One other thought, whats a good amount of mileage to check the spark plugs? I've checked them after a couple of miles of scootin' around town at 30 to 35 mph and they seem to run a little rich. Then I'll take a little longer ride and got maybe to 50 mph (not to sure as my speedo doesn't work, my tach does however) and then check the plugs and they seem to be just about right, maybe a little on the lean side... I'll post some pics just to be sure later today. So what's a good distance and speeds to judge the spark plugs more accurately?

If mine I wouldn't worry too much about checking the plugs until after 500 mile break in unless the engine starts to overheat. Ed

Well... oddly enough I do think It started to overheat the other day.. I was riding along fine then it started to run a little rough and died as I was coming to a stop light. Could someone take a look at this pic and tell me if I'm running really lean? It seems the left cylinder (plug on the left in photo) is looking "ok" while the right cylinder is running lean. This leads me to believe it could be a float adjustment issue.

Bad quality on the photo.. had to use my computers camera.

Looks Lean alright. Better find out whats going on there. Check for Fuel level and vacuum leaks.

Motor Head wrote: Looks Lean alright. Better find out whats going on there. Check for Fuel level and vacuum leaks.

Both plugs or just the right looking lean to you? I'm thinking about jetting up but if just the right side then I think I'll adjust the float level height again. suggestions? My float level check is pretty crude... I tried the test that I saw Patton post using just a clear tube.. but inevitably I spill a little bit of fuel and get a bad reading perhaps. I have done a vacuum leak test using carb cleaner but didn't find anything.

Just the one, really. Fuel level is Most Important to having the proper carb function, this needs to be set correctly before jetting. Double check the vacuum leaks also, takes only a minute or two.