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My Kawasaki KZ 550 Scrambler build is finally finished. Thank you for your advice, that i have found here !

I have one more problem tho. My bike goes only 120km/h. I guess it is due to wrong gearing, and different tire size - but can it be such a difference?

Thank you .

Howdy. Something isn't right. I doubt the problem is the sprockets or tire. For curiosity's sake what sizes did you go with?

Awesome job, man! Your bike looks great!

Looks great. Nice side covers.

The bike should go near 190 km/hr (120mph) with stock tires and gearing on level ground with no wind.

The knobby tires will slow it down a bit but not that much.

Are you sure all four cylinders are firing? The spray water test on the headers is the first thing I would try.

I would +1 checking this. I just got back from a ride on my '80 KZ440 and I was doing 75 to 80 mph on the highway easily, so I'd assume if your 550 was firing on all cylinders you would be able to pass that with ease.

I dont really remember now - I'll count the sprockets and write again. I know that the bike should be going faster. It's weird. All of my cylinders are fireing for sure. The bike sound very healthy. Carbs ballanced and all. There is one concern - my clutch feels a bit like slipping (even though i have adjusted it for 100 times - but it not too bad) and also the bike had a really rough life before me - i did measure the compression, but I guess it could be higher. The tachometer shows 11 000 rpm when i go barely 120 km/h on 6th gear. Can it have something to do with the POD filters or the straight flow exhaust ?

Thanks a lot

When a clutch slips, the RPMs usually jump up quickly. Slipping happens most in highest gears.

If the RPMs are truly at 11,000 then yes, either the clutch is slipping or the gearing is vastly different from stock.

Here's a link to the clutch adjustment which is sometimes written incorrectly in some manuals.
s3.amazonaws.com/gpzweb/ClutchReleaseMech.GIF

I think your front sprocket should be 16T and rear sprocket should be 40T.

Sounds like the clutch is slipping, and that could easily be the result of using the wrong motor oil. What oil are you using? Ed

The link provided by loudhvx has the procedure, but I'll go ahead & say you probably need to turn the clutch release adjusting screw counterclockwise first until hard to turn, then clockwise 1/4 or 1/2 turn, then tighten the locknut. It's kind of counter-intuitive. That's how it's done on my 81 650-CSR (the KZ650 manual says 1/4 turn). Of course do the other adjustment stuff at the clutch lever & cable barrel adjuster.

Guys thank you so much for the answers !! As you describe - the clutch slips usually quicky at some point and you do feel it very significantly. I do not think that it slips at the high speeds. And I did adjust it exactly according to the scheme you've sent.

I'll let you know about the gearing as soon as I am by the bike. I have a feeling that i have 16T and 43T. The oil issue could be possible - i am using a fully synthetic oil - the one that is written on the oil cap.

BUT i checked my old compression pictures and the numbers are terrible :/ from 80PSI to 140psi. I did cranck it without motoroil in the sump - I just sprayed about 50 ml each in the cylinder from the top. Which isnt ideal ... i know.

Could the low top speed be caused by low compression ?

Are you holding the throttle open when doing the compression test? Also make sure there is a valve in the end of the compression hose that you are using.

I did the compression test a loooooong time ago - about 3 years. But i think i havent hold the throttle open.

What i would like to add - the bike had a really rough life before me. I would not be suprised if it would be running low top speed because of some engine damage.

But it runs sweet otherwise. That is what's weird