TOPIC:

Do you have experience on any other inline four? Does you bike rev similarly?

Do you have a video of it revving so we can hear it near redline?

If you are getting near redline in top gear then engine condition should not be an issue regarding the top speed.

Low compression numbers can be from an incorrectly designed tool. That is very common nowadays, especially if it's from Harbor Freight.

Frenkie S22 wrote: .......... The oil issue could be possible - i am using a fully synthetic oil - the one that is written on the oil cap...........

Sorry, but that tells us nothing. There is fully synthetic oil that works great on bikes and there is fully synthetic oil that will quickly ruin a clutch. What SPECIFIC oil are you using? Is it JASO-MA compliant? If not the oil may very well be the reason your clutch is slipping - and it IS slipping. Ed

Thank you so much for the answers. I am very sorry that I cant give correct information right now because I'm not at home where the bike is currently.
The engine oil that I have used is a Valvoline 4T SYNpower 10W-50, JASO MA2 fully synthetic oil.

So I did count the sprockets: the bike came originally with 16T / 40T, I bought a new set and that one has 16T / 41T. I couldn't get the one with 40T anywhere in the Czech Republic. But I thought that it shouldnt make such a difference.
The tire itself is much bigger in diameter than the original one - I'd say 2cm in diameter.

A clip of my bike reving is here: (high idle tho) but to me the reving seems just fine.
(one random thought - the mechanic that you see in the sync picture) did play around a lot with the ignition advancer - on the right hand side of the engine. It was super rusted. And I'm not sure that it works correctly. Might be the issue...

I dont really have experience with other 4cylinder bikes. I play around with cars and 2stroke motorbikes a lot, but i have never ridden another 4cyl bike. What makes me think that everything is right is the fact, that during the carb ballancing process the indivdual carbs were all equal etc.

MAYBE I'm just gonna try to put 2teeth bigger front sprocket and try what difference it makes. What do you think? I did a bit of research and the stock sprocket size on the KZ550 was 16T/38T which means gear ratio of 2,37. With my setup now it is 2,56. With the 18T front sprocket (cheaper than buying rear) it would bring me to 2,27 which would also compensate for the tire size and might get me to stock figures.


Thank you again for HELP

I try to watch the video when I get home. (It won't play at work.)

One tooth difference won't make much difference. I wouldn't bother changing the gearing. Trying to fit an 18T sprocket in front might be difficult because there is a sprocket guard. The chain might rub on it. Either way, I doubt your problem is gearing.

Thank you for the answer - In the video the bike doesn't rev all the way to redline. But this is the best video I have right now.
Here you see it going - at this point the clutch was badly adjusted so you hear it slipping. It doesnt do this anymore.

In the reality the difference to stock is 3 teeth on the rear. Stock should be 38T.

And yes - I am afraid that the chain is going to rubb on the guard with the 18T front sprocket - but the part was specifically meant for KZ550 1982 so I kinda blindly believe the manufacturer, that it should work.

I have already ordered it because it was cheap and I want to try what it does. I did some maths and it should increase my top speed by 12% which is 134 km/h. But that still isnt enough :/ To be honest I actually don't seek for higher top speed, my usual travelling speed is about 120 km/h but I would like to lower the RPMs in orther to keep the bike at a healthy range. It just seems super strange that it goes so slow.

What else could it be ? I'm completely out of ideas. The bike has new spark plugs etc, Could the ignition advancer be installed wrong, is there smthg you can adjust on it? ?

One more thing - the oil pressure indication turns on when ideling now. There is enough oil and the bike still runs the same as before. The indication used to be fine, but now it strangely turns on by low rpms.

A 18T front sprocket need more engine torque and effect more clutch slippery!!!
You have to confirm your ignition advancer mechanism is oiled and moving freely.
If the oil pressure indicator light turns on when idle it´s time to pull the oil pan and clean the oil pump screen.

Advancer Points



Advancer Pick-ups

Dear scirocco. Thanks for the answer. That's right that 18T front sprocket needs more torque, but I just want to get the gearing closer to stock ratio. Let's see what it does - if the clutch can handle it.

The ignition advancer was stuck when I got the bike - because the side cover was cracked - and the advancer was rusted. I replaced it with the one from the donor bike, that one was just fine. I tryed the movement of the arms and it did move well when I installed it. There was only one position that you can install it, I havent seen any adjusment posibillity there.

I also cleaned the oil pickup when renovating the bike and since then i have ridden maximum 1000km.

Tomorrow afternoon I will go for a ride and I'll make a video for you, to hear the rpms when accelerating etc. It might help you evaluate the situation.

One more information - my bike does have a terrible fuel economy, It uses about 7,5L/ 100km - (cca 33 mpg) which is almost a double of the OEM spec numbers. Which could be an indication of bad timing.

Thank you

To give you an idea about the gear/rev/speed Ratio you have to looking for on your next ride.

I know by experience that this definitely isn't my case - I reach 120 km/h on 6th gear with at least 10 000 rpm. So there is something really wrong with my bike.

According to the manual, the 1982 Kz550B3 uses 16T front and 40T rear. That is the same as the Kz550A model. The Gpz's had more power so to fully realize the top end, they changed the rear to 38T. The Kz550C Ltd had a smaller rear wheel so they increased the rear sprocket on that bike to 38T as well.

So you are really only off by one tooth, and that is on the rear, which should not make much noticeable difference. It changes the top speed at 9500 RPM from about 186 Kph to 181 Kph (for normal tire size).

Yes you are right - I checked the manual and it should be 40T. So it isn't due to a gearing issue.

Do you have any other idea what it could be ? We might know much more after I send the video.

Thank you loudhvx

Yes a better video might help.

If you remove the gauges from your bike and just ride it around that way, does the bike seem to have something wrong. In other words, is this problem only because you are looking at the gauge numbers?

The 550 B should have the same power band as the Kz550 A which I've ridden quite a bit. The 550 A engine lets you know its time to shift at 9500 rpm because it pretty much stops pulling there. If you ride it around and the engine wants to keep pulling hard past 9500 (and you feel the bike accelerating hard past 9500 in anygear) then I suspect the tach is not reading correctly.

You should get a precise outboard tach anyway for tuning, but in your case, it would show if your bike each is way off.