KZ750H Restoration

The guy I talked to from Dekra seemed to think we should be fine with a stationary test. Fingers crossed...

Went for a semi-decent test run today. Everything is running smoothly and man does that thing have some torque low down! Completely forgot what it was like riding it, when I opened up the throttle at about 2500 rpm it just smoothly rocketed away. Man I love this bike
I checked the figures and was surprised to see it has as much torque as the hornet (my daily commuter). The hornet has a very steep torque curve as well, only really gets going at about 8000 rpm and peak is at 10500. The KZ just feels so much better low down, can't wait to really test her out.

Idle is a smooth as silk after sorting out the float height and checking the tach calibration. Starts to get a but dodgy if I leave her sitting and she gets to hot. Guess that's a built in temperature gauge.

Riding around the block is making me a bit nuts! Ordered my number plate yesterday and it looks like I can get it tested a the start of June. Feel like a kid before Christmas.

I do have another question: I need to put the choke on to start, but then have to take it off almost straight away. If I don't it starts spluttering a bit and them blows smoke (I assume from excess fuel). Is it normal to only need the choke very briefly in summer, or am I more likely still running a bit rich? I don't want to pull the plugs again to check until I can get some riding done under normal conditions.

Here's another video of idle after sorting out the float levels, replacing the throttle shaft and vacuum syncing the carbs - it's a lot better now. The floats were way out before despite having checked them, not sure how I messed that one up.
I didn't want to rev it too much in the video as I had been annoying the neighbours for a while already. You can hear how the revs back off to about 1500-2000 rpm quickly when I let go of the throttle, and then return to idle about a second later (most noticeable at 0:28). Pretty sure this only happens when I've been running it on the stand for a bit and it gets too hot. Not sure what would cause this but unless anyone tells me otherwise I'll be ignoring it until after the break in period.



Interesting side note: in Germany you can choose your number plate for about €12. The first 1-3 letters at the top are set according to where you live (B for Berlin etc.), you can choose the following 1-2 letters and 2-3 digits (4 in total). I figured I'd go for KZ 80 being that Z 750 was taken. I then found out that 'KZ' is on the list of banned number plate combinations! Was a bit confused until I realised it's the German abbreviation for Konzentrationslager (concentration camp). Don't really want to be riding around with that on my bike :ohmy:
In the end I went with K 738 (Z 738 was taken).

calum wrote:
'KZ' is on the list of banned number plate combinations

Yes, the third Reich period. That´s the reasson why every Euro (German) KZ badge and licence plate are missing the letter "KZ" combo, so only "Z"or other letter combo is allowed. You will never get any doomed "SA", "SS", "KZ" letter combo on a badge or licence plate here in Germany.
So the question is, should i be scared about my licence plate or i am on the safe side???

Scirocco wrote:

calum wrote:
'KZ' is on the list of banned number plate combinations

Yes, the third Reich period. That´s the reasson why every Euro (German) KZ badge and licence plate are missing the letter "KZ" combo, so only "Z"or other letter combo is allowed. You will never get any doomed "SA", "SS", "KZ" letter combo on a badge or licence plate here in Germany.

Interesting tidbit, I always wondered why the European bikes were labeled with the “Z” letter only .

Sounds really nice. Looks as good as it sounds. Work to be proud of!

Forgot to reply about your Video. Your bike sounds great and you have nothing to worry about your idle rev!!! Do a 100 km break in drive first before you fiddeling around with the carb adjustments.

Idle speed sounds high. I'd set it down some.
Where are the pilot screws set? If they are less than 3 turns open I'd richen them up some. The idle is hanging a smig which indicates lean.

Nessism wrote: Idle speed sounds high. I'd set it down some.
Where are the pilot screws set? If they are less than 3 turns open I'd richen them up some. The idle is hanging a smig which indicates lean.

Thanks Ed, that was pretty much what I was thinking/hearing. I checked the idle today with the digital tach, it was about 1300. I attached the tach to the coil -ve instead of winding around the plug lead as I think the sheath was causing some problems last time (it seemed to be missing signals and the values jumped around a lot) - this gave me good stable rpm readings.

The idle screws are another matter, they are giving me a bit of grief They are at two turns out and that is pretty much the best I can get it. a quarter turn in is worse, as is a quarter turn out. Going 1/4 out causes it to return to idle smoothly, but a lot slower. At 2 1/2 it starts hanging badly.
Went for a short ride at 2 1/4 and it felt sluggish under 3000 rpm (was fine above). Checked the plugs afterwards and 3 and 4 were clean, 1 and 2 were as shown below.

I have a funny feeling that I either have a very slight vacuum leak (couldn't find any with wd-40) or one or more of the idle circuits is slightly blocked. All the idle screws were replaced, but three of them have 800km on them and one is new - shouldn't really make a difference, though. Headers are all about the same colour so I have been assuming that all cylinders are generating roughly the same amount of heat. I'll check the temperature next time I go round the block.

I decided to get a colortune plug so I can see what is going on. I don't think I'm going to have any luck with all the idle screws on the same setting and the colortune plug will show me if the idle mixture is correct. If it still hangs a bit then it must be a vacuum leak - or am I missing something?
Anyway, it is more than rideable so first stop is getting an appointment for the MOT. Then I can put a few miles on her before I start obsessing over this (as per Scirocco) .

Some more info that I forgot in the last post.
- At 2 1/4 turns out the idle mixture was still lean as I got some popping on hard deceleration.
- The bike still spits out a bit of grey smoke on cold starts. I'm thinking this may be the rings as they are pretty close to the service limit (gap is 0.50-0.60mm)

Just revisited the video, this time with the volume up. I hear what Nessism picked up. Both the higher idle but more important is the hanging idle. Another learning experience, and a tuning aid shared from the more experienced members. Thank you!

Mikaw wrote: Another learning experience, and a tuning aid shared from the more experienced members. Thank you!

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