1978 KZ400 B1 - Scramber to be

loudhvx wrote: Sacrifices made in the quest for knowledge. Glad you're ok!

Ha, ha, ha. True and thanks.

What I learned: you need to make sure that the clutch is fully disengaging when you pull in the clutch lever before attempting to do a plug chop. (luckily it was only in 2nd gear, I was wearing a helmet, it was on grass). I also learned that my clutch is not functioning as well as I thought even though I could take off from a stop fine and it switched through all the gears fine too. I tried adjusting it again and again and it is still not disengaging fully - if I put it in gear and pull in the clutch it does not roll freely. I went ahead and pulled the clutch cover and the clutch appeared to be sticky - sometimes only the outermost plate would move. So I pulled the plates and friction discs to wipe them down, remove any rust around the tabs and re-oil and re-install. I measured the springs and they are still within spec. I measured the friction plates and they are outside spec and right at the wear limit (0.106"). IIRC the bike has about 12K miles on it, I suspect the clutch parts are original. I ordered new friction discs (6) from KG Clutch Company for under $50 this morning. For the same price I could have bought NOS but 40 year old friction plates that have been sitting on a shelf kind of bother me.

After a second look the bike is fine after removing clumps of grass from everywhere you can imagine (even had a clump between the 2 carbs). The only real casualty was the original mirror which I was not going to use but had grown fond of over the last couple of weeks. The stem was bent in the spill.

Tuning will have to wait a week or so until the clutch parts arrive. I wonder if the new clutch will have any effect on the tuning. It did not feel like it was slipping but with the clutch that worn it may have been.

I spent some of my down time waiting for clutch parts to arrive adding the “required” hoop. My welding skills are still crappy but my grinding skills continue to get better

Looks good to me.

New clutch friction disks came in yesterday. Everything was reassembled and it works so much better than before.

It took me a couple of rides around the yard to get the nerve to wind it out a bit since it hurt me the last time I was on it. But once I got comfortable I resumed testing the main jets. I am up to the 250s now. The mid range is even better, I have no issues anywhere with it, it pulls and pulls all the way to 3/4 throttle. But I am still too lean at the top end. The 250s were the largest that I had, so I am going to have to order more. I think I'll order 260-300. I cannot imagine it needing to go beyond that.

I am actually quite surprised that it needs more than 250s. I run 30 pilots and 220 mains the VM30s on my 76. I guess because these carbs are VM28s it needs bigger jetting for basically the same engine. Plus as noted before some PO had previously done some port and polish work on these heads in the past so I suppose they flow a little better.

I was going the wrong way on the jets. I think the ignition issues I had with the loose ground wire to the ignitor when I tried the smaller jets made me think that the larger jets that I tried after fixing the loose ground felt better. I had moved up to 260s and I finally realized that the bike was just way too rich and the bogging at 3./4 to WOT was getting worse. I put back in the 180s and I am finally getting response from the engine at that 3/4 to full throttle range, it pulled and pulled. Whew, finally getting close! I was getting worried that there was something wrong with the timing, the advancer, etc.

The 180s are the lowest size that I have and the next size up that I do have is 200s and the bike did not like them. So I will have to make another trip to the local Kawasaki/Honda/Suzuki/Yamaha dealership, which surprisingly carries mikuni jets, to get 190s, 170s, 160s, 150s, 140s. I don't think I will get down that far but I might as well get them just in case.

I did a couple of other things in the mean time. I went ahead and cut off the tabs for mounting the side panels. I was thinking about keeping them in case I decided to put them back on, but with the high exhaust that this has now the left side one will not fit. And no reason to use one on the right and not on the left.

I also found and fixed a couple of misc loose nuts and bolts that I either missed before or had backed off.

Finally, when I took my spill a few weeks ago the housing for the right hand handlebar controls which also houses the throttle cable cracked where the throttle tightens into it. I tried to fix it with some epoxy twice but it has separated again and it leaves my throttle cable inoperable. I don't want to take a chance of this happening while riding so I am going to have to replace it. Unfortunately after taking a look at Ebay I do not see the same style that I had previously ordered. I will have to go with something similar but not exact. I only hope that the wiring is the same for the new one as the one I already have.

Thanks for the update.

I did do a preliminary startup on the 75 D2. I used 30 pilots and 140 mains. I was only running it to make sure the charging system was working since the previous owner sold it to us with the flywheel bolt sheared off and used epoxy to hold the flywheel on. The flywheel and starter clutch were being held in place by the starter chain! WTF! I really hate some previous owners.

Anyway its all back together and working now. The bike will not fully rev and the idle is very unstable. I still need to assess the coil's condition. We have some 120 mains to try next since it seems to take more throttle if we roll it on slowly.

Wow, luckily you found that flywheel issue!

Good luck with the carb tuning.

Gave the bike a bath and took a few pics yesterday evening.

After looking at these pics I am starting to pick it apart. :huh: :dry:

I'm not sure I like the number plate side covers, I may remove them.

I really wanted that smaller LED headlight to work, on paper I thought it was a good idea. In reality since it does not house any of the wiring then it is just bunched up around that area. And because it is small it does not hide any of that or the cables. Maybe some kind of plate/cowl like many tracker style bikes have will help clean up that area.

While the seat is very comfy it doesn't look great. I will eventually either have to sew up my own cover (been wanting to give that a try) or have it done professionally.

So the seat needed some work and it was suggested to me that a rack on the back would be the perfect addition to a scrambler. So I set about making a rack, shortening the seat to make room for the rack, adding additional upholstery foam to the seat to smooth out the bumps and putting it all back together. Additionally I had to replace the RH control because it was damaged in the spill I took a few weeks back.

The paint on the rack is a little too glossy right now but it is the same matte frame and roll bar paint that is on the rest of the frame so it should fade a little as it cures.











Now back to main jet tuning, but it is getting close to done. I left off with 180s and it ran much better than ever. I bought a pair of 190s to fill the gap between the 180s and 200s on hand. I also bought 170s, 160s and 150s. I think my next step is to ride with the 180s again and check the plugs since the last time I rode with them the throttle cable was a suggestion because of the RH control damage. Then I'll go down to 170s and see how that goes and proceed from there.

After I have the carb jetting dialed in I only have a few small tasks to do (like pull off the mild steel 2-1 collector and paint and wrap it since it is already showing signs of trying to rust) and it will be ready to get plated and get on the road. Then we'll see what happens after that. I'd love to keep both of these KZ400s as they really serve 2 different purposes but I'd like to move on to another bike/project of a larger cc KZ and I probably can't afford to do that without selling one of them. I think this one would bring a higher price than the other but who knows I may fall in love with this thing and not want to part with it.

Nice work on the rack addition.

I've made progress on the two Kz400's I'm working on, but I haven't gotten to the VM30 jetting yet. Just finished the battery box and will be rewiring this weekend. The stock 400 is running great . I added an igniter triggered by points and so far it works great. The bike runs much smoother with the igniter than the worn out points. No matter how much I cleaned and filed the old points, the pits were just too deep and the bike would hesitate after a few miles. Now it runs smooth for miles and miles using the same pitted points.

I'll post the details when I write them up. The upgrade only costs about $10 to $25 depending on where you get the module.

I'm currently using the electronic ignition from the later KZ400/440s but I've got the details bookmarked for the HEI ignition module should I ever need to replace them. It is definitely something I want to try.

Interested to hear what you're up to with this one.