1979 KZ400 (And KZ440, now powered by Mikuni)

Re: 1979 KZ400

Thanks, yes, I know. I stare at my Gold Star every day waiting to ride it. Just finished a CB400F, working on my CB750, then a CB400F restoration. They will be sold in the spring and I can finish the Goldie.

Then I am going to molest my 75 KZ400. It was incomplete and rough looking so I do not feel bad modifying it. My goal is to make it a minimal, light weight, fast cafe racer with heavy British stylings. Should be fun, until then I will follow your build.

Re: 1979 KZ400

So I'm anxious to start tuning the Mikunis on the "new" 440 once it's running right (locked up timing advance and clutch )

I've been scouring the interwebz for carb resources and compiled a list here:

https://docs.google.com/spreadsheet/ccc?key=0AsuVgwYc9Ah3dHBtNGZXVFYzRVYyb3k2eklnR1A0SUE

This is a combination of information from this forum, armbell (KZ Twins forum), Dime City, and Sudco.

Veaone's entry is especially interesting to me as that's the exact engine/carb combination I'm planning on using.

Here's a screenshot in case I do something stupid like trash that spreadsheet:

Re: 1979 KZ400

I'm interested to see how you make out with the new carbs. After I bought my vm30's for the xs400 I thought about getting a set for the kz400 but never did. It runs pretty good with the stock carbs (jetted) so I just left it the way it is. I would like to see if you get some extra ponies out of the new carbs.

Re: 1979 KZ400

Millenium,

Yeah....I think I'm going to stick w/ the stock carbs on one of the KZ's...but the set I have for the 400 were really nasty as in corroding aluminum...no amount of cleaning will take care of that. They may run OK, but it would just always bother me every time I looked at it.

At the same time, another set of VM30's is a pretty minimal "investment" so both bikes can run carbs that share jets/gaskets/etc.

So we'll see....get the 32's running for now, since only the 440 runs right now anyway... just want it to be ready for spring

Re: 1979 KZ400

I love the spreadsheet, much better than the "MikunVM30_Notes.txt" file in my KZ400 folder - though I do have a couple of other cool pages of notes such as SwingarmSwapOptions.txt and FrontEndSwapOptions.txt

Looks like you have most of the same notes that I have, but it looks like I found two others if you'd care to add them:

Mikuni VM30 setup for CB 350/360 with K&N Filters and megaphone exhaust (Dime City's Scott Turner kit)
150 main jet, 3.0 slide, PO needle jet, 2.0 air, 50 pilot, and 6F4 needle

Recommendation for VM30 and CB350 from honda twins forum:
150 Main Jet, 2.5 Slide cutaway, 3d on Jet Needle 6F4, Needle Jet 159 P-5, 1.5 Idle screw, 2 Air Jet, 3.3 Fuel inlet valve, 20 Pilot, 22 Float Height

Re: 1979 KZ400

Yeah I know what ya mean about the carbs being ugly/corroded.. It took a lot of work to get mine to where I could stand to look at them....The biggest problem I have with my Vm's is getting the throttle response to be snappy from just above and idle. (the first 1/8th of the throttle) It feels kinda "flat" and stumbles. I thought it was jetting, but I have had several people tell me that it is because the vm's don't have any type of accelerator pump because they were meant to be on 2-strokes. I'm new to messing with these carbs so I couldn't really argue. Although I know a ton of 4-strokes that run the exact same carbs with no problem. I am looking forward to seeing how they work for you. I hope you figure it out so you can tell me what to do..haha

Re: 1979 KZ400

diggerdanh said:

I love the spreadsheet, much better than the "MikunVM30_Notes.txt" file in my KZ400 folder - though I do have a couple of other cool pages of notes such as SwingarmSwapOptions.txt and FrontEndSwapOptions.txt

Looks like you have most of the same notes that I have, but it looks like I found two others if you'd care to add them:

Mikuni VM30 setup for CB 350/360 with K&N Filters and megaphone exhaust (Dime City's Scott Turner kit)
150 main jet, 3.0 slide, PO needle jet, 2.0 air, 50 pilot, and 6F4 needle

Recommendation for VM30 and CB350 from honda twins forum:
150 Main Jet, 2.5 Slide cutaway, 3d on Jet Needle 6F4, Needle Jet 159 P-5, 1.5 Idle screw, 2 Air Jet, 3.3 Fuel inlet valve, 20 Pilot, 22 Float Height

Click to expand...

Thanks man, I'll add those tomorrow when I'm back at a PC...editing spreadsheets from a tablet sucks

What front and rear end swaps do you have worked out in those secret text files?

Re: 1979 KZ400

Updated the spreadsheet.

I think the starting point is going to be:

Pilots: 25, 35, 50
Mains: 150, 160, 170
Needle Jet: P-5 (the carbs I bought came with Q-6's....much richer than the P-X needles)

That should be enough to get the 440 running OK I think. Does anyone know if Dime City stocks the float bowl gaskets? I want to order all the jets and such from them, but I really need new gaskets and don't want to have to place 2 orders if I can help it.

Re: 1979 KZ400

So I have my rear sets sitting on the workbench. Having never mounted a set before, nor ridden a cafe with them, I'm not precisely sure how I want them positioned. I'm already a bit of a big guy for a little 400 frame, so I'm not sure if the normal "mount-them-to-the-passenger-mounts" solution is the best idea.

Fortunately, we have some talented and inventive members on the forum and last week I found this:



courtesy of Dyrden's Show and Shine thread here: http://www.dotheton.com/forum/index.php?topic=44671.0

I really liked the adjustable height, and sexy aluminum block. Since I am not sure how I want them, I'm going to create a "first version" bracket which will give me height and front to back adjustability. It won't be the prettiest, but it should be functional, and then once I ride the bike for a while, I can take the measurements and make something more permanant that looks better. Here's what I'm thinking of...forgive the crappy modeling and photoshopping





And mount it up similar to Dryden's method:

Re: 1979 KZ400

BLSully said:

What front and rear end swaps do you have worked out in those secret text files?

Click to expand...

Ha ha. No secrets, just pieces I've picked up from things others have reported in forums, some guesses from putting 2 and 2 together, but not a lot of things I know for certain. But basically some fairly easy front end swaps should be: EX250, EX500, GSXR650, GSXR750, R6 and R1 depending on whether you want traditional forks or USD forks. EX250 and EX500 swingarms should be easy swingarm swaps but will require welding shock mounts to the swingarm if you don't want to do a mono shock conversion. If you want an extended swingarm the ZL250 (Eliminator) swingarm is said to be "almost a direct bolt on" that is 29" between pivot pin to axle - about 10" longer than my stock swingarm.

Here is an unedited example:

Early (1998-2001) (YZF-R1) R1 USD forks front end are said to be a direct swap to RD400. RD400 said to be a direct swap to the KZ400... so early R1 (and R6?) forks and triple could be a direct swap to the KZ400. Probably any year R1 or R6 because the bearing sets are the same for all years.

KZ550 front end is a straight bolt on, but they are a little longer than KZ400 and even KZ440 stock and have a leading axle.

Suzuki RG(V?) 250 frontend is a direct bolt on with better brakes and suspension
XV250 Virago front end is a direct bolt on swap too. Maybe xv125 and xv535 too.

1996-1999 (maybe 2000-2003 too) gxr600 forks/triple should work too (non USD)
gsxr750 front end fits great but the stem is a little long, just needs a spacer
zx6r front wheel with the gsxr forks

94 Katana front end fits on well with the Katana stem. Ah, Katana = GSX so that makes sense

EX250 front end fits nicely but the stem is a little long. Spacer should work.
Same goes for the EX500.
EX250 and EX500 also both have 15mm front axles so should be able to use stock wheel with possibly custom spacers


EX250 Ninja swingarm will bolt right up. However EX250 used 16" wheels through 2007. 2008+ have 17" wheels. So there may be clearance issues with KZ400 18" wheel on earlier EX250 swingarms. Use the KZ400 bolt and bearings. If you use swingarm, wheels, brakes, etc. from the EX250 it is all an easy fit, sprockets line up, etc but you'll need a custom 520 front sprocket.
EX500 swingarm may be a little wider than the EX250 but it should fit with some tweaking. EX500 used 16" wheels through 1992, but 17" from 1993 on. But ninja swingarms were made for mono shock so shock mounts would need to be welded on or a mono shock conversion.

Kawasaki ZL250 Eliminator swingarm is said to be "almost a direct bolt-in", but its pivot pin to axle distance is about 29"

XT500 swingarm will fit but will also need shock mounts welded on

FZR400 and FZR600 swingarms might also be an option since they are a common swap onto the EX500.

GSXR750 swingarm may fit too with a little work, and I bet if those do then so the GSXR600.

KZ400 uses the same front and rear sprockets as the KZ440 and KZ750 twin

Dual front disc brakes by using lowers and discs from SR650

The main crank bearing shells are the same part as the GPZ900R


KZ400 Upper 30x48x14
Lower 30x48x14

30x48x14
30x52x17 EX250 (Ninja) 86-12, EX500 (Ninja) 87-09, KZ550 80-83, KZ650, KZ750 76-83, KZ900 76, Z1R 78-80, KZ1000 77-80

30x55x17
30x55x17 GSXR600 97-12, GSXR750 96-09 11-12, YZFR6 99-06, YZF-R1 99-06, SV650 03-06,
Triumph Daytona 675 06-10, Triumph Sprint ST 05-10, Triumph Tiger 07-10, Triumph Street Triple 08-10

KZ400 - 15mm front axle, GSX600/GSX750, EX250/500 are the same size.
KZ400 - 17mm rear axle

Re: 1979 KZ400

Thanks for sharing all the info. Ideas for my KZ400 are percolating ...

Re: 1979 KZ400

A new member on the Kawasaki Twins forum just posted this to my VM30s post on that site:

The bike is a 1975 KZ400D. I'm running Emgo Pod filters and some aftermarket straight through mufflers on a dual exhaust system. Everything else is stock.

Best results for me were:
Main Jet: #230,
pilot jet: VM22/210 #25,
Throttle valve cutaway (slide): 3.0
jet needle: #6F5 on #4, (STOCK Needle, 1 Clip Richer)
Air Screw: 1.5 turns out
needle jet: #159 P-5, (STOCK)
air jet: BS30/97 2.0, (STOCK)
needle valve set: VM34/39 3.3, (STOCK)
float height: 22-24mm (STOCK)


As they come stock, the carbs were a little too rich on top and way too rich on the bottom end.

I did all the jetting with an air temperature of about 35F, so in the summer a couple of tweaks may be needed.

I started with 190 Mains and worked my way up until it would take full throttle without gasping for fuel. 230 worked well. The bottom was so rich with the #40 pilots it did not want to run cleanly at all. With the stock 2.5 slides in, I finally went all the way down to #22.5 pilots to get it to pull well on the bottom right off idle. There was still an off-idle "burble" when just cracking the throttle from a steady slow speed cruise, so I put in the leaner 3.0 slides. With this change, I went one step richer on the pilots to #25 so at idle, the mix seems good and just off idle that "burble" is gone. The new slide also leaned out the mid-range, so I raised the Jet Needle 1 notch to Position #4.

If you can live with that small "burble", you can set these carbs up to work about 90% well with just the #230 mains and the #22.5 or #25 Pilots. Even with just those two changes, it worked maybe 50X better than the CV carbs.

Re: 1979 KZ400

OK, it's started warming up in IL and I've gotten back in the garage to work on the KZ440. I think the 400 is going to take another winter....

I cleaned my VM32's and put them on the 440 to see how rough it would be to get it running. Surprisingly....not hard! It took a bit to get it to start as I think I flooded it at first : but after it fired up, my bench sync proved to be nearly spot on. It was idling pretty high, but would run smoothly without the "enrichment" circuit on. I moved the idle down to a more reasonable level and started tweaking the idle air screws...right now I'm somewhere between 1.5 and 1.75 turns out, and while I don't have a tach cable, I'd estimate the RPMs are in the 900-1100 range....not bad considering I basically just threw them on there with my "best guess" of parts.

Speaking of parts:

#170 mains
#35 pilot
2.0 air jet
3.0 slide
P-6 159 series needle jet
6F5 needles, middle clip

So, it idles nicely, and it'll cruise low-rpm (like, maybe under 3k, definitely under 1/8th throttle) pretty nicely. I've run it up through 4th gear and it does OK steady state with a smooth (and small) roll on the throttle. Potentially you're seeing where this is going?

So, I basically cannot get it to run with > 1/8th throttle without VERY gently rolling on. Just dies. Doesn't really burble, just coughs, gasps, and quits. If I come off the throttle fast enough, it'll pick up it's nice smooth idle again, and with small, smooth movement, it'll get to ~1/4 throttle (in neutral...so... not saying much) and it's spinning pretty well. It does sound smooth when I do it like this...no coughing or stuttering. It's only when I crack the throttle hard that it chokes.

Alright, since I figured this would be a lot easier to hear and see than explain, here's a video I took. This is with the motor "pretty" warm... I rode it around the block 3 times and let it idle for about 5 minutes to do a plug chop.

http://www.youtube.com/watch?v=ApvFCyT2mmA

If it helps at all, here's another video (taken the day before). I was chasing down the hanging high idle which /seems/ to have been fixed by tuning the Idle Air screws....it still has a tiny hang when it's warm...when cold, comes RIGHT down to a nice idle....does that tell you anything?

http://www.youtube.com/watch?v=VJ8EFaQwA3A

You lifted the "choke" so that suggests it's too lean at idle. Maybe an air leak and if not try larger pilot jets.

Snapping the throttle open will kill it even if teh jetting was perfect. Those carbs are pretty big and at low engine speed, gas velocity through the carbs is low. Snap the throttle open and it just pulls in air and dies. Richen the bottom end up will improve that a little.

You may find it prefers a 2.5 slide to richen that off idle range

Thanks for the input Teazer.

The carb boots have definitely seen better days! (Un?)fortunately, spraying WD40 (it's what I had next to me) all over the boots did not change the idle at all. They do, at least for the moment, seem to be sealing properly.

Going with the theory it's lean when I crack the throttle, would altering the needle be create sufficient change to determine the direction I need to go? Obviously I understand it may will require further jetting/needle changes, but, in other words, at the throttle position I'm currently having trouble with (1/8 - 1/4), will the needle height have enough affect to at least give me an indication of which side of stoich I am on?

I also have a set of Q-6 needle jets (they came with the carbs). Maybe will try throwing those in and seeing what effect that has.

Honestly the biggest difficulty so far lies in the fact I live in a subdivision of townhouses, so "opening it up" around my house is not really possible without the friendly red-and-blue showing up after a few pulls

Well, I ordered a set of 2.0 slides, a couple other pilot jet sizes, and needles (6F4's).

Hopefully that's not /too/ much of a change from the 3.0 and i end up pig rich, but I'd have hated to order the 2.5's and still be lean. Like Teazer said, the air velocity through the big 32mm bores is lower so hopefully the 2.0 slide will help balance that a bit on the low throttle openings. Will update after the IL spring rains abate and I can get the bike out again.

Sounds like a plan. I was planning to take a bike up to Union Grove this week and all week was rained off. The country is suffering from record drought and all we're getting is rain. My garden loves it, but we need some breaks in the rain to ride.

Off Topic: Teazer.... Union Grove, IL?

On topic: Even though it's 42 degrees, windy, and wet, I couldn't help but play with the carbs on the 440 today. I haven't gotten my order of new parts yet, but using the parts listed in my post above w/ the 2 videos I tweaked some things....

* Moved the e-clip down one notch to richen up the needle
* Reset idle to around 1200-1400 rpm and took my time listening to the motor as I adjusted the idle air screws to find the peak rpm, then reset idle to ~900.

I must have gotten it closer this time as it will actually idle much lower now....feels like it's barely turning....maybe 600-700rpm but won't stay running very long. It'll tick along all day though where I did set it.

After doing this, I took it out in the neighborhood and ran it up and down the street a couple times. It's /really/ snappy right off idle now...still doesn't like to be cracked open hard, but pulls VERY well with zero hesitation coming off idle with maybe up to 1/8 throttle.

Once it's moving, I can SLOWLY pull it through the 1/8-1/2 range (very flat and coughy...guessing the slide is letting it lean out too much here?) and once it's up around 5000rpm or so (again, guessing, no tach drive cable) I can give it full throttle and it'll pull OK...not /hard/ but acceptably for the time being. I also didn't wind it out fully as I don't feel like being "that guy" in my neighborhood, but I do think it's safe to say it's lean in the midrange. Tomorrow is supposed to be nicer, though still cool (mid 40's) so maybe I'll pull the needles all the way up and see if that's a further improvement....or maybe throw the Q6 N/J in.

I wish the carb boots had vacuum ports so I could have that peace of mind that the carbs really /are/ in sync... doing it by ear is somewhat challenging since I don't have a ton of experience at this in the first place

How about adding these 5mm vacuum tuning ports from DCC

http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-carburetor-parts-5mm-vacuum-intake-tuning-port-adaptors-dcc-08-0013-2.html

More tuning today... Still cold but I decided I just had to keep working on it regardless.

Needles (6F5) at full rich clip with the P6 N/J was even better... Still nothing in the midrange though. However, it now makes (better) power up through about 1/3 throttle.

Just for kicks I put the Q6 needle jets in and put the needles back to middle position. Even more power and while the midrange is still flat, things are going in the right direction for sure. Can't wait for my 2.0 slides to get here. I really feel like that is the key at this point. Especially since it will run through the mid throttle positions as long as the roll on its slow.

One thing I noticed is the idle seemed to suffer as I pulled the needles up... Maybe they start flowing some fuel even at idle? As soon as I went to the Q6 needle jet and middle clip on the needle the next time I started it idled much better. Didn't entirely make sense to me but that is what I observed.

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