Float Height 26ss Mikunis

What's the unapproved USD float height, 78 kz1000

Carb specs per FSM

1978 KZ1000-A2
Mikuni
VM22SS
105R Main Jet
0-5/2 Needle Jet
5DL31-3 Jet Needle (-3 means 3rd clip)
15 Pilot Jet
1.0 +/- 1/8 Pilot Screw
1.5 Throttle Valve Cutaway
32 +/- 1 mm Design Fuel Level
3 +/- 1 mm Service Fuel Level

What is USD?

Good Luck!

USD - UpSideDown
I cleaned and rebuilt the carbs and reset the floats to 25-26mm (that was the lowest one, they were all different). However, now it's really hard to start, have to crank a really long time to get fire and then very lightly ease into the throttle until it gets to the usual fast idle choke. Once the engine gets somewhat warmed up it starts instantly. The 32mm design level mentioned above seems waaay low as I'm thinking 25-26mm is too low and gas is having a hard time being drawn up. I'm planning on pulling the carbs this aft and thought I'd reset the floats dry then do the wet(service fuel level)of 3mm.

BTW the carbs originally had 15 pilots and 105 mains and I switched to 17 pilots and 107.5 mains as I had pulled the snorkel off the air cleaner and now this winter installed a fully baffled kerker. I reinstalled the snorkel the other day because like last summer the engine was a little boggy in lower rpm. I thought the 17 pilots would help but made no difference. I also have the pilot screw out 1 turn (couldn't they have put those screws in a better place?)The weather has been cold windy rainy and haven't had a lot of opportunity ride and experiment, just trying to get the basics set up, then get into tweaking. Thanks, Pat

Since your floats have had to endure 30 years of amateur bending (mostly bent inappropriately) they have lost their orientation that made the float height method of adjustment relevant. Suggest you try the service fuel level method to achieve an accurate amount of fuel in the bowl.

The "clear plastic tube test" may be done while the carbs are on the bike and with no disassembly required (other than removing the float bowl drain screw). And may also be done with carbs on the bench (holding them level of course).

During the float tang adjustment process, it's okay and faster to use only one float bowl screw when checking the level between adjustments. (This tip courtesy of wg)

As known, small adjustments make large differences, so go with tiny increments.

Good Luck!

Carbs on the engine was hard enough on my 750 twin doing the service fuel level. I can only imagine trying to do the two inboard carbs on the 1000 and still maintain what's left of my sanity:blink: . I saved my old manifolds for the 1000 and read about a tip here;) to screw them to a board and slip the carbs on, level it up so it's easier to adjust service fuel level on the bench. Thanks for the advice and I hope this helps my cold starting, it runs great otherwise. Pat

Have never used the clear tube test on a 750 twin, but using it on the large fours is cake.

And it may take longer to read this post than to actually do the test. :laugh:

Here's the clear plastic tube test to best check real-world float bowl service fuel level.
Quick and easy -- no disassembly required.
May perform test with carbs on or off bike.
Carbs must remain still and level during the test.
Do each carb separately, one at the time.

Turn petcock off.
Fuel line remains attached to carbs.
Remove side-located drain-screw from float bowl.
(May use a shop rag to catch and soak up outcoming fuel.)
Use short length of clear plastic tube.
Size of clear tube should match drain-screw hole.
Twist-thread clear plastic tube into drain-screw hole.
Rumor has it some folks prefer using a small plastic barb-style connector fitted into the drain-screw hole with the clear tube attached to the connector.

Hold clear tube against top edge of float bowl.
Keep it steady - don't let it move.
Turn petcock on.
Watch level fill and rise up in clear tube as fuel fills float bowl.
Fuel level visible in tube matches fuel level inside float bowl.
Slight fuel leakage from the drain-screw hole is immaterial and won't invalidate the test.
Repeat test to double-check result.

Smoothbore carb has larger bottom-located drain-screw hole. I use a tapered rubber grommet pressed or twist-threaded inside the drain-screw hole with the clear plastic tube fitted snugly inside the grommet.

Here is the special tool sometimes used for fitment into side-located drain-screw holes. It is a relatively expensive thumb-screw affair with clear tube attached that threads into the drain-screw hole.



With CV style carbs having combined function bottom-located nipple for both over-flow and drain, just attach the clear plastic tube to the bottom located nipple.
This does not apply to carbs having separate independent drain-screws and overflow nipples.

Refer to manual for specs as to ideal height of service fuel level. Usually, the correct level is slightly below the float bowl gasket, say 1/8 inch or 2-4 mm.

Float height is a critical factor for proper carb function, and once set, should last a very long time without needing any re-adjustment. Actually, the "testing" is usually much easier and quicker than the "adjustment" of the float tangs.

Good Luck!

Well, I got to my carbs yesterday afternoon and as you may recall I had set the design fuel level to 25-26mm. I bought a 3/16" nylon barb splicer ($1) and 2' of clear 1/4" OD tubing ($.10). I cut off one end of the nylon splicer to attach about 8" of the tubing and was able to "screw" in the barbed end into where the drain screw was located. Had an old lawn mower tank w/ shutoff, screwed 2 of my old manifolds to a 1x8 and screwed that to the front of my workbench. I then attached my carbs(used clamps on the manifolds so they wouldn't fall out and stayed level) to this setup, now everything level with proper lighting(old eyes ya know) and easy access to everything. Attached the tank to 2 carbs at a time (in-line filter also used, I worked too hard to clean the carbs to not use filter). Checked the Service Fuel Level on all four carbs and low and behold they were all 2-3mm!!!!Awsome!!!But why won't my bike start easily, crank forever to get some life? Well as I was reinstalling the carbs I noticed that the screw(the one that has a spring and nylon piece) for the choke(enrichener:P WG)was a little loose, tightened that down, charged the battery. I then gave the starter about a 1 second burst -no start- proceeded to give the next burst - INSTANT START!!!!!!!!
Why did I write all this? When starting these bikes you got one hand on the clutch and one on the starter(no hands left for the choke), I didn't notice that the choke lever was being pulled down a bit from the vacuum from starting. My bike needs FULL choke to start when cold. Choke lever stays where you put when the screw is tightened down properly. Plus I wanted others to know that other than carb removal and reinstall(with pods it's got to be waaay easier)which isn't too bad when the rubbers are still pliable this bench Service Fuel Level check is easy,out in the open and more accurate than trying to do it the cramped confines of the engine bay.
Thanks for the help guys!!! Pat