Mikuni VM 33 Carbs

Jets are ready to go in.
Steve

Went back to the 132.5 main jets.
Steve

Too fat.
Steve

Doesn't pull as strong at WOT with the 130's in there. Gonna try going down on the pilots and put the 132.5's back in after 100 miles.
Steve

Now that's more like it.
Steve

Got my #35 pilots and will adjust the float levels while the carbs are off.
Steve

Got them all even. Now to RIDE THE PISS OUT OF IT. :woohoo:
Steve

What fuel do you run through those carbs, Steve?
The gas I use is Shell Regular E10. Mid-grade and Premium carbon up the plugs, so I stay away from it. That includes Ethanol-free 90 octane.
I know the time has come again for new rings, but she's running so good that I hate the idea of taking it down until riding season in 2018 is over. We have had mid-60 temps for a few days here in W. Michigan, and it sure has been nice riding weather... :silly:

Feels more responsive, starts easy and everything feels right. My RS34 carbs have 17.5 pilots, .7 air jets, 125 main jets, and center clip position on the needles.
I think I've finally figured it out, except for the float level thing. I believe this series carb is meant to have the fuel higher in the float chamber than others. After bending float tabs to an extreme angle to achieve lower float levels which didn't seem right, I decided to set them back to 18mm +/- per the Mikuni instructions rather than assume 3mm below the flange applied to these carbs...and that was a good many rides ago.

Pulled the plugs this evening and took a couple pics. Aside from the carbon on the outer ring, I think she's sitt'n pretty with the jetting.



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Figured I'd add another pic which partially shows the widened air box that is still going strong. I'm done with rubber air boots. The stacks open inside, just behind the RAM AIR filter media which seals them at the front, but permits air to flow into the box around the stacks as needed. Most of the air supply passes through the original intake opening beneath the seat, but the cover and snorkel are replaced with filter media over the hole. Way I figure, let the motor pull in whatever air it wants, through a well-filtered enclosure, which also serves to dispose of the engine fumes and oily vapors via the breather filtration system that was originally designed into it.
Maybe that is where my oil is disappearing to. :S




Air box interior as viewed from the back. No air filter media covers the stack openings inside the air box. but one 6" square piece is fit over the snorkel lid hole.

I'm using regular fuel. I'm going to pick up some #20's just to try.
Steve

Am I correct to think that starting with lean jets is better than working back from overly rich?

Would adding fuel by small incrementally greater steps produce better results that are easier to read on the spark plugs? Seems like once a good tune is established, then a simple up/down Air Jet change should be all that is needed to accommodate moderate humidity and air temperature changes.

:whistle:

daveo wrote: Am I correct to think that starting with lean jets is better than working back from overly rich?

Would adding fuel by small incrementally greater steps produce better results that are easier to read on the spark plugs? Seems like once a good tune is established, then a simple up/down Air Jet change should be all that is needed to accommodate moderate humidity and air temperature changes.

:whistle:

Normally that would be the case. These carbs were so munged up by the PO the only thing I could do was try to take them back to factory but then found they had 2.0 slides instead of 1.5's for the Kawasaki's. I had a choice of buying slides ($400) or make these work. At first when I discovered the emulsion tubes had been drilled and soldered them, it made a big difference but mileage was lousy. I'd go down on the pilots and get pinging when it got hot on takeoff. I tried to compensate with the needles then main jets. That's when I read about setting the mains first with the needles in the center slots so it would pick up at roll on without picking up more when I let off the throttle. Mains set. Meanwhile I've been going down on the pilots looking for that tan color. The best I could do was #50's but the mileage was still too low so I went with the #45's. That's when Zed 1015 suggested .6 air jets. That worked but my mileage dropped again when I went to .5's. I just put in #35's with 130 mains and it runs great but the mileage still isn't where it was a couple months ago when I had 127.5 mains. I'll be going back to the .6 air jets when I get back home. I suspect I can go down further judging by the air screws and plug color.
Looking at the manual the early Z1's had 2.0 slides and #20 pilots. The later 74-75 Z1's had 1.5 slides and 17.5 pilots. I may be able to go #20 pilots but I doubt I'll ever be able to use 17.5's
At least I've been able to do these things myself for little money spent and my time. I'll get there and it's a blast "RIDING THE PISS OUT OF IT" testing it out. :woohoo:
Steve

Steve, I know how difficult it is to struggle to make things work. Seems like those carbs have given you constant grief having the incorrect slide size for your engine.
Not sure what a good used set goes for, but I ran across four 1.5 VM33 slides for about $200 dollars, and may be able to get the price down lower than that.

Any interest in something like that?

:whistle: