PWK28s for RZ

[m in sc]

we got Josh's rz running with those exact carbs, it ran great as far as fueling went. 

[2steve]

The VM28s seem to have lost a little of the mid-range punch. I'm guessing it's a drop in velocity compared to the stock VM26 carb, but the top end would make up for that.

Maybe PWK28s will give me both.

[m in sc]

its not tuned for an rz, but your 400. different pipes, porting  etc. I ran 30s on my rz it had plenty of midrange,  but I tuned the carbs for that bike. you did a parts swap, w no real adjustment for motor difference . tbh im surprised it runs as well as it does just swapping it over. 

[pdxjim]

We run VM30's on the RD350 race bike we campaign in the 6hr kart track endurance race we do every year.

GRA2strokes Garrett tuned the topend (porting, o-ring skimmed heads, etc) and it runs stronger than any other RD I've ridden. Especially in the midrange which is everything on a short kart track.

[2steve]

PWK28's arrived today.
What about that orificed "power jet"?
Is that a vacuum port in the photo?
Don't know that I can trust the jetting "for Banshee with open intake" since the numbers on the main jets look too small.
Maybe the needle is right, but I don't see "JJH" anywhere on either the installed one or the extra.

They do look very well made

Do I need to check the float level?
Suggestion for oil injection fittings for drill and press into the carb boss?

[m in sc]

look at my pwk thread. I also told you some recommendations on setup.  those are bowl vents. they can just be left open. there is no vacuum port on them.

[m in sc]

https://www.2strokeworld.net/forum/index.php?topic=6585.30

leave the jet up top alone. Josh ran the carbs in my thread, the exact ones, on his rz (until he converted it to a 421). Jjh needle, I think he was at 152 mains and a 38 pilot and it ran strong.  it's good starting point that's been proven. look close you can just see them here

[2steve]

Thanks! Looks like UNI's in there. Right one might have to be 15° (battery box) and the left one straight. You used 30mm carbs though, right?
28mm would likely use the same main jet?

I'm looking to add vacuum for possible future use.
Will look to find an M5 or 10-32 "T" fitting. One branch for oil and the other capped off for vacuum. What could possibly go wrong.

These carbs are like jewelry compared to Mikuni VMs. AI told me that the default N68N needle is equivalent to JJH.

DID you adjust floats - or just check to make sure they were even?

[m in sc]

why vacuum? no need. seriously. the vac petcocks are just waiting to hydrolock your motor.  but if you must  can always drill and tap. yes jetting will be very close to that. same body. jjh needles available from jetsrus

[2steve]

I do have a brand new Yamaha RZ petcock and having had a Kawi ZRX with a vacuum petcock, I learned that the key is that tiny o-ring inside. A member of the forum sells them for cheap. Buy a bag of those (in Viton, I think) and periodically change them. So, seriously thinking about it.

RD400 barbed oil fittings and jets are on order for now. Planning to drill the carb boss so that they are a "press fit".

I did leave the RD400 petcock open once and it sat for a long time. Must have come really close to ruining the bottom end when I thoughtlessly tried to start it.

[m in sc]

not going to save it from leaking with a flake of rust behind it.. seen  that, hydrolcked a kawasaki concours motor that way. well, my ex father in law. also saw an h1 crank seal get blown out with a hydrolocked case, petcock again.(my friend mark in Alabama's 73)  new bikes.. ok. old stuff I never use vacuum. but again, my preference. even my tzr,  lined tank w vacuum petcock, has a manual valve after it. fwiw, im getting my pwks back Sunday,  i can look at where the jetting is for the rz and relay it. 0.02

[2steve]

And there's the perfect solution, Mark. Factory vacuum petcock with a manual valve after it.

I could easily put it on reserve while rolling along 

Relaying the jetting will be most valuable.

[1976RD400C]

My RZ vacuum petcock got switched to a RD400 type after sitting all winter and I was doing a spring start up. Thank goodness I wheeled it out of the garage. She fired right up. I look behind me and gas was blasting out of the exhaust pipe like a garden hose. Horrified, I shut it down. Somehow the one pipe must have had about a quart of gas in it. If I was in the garage, and it lit off, who knows, I may have lost everything. 

[2steve]

You would have lost some hair, at least.
When it happened to me, I went for a quick romp around the neighborhood to clear it out. It did run very well at that time.

[Kawtriplefreak]

I recommend an RD400 petcock for a stock or mild motor. And the 660 Raptor for a bigger motor with big carbs.