I am testing 3 carbs.

Carb1:  VM30SS, Jets: 180/50, 241 series needle jet (~42.7mm overall length, stock), 5EJ8 jet needle, position 3, tang at ~17mm.  OD Airbox 43mm, OD engine, 40mm.  Air screw 1&1/2 turns out, 3.0 slide

Carb2:  VM30SS, Jets: From Keyster rebuild (180/50), Keyster jet and needle, position 3, tang at ~17mm.  The needle jet at least "looks" the same but I can not see much internal.  The slow jet is keyster also.  The keyster needle measures very close to what a stocker is at different points and "appears" the same taper at least to my glass focused eyesight.  Air screw 1&1/2 turns out, 3.0 slide.

Carb3:  VM32-33, Jets: 180/50, 159 series needle jet(~48.5mm overall length via docs) and 6DP1 jet needle.   OD Airbox 58mm, OD engine ~40mm.  Air screw 1&1/2 turns out, 2nd needle position, 3.0 slide.  main jet access from bottom.

First, all 3 carbs fit the engine boot. Carb1 and 2 were ultrasonic cleaned, but still need to do #3.  The VM30SS has a threaded connection to cable, slip in to cap w/eclip, but the VM32-33 comes with a cable inserted connection w/screw in cap.   So, I drilled the cap out on the VM32-33 to around 6.90mm and put the #2 VM30SS cable guide on it w/E-clip.  I used a 6.5mm bit to do this, though I think 6.90mm bits are avail, then carefully smoothed out things w/2000 grit sandpaper. 

The VM32 is larger carb.  The air screw is on exhaust side, though easily accessible.  Running stock oiled air filter for carb1 and 2.  Carb3 had no element for test.  Yes, things will change when added.

So far...all 3 carbs have excellent idle and start characteristics.  Part throttle goes to the VM32.  The VM32 offers a much smoother and powerful throttle response all the way through the power curve.  I've went up and down the needle positions to find the best one.   As you would expect with a larger intake, the power hit is about 500-1000rpm higher, also offering increased power through the rpm range and smoother accel.

Top end.  Jets and Testing needed.  carb1 and 2 work on top end, but I suspect could use a little richer jetting based on plug.  Ground strap does not show a mark yet, so once fuel is adjusted, I can play w/advance a LITTLE.  less = better for this engine I suspect!  Going to test soon.
carb3, fail on top end.  As soon as it gets on main, it goes flat.  This carb comes stock with a 200 main but there is a 180 in it.  I need to up jetting on both carbs for top end testing and report back.

Any recommendations on how to adapt VM32 to the carb boot?  Stock air box boot is 43mm.  VM32 is 58mm.

Preliminary Summary:  VM32 is a good carb for this bike AND lots parts available.  I was pleasantly surprised the keyster kit worked well w/VM30SS.  
 
More to come!


VM30SS


VM32-33

 

Gosh you've been busy. Thanks for posting. I shouldn't even ask but is exhaust clean & air filter good. Look forward to more results. Don't think anyone's done testing quite like that before that I can recal reading.

I’ll be curious once you get them close, what’s the temp on the head. Will the bigger carb pull a bit more fuel and keep it cooler?

I wonder if the VM30SS would benefit from a different needle.  Yamaha, at the time, certainly did a great job on the bike, but with all the carbs avail now, seems like time to experiment. I would love to have a VM30-33.  Goal is NOT high end hp but I want it fueled properly.  Less heat certainly a benefit.

 

I love what you're doing.  Especially great trying "available" carbs and getting them jetted so someone has a starting point if they can't find an OEM carb.

That said, the "butt dyno" is not reliable.  Boyesen reeds are a good example.  They give a neat boost to off-idle throttle response and most people will claim they give you more power.  But they tend to KILL power on every engine except one I've ever tried them on.  "Feels" faster but performance is actually slower.

Larger carbs also give a more "responsive" feel at lower throttle settings.  I'm pretty sure this is due to the throttle opening getting larger quicker as the slide lifts the same amount as it did before...  so more of a "quick throttle" effect than actual power improvement.  

Dialing in the jetting for each carb and then using a dyno or careful measured acceleration testing is time consuming and tedious.  But the only way to find out which is "better".

The thing is, often "which is better" is not as important as having an option when say an OEM carb can't be found.  

Keep up the good work!  

I have a 32mm EI carb on one 360 motor. Everything controlled by the needle. No jetting whatsoever. That'd have you head scratching if not familiar with them. They supply different needled with varying tapers & just raise or lower by screwing the center spring loaded cable thingy with a special tool.

The needle jet on left from a VM32-33, series 159, Q-6, 6DP17 jet needle. The one on the right is stock,
series (241 or 247 hard to read), O-8, 5EJ8 jet needle. The stock VM30SS looks like a 241, but there is no listing for a 241, only a 247, which btw doesn't look like this one.

The 159 NJ w/6DP17 needle works in the VM30SS carb. I have it idling great and its quite smooth on accel.
Waiting on jetting today to play with WOT. Its 99F outside!  Might have to hold off till cooler.  This just opens the door to new parts for the VM30SS.
Yes, the NJ sticks out a little in the small body carb. The base is still sealed in body and ports on NJs mostly align.

Series 159 and 241 needle jets


VM30SS


VM32-33



VM30SS body w/stock needle jet


VM30SS body w/159 needle jet from big body VM32-33 carb

This is an excellent thread and I appreciate the work you are putting into this. I have rebuilt a 360A and am using a good carb from a '75 DT400C, which seems to be working ok. I do not ride it enough to say that it is perfect but overall performance is about what I remember from the time period.

I too have a sleeper pipe so will be following along as you go!!

Well done! 

Hi, nice to know the VM32SS works. Just another option for the 360A. I've got jets coming to fully test my VM32-33. Have not arrived yet.

Meanwhile, have clamped on a VM30-83 using cap from VM32-33 I modified. Comes with 40/250 jetting. You may think, no way w/those jets...but not so fast. This carb has performed really well. I did a brief roll on WOT and the mixture sounded good.

Later today will warm it up, then do some WOT run and chops to check plugs for mix and advance.

VM30-83 w/58mm Pancake Filter.

It doesn't surprise me that it ran pretty good out of the box, most "universal" carbs do.

Please avoid the trap of "the stock carb has a 180 main" and using that to use a 180 in the new carb... unless it's the exact same size carb and you're using the same needle and needle jet and everything else same sizes as stock.. 

Venturi size, needle, and needle jet differences often make a drastic difference in what jets are needed... especially the main jet.