Hah!  Yes, those sure do look like vacuum ports!  I do stand corrected as Mikuni must have updated the design somewhere between the late 1990's and now.  I wish that I had that feature on my set of RS34's; especially when I was running them on the street.  

And, to answer your original question - synching your carbs with a good set of vacuum gauges can have a noticeable positive effect on your off idle throttle response, i.e. when pulling away from a dead stop.  If you're happy right now with how things stand, then no need to mess with carbs.  Maybe down the road if you really want to fine tune things.  Just my opinion.

Mike

And thank-you for You're inquiry, just checked my inventory and realized i was down to only 3 left! Just ordered more. Believe me this a surperior functionional item and waay cheaper then OEM, gotta think outside the box sometimes in a while for efficacy. And Thank-You for Your script thru the years on the VJMC rag, surprised they even have "printed" paper stuff anymore, Ha. If YOU need a sampling of what i'm referring to i'll send you a couple, check them out, fall in love with this concept and your on Your own.

An alternative to OEM that works everytime, have been using them for years. Find a supplier that sells the "bonded" washer for 10mm. I've tried the thinner Yamaha versions, read more pressure over a smaller surface area, but if You have any surface imperfections in either the banjo or splitter/caliper/master even those will weep. I buy in bulk here locally from Tompkins Industries. They outwardly will suffice as a suitable replacement but because of the nature of the bonded rubber internals, You won't have to ham-fist the banjo for a proper seal.

Got it, thank you Wookie !

Copper washers are the way. to go.
You can even stack them like I had to so the  rigid brake fittings cleared my custom triple trees.
They don't leak at all , before that gets asked..

Plain copper, I buy them from this source along with other things like their 6mm small head screws. I like them better than the aluminum washers as they seal better with less torque
belmetric.com/washers/solid-copper-gaskets/

Dragbike_Mike wrote:

The RS34's are great carbs.  Synchronizing them with a vacuum gauge or manometer can be problematic as the carbs themselves do not have any type of vacuum port on them.  And, if using J-model carb boots to mount the carbs to an earlier KZ head, then those boots won't have any vacuum ports, either.  I always confirmed that the slide heights were the same using a piece of drill rod.  Not as accurate as the vacuum gauge method, for sure, but good enough for a race motor.  It at least will get you in the ballpark.

Mike




 

Hi Mike
But the carburetors I have include some rubber plugs. Aren't they for connecting the vacuum gauge? 
 

I always use plain copper washers and anneal them before use as even new ones are work hardened from the stamping process.
The plated ones are pointless as the annealing removes it anyway.

SWest wrote:

If it's like the early motors you have to be sure all the m6 bolts are out top and bottom. On the early motors there are two threaded holes to be used to pry the cases apart. If one bolt is missed you'll hear that dreaded CRACK and the case will be ruined. So the answer is yes but be CAREFUL. 

Steve 
 

Yes, I've heard of that nasty crack to be avoided at ALL costs.
Will consult my handy old FSM, and anticipate some great advice for safe and effective crank extraction before the first bolt snaps loose...in forty years that is.

Still deliberating since I don't expect to race with the motor, and someone else may want it for that purpose.  Once installed tho, those thoughts will be over.
Besides, a beautiful crank is already in there, and I can leave the factory assembly alone to use it.

I used Goodridge 10mm copper crush washers last spring when I replaced brake ines. # 445-16-6 pk6 in  the drag spec Fatbook. They seem to work just fine. So far so good. Local bike shop has them in about week. No shipping charge as they are usually getting other stuff also.