VM26 Set Up Recommendations

I'm looking for jetting recommendations for VM26 carbs on my 79 1000 shaft.  I live at 900' and I believe engine is stock.  I'm running the stock airbox, a Delkevic 4 into 1 exhaust, green dyna coils and dynatek electronic ignition.  Carbs have 118 mains in it now.  What size would you guys start with using this setup?  Thanks!  

The dyna ignition, coils and Delkevic exhaust etc need no jetting changes.
You may only need to account for your elevation in which case lower than sea level means go larger mains from stock and higher means smaller mains than stock.
The current 118's are larger than stock and so larger than what you would require above sea level.
Your 79 ST should have vm28's not 26's but reverting to the 26's stock jetting should suffice..
 

Thanks!  I know 28s are original for this bike but I have early vm26s as confirmed by forum member Nessism who is rebuilding them.
I failed to mention that I am running a K&N filter inside the stock airbox, in case that matters.  It did run OK with the 118s but it would sometimes pop on quick deceleration.  These carbs had some other issues so maybe the 118s were put in there to mask other problems the carbs were having.
So stock setting recommendation for the 26s would be: 107.5 mains and 15 pilots.  Should i put in a main that is 1 or 2 steps richer?  Say 110 or 112.5 with the K&N?
Side note: I am considering taking this bike to CO for a 4 day ride at elevation.  I know it will run richer at elevation so I would like to avoid fouling plugs but I definitely don't want a four day ride to drive the decision of what will work best.  I can always rent a FI bike there or take spare plugs in case they foul.

You should keep the stock 26mm jetting and if the K&N flows significanly more than stock to cause off idle hasitiation you should fit air correctors and go up a size on the mains.

So, I'm the guy going through these carbs.

Code Z12 00

Specs:
26mm (VM26SS) KZ900A4 & A5 
 Main Jet  115 
 Air Jet  1.0 
 Needle Jet  O-6 
 Jet Needle  5DL31-3 (last number is the clip position) 
 Throttle valve (slide)  1.5mm cutaway 
 Pilot Jet   17.5 
 Air Screw setting  1 3/8 turns out 

Compared to most VM26's for the 1000 bikes, these carbs have much richer jetting.  
Mains for most of those carbs range from 102.5 to 107.5
Pilots range from 15 to 17.5

So, the question remains: what jetting?  
I found some 17.5 pilots and 115 mains, just like stock.  Bumping two steps may seem appropriate if the stock jetting was 105's, but these are at 115 stock.  

And why are the 900 carbs jetted so much richer than the 1000.  Is it because the bigger engine creates more vacuum, which pulls the fuel harder?  

Most jetting variences between models were simply to account for the different airbox and exhaust designs. the basic engines are all the same .
The later bikes had slightly more restrictive/baffled intakes and exhausts for noise and emissions etc which means that the smaller jetting kept the required A/F ratio in relation to the slightly lower intake volumes.
There are also subtle differences in the needle jet tubes air bleed holes which weakens or richens the atomised mix at the needle jet which also explains the requirements for different size needle jets, pilot jet sizes and slide cutaway that was all in persuit of refining and smoothing the transition between stages in the fueling curve over the years.
On all machines the stock jetting was sufficient to cover the requirements of all stock rebore oversizes without change so in practice the stock jetting works just fine on a stock 1000 which is really just a 900 on max oversize.  



 

Thanks guys!  I was looking at the posts in this thread  kzrider.com/forum/3-carburetor/618383-carb-opinion?start=24 and wondered if it applied to my setup.  But it sounds like, even with these 900 carbs, I should stick with 115 mains and 17.5 pilot....possibly going one size larger on the mains and air corrector jets if necessary.  The knowledge on this forum is amazing! 

Thread drift...

The floats in these carbs have a shinny coating on them.  Thought it was varnish, but acetone and carb spray won't touch it.  Scrapping with a fingernail can damage the coating, but it's not easy.  Anyone see this before?

Nessism wrote:

Thread drift...

The floats in these carbs have a shinny coating on them.  Thought it was varnish, but acetone and carb spray won't touch it.  Scrapping with a fingernail can damage the coating, but it's not easy.  Anyone see this before?

No! Never seen that on a stock float.
Definately on the right track with the varnish idea.
Looks like a PO's fix for porous floats.
Maybe something like a 2 part resin such as Araldite or similar  .

Thanks for the info.  I'm thinking...replace the floats.  I have spares.

I think the main reason why carbs ran much richer on earlier engines is because they run better that way, and as time progressed stricter environmental regs forced engine manufacturers to lean their engines out in order to meet emission requirements.