Wiseco 615 Big Bore Kit

For those of you that stuck with the stock CVK carbs, how many jet sizes did you go up? I think mine is probably running lean. I already have a Factory Pro Stage 1 jetting kit, I’m just looking for some guidance about where to start with it. 

Also, while I know that installing pod filters is a popular way to increase airflow, I want to keep my airbox. But should I think about modifying for more flow? If so, does anyone have any idea where to start with that? I assume drilling a hole or two in it somewhere like the EX-500 guys do all the time. But maybe just a K&N filter is enough? 

On the my GPZ550, I’m not running pods, I have in the past and I’m not a big fan, but sometimes you have to.   I have a K&N replacement filter and stock air box, unmodified.   I have heard of a mod you can do to it that makes it flow better but I don’t know what that is.  

Here’s a list of things I’ve changed in various combinations; it initially was leaning out on the mains and would not rev off full choke:

Changed main need jets (mains) from stock 94 all the way to 118, in steps.

Changed the air bleed from zero to 2.5 out.

Changed the needle height up, down,sideways…

Changed the needles them selves with some from various kits I’ve used over the past (why you should never chuck old carb stuff)

Modified the needles changing the taper 

Setting the float bowl up down, and finally wound up using Kawasaki’s recommended method of using the vent over flow tube method which worked perfectly. 

And of course total rebuild of it with new parts.  

And finally, last night I it pretty close, revs instantly, starts and idles.  It is however too rich, and I need to fine tune it further.     

What got it to this point, changed the needles to a set from DynoJet, then cut them by 4mm, went to 98 mains and 3/4 out on the bleeds.

577nitro

One thing I've learned in my Googling adventures is often times when you increase bore size or compression you actually want to jet down rather than up.  This is because the increased vacuum can pull relatively more fuel than before the mods.  I was running way too rich with my factory pro stage 1 kit (110/112 mains). I've gone down to 102/105 mains and it still may be running rich. I was getting 20mpg on the 112 mains. Now it's maybe 30mpg.  I might go down further, or just ride it out for a while until the rings are broken in enough to put the bike on a dyno. 

That’s an interesting aspect to think about  Zaddict, thanks. More vacuum must certainly mean more fuel entering the combustion chamber, but then wouldn’t it also mean more air? It’s always a mix of the two. I would suppose that while more fuel is being pulled in, a disproportionately larger amount of air would enter, just by virtue of the fact that air is lighter weight than fuel. Thus necessitating a jet that allows more fuel flow-through. 

Stock jetting tends to be pretty lean as it is. I’ve heard if you can’t get it perfect, that slightly rich is better than any amount lean, as the engine will run cooler. But maybe I’ve been hanging out with the wrong crowd, lol. 

Stereordinary wrote:

More vacuum must certainly mean more fuel entering the combustion chamber, but then wouldn’t it also mean more air? 

Yes, more air but it's the ratio that matters and it can pull relatively more or less fuel depending.  This is one of the more interesting explanations of the phenomenon I found on another forum - 

 "Venturi vacuum. The velocity of the air moving through the venturi. Back to the perfume spritzer that is used as the basis of how a carburetor works. Squeeze the bulb gently, light spray of perfume. Squeeze the bulb really hard and you get a big shot of perfume. In that case it is the exact same volume of air passing over the venturi. The difference in the amount of delivery is based on the velocity of the air passing the venturi, not the volume of air. Now take the same carburetor and put it on a bigger engine. Volume increased, same size carburetor, so the air has to flow through faster. The faster air pulls more fuel per volume of air. You are now pulling more fuel in 2 ways. One is the more air that needs fuel, second is that faster moving air pulls through the jets stronger."

I'm certainly no expert.  I probably never would have thought to jet down in size without reading similar posts...and my bike is definitely running better as a result.
 

This is really interesting and certainly goes against conventional thinking but you know how your bike runs   interestingly if you look at a stock KZ1000 (J motor) as far as I am aware the only difference is the "J" has more lift on the cams than the "K" or "M" however the manual lists "smaller" pilot air jets but "bigger Mains" for the higher performance model (bigger cams = more flow) go figure !! 
Would be interesting to see what the stock jets are in a 1100 (bigger capacity and hotter cams than a "K" ??