Installed pod filters & open exhaust & now I get HORRIBLE mpg

what is stock mpg?

With pod filters and open exhaust the mpg goes down?

Is the only way to get the stock mpg is to go back to stock air box & baffled exhaust?

I am confused - do I need a jet kit (which stage) or carb rebuild kit?

Post edited by: elcid, at: 2008/03/02 16:56

Post edited by: elcid, at: 2008/03/02 16:56

I like my machines to be stock. It is the way the engineers designed them. You should be able to run pods and an open exhaust without much of a mileage change, maybe 3 or 4 mpg reduction (also depends on how you drive, and other factors). Once you get the carbs dialed in, it should run and sound great. The posative thing about having pods while you are messing around with the carbs is that it is a heck of a lot easier to yank the carbs off. You will be doing this, on and off, if you plan to do it yourself-Which you CAN and should with all these open ears and eyes on this site, you can do it. And it will end up being more fun and cheaper. But when you give up, there is always Wiredgeorge!!

what should a stock kz650 mpg be?

do I need a jet kit or rebuild kit??

Mine is as stock as they get:
i157.photobucket.com/albums/t43/benfs/IMG_0031.jpg
Exact same as the bike pictured on the stock shop manual. Get one if you don't have one, a clymers will work.
I hope to get around 38mpg, but I tend to rip it up alot, this affects mileage in any vehicle as you know.

You need the correct main jets, not kits. Four of them being the same jet # Stock sea level is 102.5's, I think. Take off your carbs and open one of the bowls and see what you got in there. It sounds like something else is set wrong and you are pouring way to much fuel into the cylinders, some of it not even burning. Are all the headers getting hot? If all four cylinders are not firing, this could really reduce efficiency and mileage and you would smell unburned fuel coming from the exhaust, perhaps like you said . . . Also ask the mechanic if he adjusted the main jet needles, which could also be part of what is going on. I think stock is second notch from bottom on the main needles. It's in the Kawasaki Shop Manual.

elcid wrote:

what should a stock kz650 mpg be?

At least twice what you're getting now. My bike gets about 35mpg with K&N pods and a Kerker 4 into 1 (with baffle, without end cap). Your fuel economy will potentially decrease because you're processing more air and fuel in order to get more power, which is why you change the intake and exhaust to be more free flowing. When you go to a free flowing intake and exhaust, you have to increase the amount of fuel in order to maintain proper air/fuel mixture. If you don't rejet, your mixture gets too lean (too much air and not enough fuel), which can lead to burned valves. Learn how to do a plug chop and how to read your plugs.

do I need a jet kit or rebuild kit??

Probably both. You don't always buy jets in "kit" form: you just buy the jets you need and put them in.



If you haven't rebuilt your carbs yet, you should get four rebuild kits and go through them. A Clymer manual will get you through the operation, but I much prefer the factory service manual. Search eBay, I think I gave $20 for mine.

Learn how to set your float height, as it sounds like yours is off.

Stage I, II, III, etc. This refers to the level of performance you're going for, and the changes you make to achieve this.

To the best of my understanding, it goes something like this:

Stage I would be something like a drop in K&N filter in your stock air box. This will flow more air, so you'd probably need to go up a size on your main jets.

Stage II would involve switching to pods. They'll flow even more air, so you'd need to go up on the main jets again.

Stage III would be switching to a Kerker or other free-flowing exhaust. Again, more air flow means you need to flow more fuel, which means larger jets.

Stage IV would involve porting & polishing the intake and exhaust ports in the head.

Stage V might be something like larger valves made of stainless or titanium or something like that.

And so on...

None of this is cut & dried. Somebody probably makes a Stage Whatever kit, in which they've assembled the parts they think you're going to need, but it's never going to be that cut & dried. You'll always need to make adjustments based on what you find after you make the changes. That's why they call it "tuning": you're always trying to zero in on that magical balance to get the most out of your equipment. It's like the scientific method: you make X change expecting Y result. You make the change, examine the outcome, try different things and see what results you get, then repeat the process. (It's a journey, not a destination.)

Rather than paying a mechanic to do this stuff, you need to learn as much about your bike as you can and figure out how to do it yourself. Luckily, there's this forum with a bunch of other people who've done this stuff before who're willing to share their knowledge.

You really need to spend some time searching the forum for previous discussions, too. Most of this stuff has been covered before...

Post edited by: guitargeek, at: 2008/03/02 18:20

If you are working with a mechanic, I would rely on him to find the necessary parts and jets, to rebuild and properly tune the carburetors. Good luck with your mechanic.