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I have been working all winter on my KZ440 LTD café racer. I pulled this bike out of extreme neglect conditions from the original owner. As far as carbs go I had to purchase all new diaphragms, needles, jets etc.. Had to purchase a new tank as the previous one held almost a pound of bondo. It has new MAC 2-2 exhausts, and I recently just adjusted the valve clearances.
My problem with the bike is it is running extremely lean since I put on the new MAC exhausts. These are NOS pipes, and MAC informed me these might have to be rejetted. Currently the bike has the stock size 88's on the mains. Should I go up to 90 or 92's ?
I put new plugs, and let it idle for 5 minutes and they are a little white. I put a second set of plugs kept the engine at half throttle and are also white. When you let off the throttle the exhausts pop as the bike slows down.
I feel the stock air box is restricting the air, while the MAC pipes are allowing more air to escape. Should I shim up the needle, or raise the main jet ?
Keep the stock air box for now. It will run worse with the current jetting.
Aftermarket exhaust are single wall tubes. The stock factory tubes have
2 tubes to help protect the chrome. Hence the the aftermarket exhaust
is less restrictive and requiring rejetting. I recommend seeking out a
Sigma jet kit for a 440 with a stock air box and free flowing exhaust.
They are not a 'complete kit' but a viable alternative that comes with some
good instructions for a novice in carb rebuilding. They are the only
option for a lot of the 'less popular' bikes when it comes to a kit that the
other companies do not cover. The exhaust popping indicates a lean condition.
I purchased a sigma jet kit when I first dug into the carbs. In the kit was 97.5 jet a 102.5 jet, needle shims, drill bit, and instructions. Since I am only going for new exhaust and no pods I installed 97.5 and the bike went rich.
I purchased a sigma jet kit when I first dug into the carbs. In the kit was 97.5 jet a 102.5 jet, needle shims, drill bit, and instructions. Since I am only going for new exhaust and no pods I installed 97.5 and the bike went rich.
Some more basics, did you install new carb boots? Float level? Fuel filter?
If those issues have been addressed I would try a happy medium between
the factory and the jet kit sizes. The Sigma6 kit I installed was a little lean
for my application. When I rejet I start with getting the idle set. Then move
top end with the main. Last with mid range and the jet needle and needle jet.
+1 on basics first. Check for rubber manifold leaks (very common) which will cause a lean running condition; spray some WD40 on them to see if the rpms change. Spark plugs standard NGK units or hotter range? Running an OEM filter in the OEM box? No sense changing jets/carb circuits until everything else is sorted out. Just adding a MAC exhaust (and still using the stock air box) should not cause a lean running condition. If you do go to pods, use good quality units not the cheap EMGOs (BTW - going to pods will not improve engine performance, but will cause all sorts of time/expense re-tuning the carbs, avoiding wet roads, etc.; lots of experience on the KZ Twin Owners Forum say so).
Yea, the "H" provides some additional scavenging but not that big a deal. Some of the old KZ400s also had a 2-2 exhaust from the factory w/o the "H".
When you say that the carbs are completely clean, I'm assuming that you are also talking about the idle jet circuits under the removable plugs (with "O" rings) and the idle mix needle assemblies under the pressed-in plugs. What are the idle mix needles set to? Should be about 2 1/4 turns CCW out from fully (lightly) seated - as a start. Tune for max RPMs. Fuel level is best measured with a length of clear tube connected to the drain and held to the float bowl. Fuel level should be about 1mm below carb body/bowl joint. Each carb circuit works with the other circuits so if the idle is a little lean, it will affect the rest of the range too; if the float bowl level is too low it will get leaner much faster (probably cut out at higher RPMs too).
How is your advancer unit (under the old points cover)? If it is rusted/frozen at full advance this might help cause the hot plug condition too (most times it is rusted/frozen at no advance). Make sure it is clean, lubed and moves freely.
I replaced the gaskets on both engine covers, and the advancer was free not rusted. I replaced the idle screws with o-rings on the carbs, with the ones provided in the rebuild kit and backed them out 2 1/4 turns. The guy at the kawasaki dealership had the old school kawasaki float gauge tool that looked like a syrenge hooked it up to the bowls, and determined they were correct level.
Thanks for everyones help I want to get this mother ready for Mods and Rockers Cincy in June.
Given your previous post's results with the replacement main jet, I'd validate the float level in each bowl, tune the idle mix for max RPMs (probably closer to 2 3/4 turns CCW) and then sync the carbs. FWIW the stock jets should have been 62 for the main, 88 for mid-range (with a NO2A needle) and 35 idle (USA specs). Other markets had different jets (with West German market also having different air correction jets and 32mm venturi versus 36mm for everyone else).
OK I corrected the float levels, and the bike is still running lean with these MAC exhausts. I received a pack of 90, and 92 jets. Currently the bike has the stock 88's.
Did you adjust the idle mix screws for max RPMS (should be closer to 2 3/4 turns out or so)? When the carbs were apart, did you closely check the carb diaphragms for any pin holes?
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