You are definitely a perfectionist, few people would go the trouble to measure again valve clearance.

I think your results prove that what Kawasaki publishes in their service manual is somewhat arbitrary. It might be referenced to 10mil lift or so, and would vary greatly with clearance variations. Plus, air flow is probably very near to stopped at 50mil lift anyway, for a valve that lifts 350mil or so.

 

No, not a perfectionist, I had the shims out earlier and just wanted to make sure I put them back in correct bucket....

I'm still trying to figure out why it won't run at full throttle under 5000-5500 rpm. It acts more like it's mis-firing than lean or rich. I've checked the coil, spark plug, cdi, valves, valve timiing (that's why I originally put the degree wheel on it.

This motor has always run perfectly, except a little lean at full throttle (with a 128 main jet), and most comments I've read, said that they had to go richer on main jet after the cam mod, so I went up to a 135,(wouldn't run at full throttle) so I went back to 132,,,, saw no change.

I'm an old 2 stroke man, (CZ, Husky, Montesa and a few Yamaha's), so I'm fairly new to 4 stroke motorcycle tuning, but I built automobile drag race engines back in the 1960's and basics are still the same for bikes except for cdi and fuel injection, but mine is a carbureted version, so........

I thought it might be a weak spark, because of the higher compression pressures at lower rpm's, but my ignition will jump a gap of 6 mm (through a resistor plug), and that is more than factory requirements and should be plenty to handle these pressures.....

If I wasn't so dammed hard headed, I'd give up and put it back to stock cam timing...

 

I have no idea why you can't jet your engine properly with your configuration, it might be a bit tricky (assuming it is really jetting that is your problem). I find that using a lambda meter for that is not luxury, it helps eliminate that guessing work (more so because I am not good enough to distinguish between a lean or rich running engine).

That's why I installed a KLX300 exhaust, with a bung plug welded to the mid pipe, to which I screw a Bosch wide band lambda sensor, connected to a Motec unit. I also use a data recorder and perform 3rd gear runs at quarter throttle, mid throttle, three quarter and full open. It requires only a few runs to adjust my air/fuel ratio like I want. If you were close to me, I would let you use that equipment...

 

Yea, the lambda is the best way to tune, but I don't have one,,,,,,
I am getting closer though,, after eliminating all ignition components, I went back to the carb.
I first put some tape over 1/3 of the air inlet to filter and it got MUCH worse, so I then removed the lid and it was much better, so I went back to the 128 main (which was lean on the stock cam timing), and the bike runs good.....

My confusion now is why everyone else had to richen the carb and I'm 1 step leaner

 

Congrats.

I think single cylinder engines are more sensitive to exhaust and intake resonances than multi cylinders. Even those small resonances that do not influence greatly the total air flow may change the amount of fuel pulled from the jets. Thus everyone's configuration might play a role...

But my favorite explanation for those strange things is that you are probably close to a recent meteorite fall

 

I'm glad to hear that,,,,, I thought it was my old-timers-disease......

 

Your post is too long for me to read. But it looks interesting.I may learn a lot from your post.Thank you anyway.

 

i have a klx 250 1997 with cvk34 carb and i did the cams mod resently. Now i have the same problem with john65. and i was wondering if john found a solution or changed the cams back to their original position. and also if i can convert it to fuel injection to eliminate the carb jetting problem. any help will be appreciated

 

You guys are talking jetting, but not listing the type of jets yoiu are using... keihn/dyno/mikuni/kawa jets are so different you need to indicate what type you are using if your trying to share info.

 

Yes, I did solve my problem, and I still have the cam mods, (except for the acr change). I just removed the spring from the acr, which disables it. By doing this, if I later decide to go back to original cam timing, it will only take about an hour to do it.

The solution to my jetting problem was to go back to my previous jetting.
I am using a 38 keihn pilot jet with the adjustment screw at 1 turn
( a 35 pilot with adjustment at 2 1/2 would probably be as good or better)
I'm using the stock jet needle with a .020 shim under the head.
using a 128 keihn main jet, with snorkel removed and lid on, but air inlet is opened up to approx 1 1/2 times original size.
The spark plug still indicates rich mixture, but the bike runs good and I'm tired of removing the carb, so I'm leaving it where it is.

The low and midrange torque is so much better that I have no intention of going back to stock timing.

BTW; I'm only 200 ft above sea level.
and I also have stock exhaust, but modded last baffle in muffler and install a 1 1/4" stinger (tail pipe)