Bill Blue 331 cylinder compression?
 

Can someone tell me what compression reading should be on a Bill Blue KLX 331? I'm getting about 125 PSI. The service manual specifies 96 to 149 PSI for the stock engine...

Correct me if I've forgotten, but because of the KACR doesn't Kaw provide a range of something like 64-127 psi? I don't think you get a true, absolute compression reading unless you disable the KACR. Isn't that the case? When I checked mine, it was about 125 psi.

Another variable in the compression reading is the stock CVC carb. With the slide down, there is a restriction on air getting into the cylinder.

Ride on
Brewster

My Kawasaki service manual for the 250S says 96 - 149 PSI (for stock engine). Glad to hear that you also got 125 on your 331! I guess my compression must be good then lol... thanks! I was checking because I've been trying to diagnose a problem with the header pipe glowing bright orange during extended idling with choke on and on main jet operation (higher throttle openings/higher RPM). It only started doing that recently (2,500 miles on 331 now).

I've checked the oil and coolant, air filter, air intake track (both sides of carb), cleaned carb, tried different jets, messed with a/f screw, checked exhaust pipe and muffler for restrictions, tried different pipe and muffler, replaced spark plug and ignition coil (it appeared physically damaged which made me think that was the problem...it wasn't...), you name it. I spoke with Bill about it today, and he suggested it's got to be something in the carb causing a lean condition. Even though I've had that god damn carb in and out 4 or 5 times, I think he might be right. I may have missed something when I went through the carb; Bill gave me some great tips on how to THOROUGHLY clean out a carb. So that's what I'll try next.

Strangely, I haven't noticed any performance issues - no stumbling, hesitation, rough idle, hanging idle, poor throttle response, power loss - none of that, bike performs flawlessly other than being a bit of a bear to start (although I finally came up with a system for that which works every single time without fail...). But the starting problems I always just chalked up to the combination of crappy stock carb and KACR. The bike will pull the front wheel up sitting down in second gear, without clutch slippage, so I'm pretty sure there hasn't really been any bottom end or lower mid range power loss. But I suppose it's possible the top end and full throttle stuff could be down a couple horsepower from being lean up top... It does feel relatively weak above 7k RPM, not much stronger up there than the stock motor.

If you back off from WOT to 7/8 throttle or so and it speeds up a little-it's lean. If it stumbles it's rich.

I remember some bike I had decades ago would speed up when I backed off WOT and I always wondered why a bike would go faster at less than WOT

kj, is your exhaust air injection system still connected?

Do tell, please.

Not totally familiar with that terminology, but from what you're saying I think you must be talking about the charcoal canister and all that "smog crap". IIRC (and understood), part of that system re-routed some of the exhaust gas back into the airbox? I removed it all and plugged the two lines coming off the carburetor, installed Bill Blue's "fresh air block off plate" with the gasket and some RTV, and connected the two tubes coming out of the air box with a piece of rubber hose, so as to block them off. I have an aftermarket fuel tank with only the "main" and "reserve" lines, and the one vent hose on the cap.

Carb Cleaning 101
 

<<<@!1!@>>>


1.) Soak in a vat of carb cleaner (he didn't specify time but I'll probably do at least 12 hours, maybe even 24 just to be sure (EDIT: The Yamalube carburetor cleaner dip says 8 hours max)...). Before this step of course I will have completely disassembled the entire carb - all the parts will go into the vat.

2.) Pull everything out of carb cleaner solution and straight into a bucket of warm water (I may use boiling water - need to read up on that possibility a bit more)

3.) Spray out all jets, passages, openings, and accessible surfaces with spray-type carb cleaner

4.) Repeat step 3 using compressed (high pressure) air

5.) Be sure the carb is fully dry before reassembly (Bill didn't tell me this...but I will do it; Also, I did add some details here to the basic steps Bill suggested - above - as to how exactly I will go about it)

He also suggested taking the rubber diaphragm thing on the top of the carb (whatever it's called) and holding it up to a light so the light is blocked, then GENTLY stretching the material to see if any tears or pin holes appear and let some light through. He said that would cause a lean condition. That would of course mean replacement of that part.


He recommended this for a carb cleaner: http://www.walmart.com/ip/Super-Tech...tlyViewedItems

Unfortunately for me, I live in good old California...and they won't let us buy that stuff here :(

Since I can't use that, I'm in the process of searching for both a good spray-type carb cleaner and a soak-type carb cleaner solution. Being very careful here because I understand that some "cleaners" can do more harm than good in the long run, and some just plain don't do anything. In search of the best product available...

***EDIT: After a bit of quality research, I'm going with the products below.

For the carburetor cleaner dip (in which I'll dip the disassembled carburetor): Yamalube Carburetor Cleaner Dip -

For the spray-can of carburetor cleaner: PJ1 Professional Carburetor and Choke Cleaner -

If your rubber diaphragm expands and won't fit easily into the groove, soak it in HOT water for 5 minutes or so. It will shrink and stiffen, making install easier.