PREFACE:
I have an 09 KLX250SF which has been ridden for 1 year, 8,000km, & it has had the typical cold starting issues since new. As remedies I have tried shaking, laying down, new plug(s), new battery, drilled starter (.018 & .019), slowly pulling choke while cranking, & checking valve adjustment, none of which have provided THE cure. I currently have a primer bulb mounted in the fuel line which helps immensely but it’s simply a band-aid & I’d like to investigate the next likely culprit: the KACR. The shop manual is silent on the KACR other than to assure the reader that there is no user-servicing required. I have also found little conclusive discussion on the effects of working on the KACR by searching KLX forums.

QUESTION:
Is there any testimony from anybody who has performed any work on the KACR in relation to cold starting? Specifically:
• Did you adjust, replace, disable or remove it?
• How?
• Did the work correct the cold starting problems?
• Did the work have side negative effects such as difficulty cranking, warm starting problems, or valve mis-timing?

I’ll be digging into the KACR in the near future but I’d like to first hear from anybody who may have already done this. Thanks in advance for any substantive feedback…

Typographical errors by iPhone

 

I think Brewster who posts here occasionally has a mod for the KACR, but I can't remember if it was for starting issues or other reasons. For your starting issue, you're trying to prevent the KACR from releasing too much compression which could make for harder starting. Have you done a compression test with the KACR as it is? If you have over 120psi with the KACR in place, I doubt it's your problem, but I won't swear to that. Refresh my memory from your earlier post and the similar posts already on the forum...did you check your valve adjustment?

 

@TNC: yes, valves checked & in spec.*

I can confirm that the compression 'feels' good by hand cranking. I have a compression gauge somewhere in a box and if/when I find it, I'll obtain a reading and report back.

I can find reference on this forum to Brewster discussing 'grinding the pin' on the KACR, but no confirmation on the specific procedure or results...

Typographical errors by*iPhone

 

The "grinding the pin" is not something I have done or advocated. I believe that what I posted was a question like "what the heck are they talking about?" There is no pin to grind on the ACR. What I've done to about 130 cam/acr units is remove the acr, retard it about 10 degrees (cam timing) and press it back onto the exhaust cam. This retiming was done to cams from the mid 2002 model year KLX250s and KLX300s. Some where in the 2002 model year, Kawi changed the acr timing to close to where I reposition it.

If valve clearances are good and proper kicking technique is employed and there is still problems getting the engine to fire, the carb is the first place I would investigate. I've had a 36mm Mikuni pumper carb on my bike for many years with no starting problems. The stock carb did have its moments.

Ride on
Brewster

 

@Brewster: Thanks. The Carb adjustment checks out fine with the proper float level, main jet/needle to match my TBR slip-on & Uni filter, and as mentioned the starter jet has been over-drilled. Except for cold starting it runs flawlessly, hence my focus on the KACR.

@TNC: Regarding performing a compression test with a KACR, how is this accomplished? The two seem mutually-exclusive.

Being a single cylinder engine, it will not be possible to perform the test with the engine running because, by definition, it will not run with the plug removed to install the compression gauge. By extension, if one is relying on the starter to perform the compression test, the KACR will be in effect, and provide a false (low) reading because compression is being released during the compression stroke.

The only workaround I can think of is to remove the valve cover, fool the KACR into thinking it’s spinning at idle speed by jamming it, and then perform the compression test. Is this what you did when you tested your compression?

Typographical errors by*iPhone

 

If Brewster's mods are not applicable for most of our bikes (2003+ if I understand him correctly), then what are the Kaw dealers doing to the KACR to fix starting problems? Are they "grinding the pin" /lever/bar that presses on the exhaust valve?

Looking forward to hearing back on compression test.

 

No, the manual shows that you can do a compression test with the KACR...at least I'm fairly sure that's with the KACR still operational. It says it will yield between 64psi to 127psi designated as useable compression. Without the KACR, I'd think our 12:1 setup would produce somewhere around 175-200+ psi...some speculation on my part...but I think it would be well beyond 127psi. I tested mine with KACR attached, and it produced 125psi when it was a 250. I did this, as I was always curious what kind of reading you'd get, and I had owned several KLR600/650's with KACR. What I'm suggesting for you is to see if yours has a compression reading close to 120psi. If it is then I think you can assume the KACR is doing its job without bleeding off too much compression. If it's noticeably lower, then maybe you do have an "overactive" KACR or some other issue affecting compression...and perhaps then the solution to your problem. Do you see what I'm trying to describe here?...or maybe I'm missing something...wouldn't be the first time.

 

So you didn't try the "run the gas out before parking" Hmmmmmm

 

@TNC: I see exactly what you are trying to describe, and thanks for providing the manufacturers’ compression range. It wasn’t my intention to have you doing my research for me but I appreciate it! Kawasaki has obviously built a ‘leakage-factor’ into their numbers to account for the KACR. For the sake of argument, I suppose another method for obtaining a truer compression reading would be to remove the header pipe and plug the exhaust port with some kind of an expanding rubber plug, or shove a squash ball in there or something…

@deej: I did also try running the carb dry and it does in fact work! Likewise I have also found that any time I have replaced the carb after removal for service, it’ll fire right up no problem that first time. I just don’t it an acceptable solution to the problem…

Typographical errors by*iPhone

 

Do you know what your "true" fuel level is with the clear tube method outside the carb?