Hi everyone,
I am about to order and install Bill Blue's 351 kit on my 2012 model and I am considering disabling or removing the ACR. Bill isn't sure it is a good idea since the compression ratio with his kit is 12.5:1 but I wanted to reach out here to ask if any 351 owners have either removed or disabled their ACR and if so, if there were any issues related to that.

Any help with that question will be appreciated. Mike

 

Why would you want to remove or disable the ACR?

Ride on
Brewster

 

To eliminate it from coming apart, from slinging its spring, to eliminate some weight from the cam. Many have removed it or disabled it from the 250's according to what I have read on this forum.

 

You will be the first - the pioneer - regarding this experiment..

Just know that there is no historically supported reason to disable the KACR without cause - cause being the MCM. And, luckily, we have found that, on a stockbore, the starter does not falter with the KACR disabled.
Your mileage may vary (on a 351)..

 

Well, seems in the MCM thread Marcelino pointed out that even stock, the specific engagement/disengagement wasn't exactly primo. In other words it bled off a bit much compression. So I figured disable it. Now I can't prove it works better, since I had done jetting, valve adjustment, and MCM around the same time, but what I can tell you is it isn't necessary on a 250 and probably not on a 351 either. I cranked my bike over in single digit temperatures here in Ohio and it fired up quickly. Even with cold oil it wasn't a big deal starting. So one less moving part in the engine. Owning a KLX650 with the same kind of compression release mechanism that has been known for dropping springs and grenading the mechanism, a number of riders in the old Yahoo KLX650 group took it off the bike and said it wasn't too bad. The 650 definitely works a bit against compression so we reset the rivets which were a bit loose. It still dropped a spring on me a second time. First one was in the crank case the second was still laying in the head. I changed the direction of the hook of the spring and it seems to have stayed on well now.

The CRF250L and the WR250R does not have a compression release and they run up to 300cc big bore or stroker. That and with the performance of my bike I'd have to say it's a left over appendage from the kick start 250/300, and really is unnecessary. But that is simply my opinion, I didn't bother with any special verification other than starting the bike in temperatures near 20° below freezing... good enough for me.

 

The WR250R does have a decompression feature on one of its cams. # 5 in the parts photo: https://www.bikebandit.com/oem-parts...769#sch1086550

I haven't seen one and don't know how it operates so it may not equate to the KLX ACR.

Ride on
Brewster

 

I'm wrong, you're right, I looked at one time and missed it. Not the first time, won't be the last. I don't know how it works either, just know my KLX does fine without any help and that some of the KLX650 guys actually have done away with them on their bikes. I just thought that the 650 fought a bit too hard for me to be confident it would go without. No problem with the 250 though.

 

While the KACR probably does diminish starting efficiency somewhat in drawing cold start fuel mixture into the cylinder, it seems a bit of overkill to remove it. As long as the carb is set up properly or in the case of fuel injection, I think the KACR has more benefit than detriment.

I've noticed on some of my trips to the hinterlands on cold mornings in camp, even with a fairly new battery, you can tell the engine cranks slower even with the KACR. Why challenge the starter with even more resistance? Also, since we only have e-start in OEM condition, when I'm way, way off from camp on a trail in the middle of nowhere, I want life for the starter and battery to be as easy as possible.

Think about how long the KACR has been around in how many bikes. It has proven to be reliable and durable. However, that doesn't prohibit people from setting up their bikes any way they see fit if they want to remove it.

 

Since it doesn't seem that it has been done on a 351 and Bill didn't support it, I will probably just remove the spring at first and see how that goes. That way, if it seems detrimental without it, I can easily just re-install the spring.

Thanks all, Mike

 

If you ever have to push or bump start the bike, you'll want the ACR to be functional.
If it ain't broke, don't fix it!

Ride on
Brewster