True. I had forgotten about bump starting. Though it's a rare need to bump start, when/if it happens it could be kind of critical that the bike can be bumped started...out in the boondocks, not in your garage. Even with KACR it's a bit of a bear to bump start a KLX.

 

I just left the KACR in place when I installed my 351. The bike starts so easily either before the 351 and after that I can't see why I'd want to remove it.

 

You guys are right, it is totally up to the rider. My comment included why I did it . Seems several of the riders at the Yahoo KLX650 Group had the rivets break and the engine ingest the shoe with rather disastrous results. I had two springs come off, one was in the crank case when we redid the top end, the other was in the head when I took the cam cover off to find "the noise". So I disabled the one on the 250 and found it had no effect for my use. Then I did test it starting in some serious cold - near 0° just to see how it would turn over. No problem. Not saying everyone should do it.

As far as bump start, I've done my 500 single quite a few times goofing around no compression release, no problem. Before all the remote starts it was the way flat trackers did it. Clutch engaged, rock the bike back against compression and in second gear, roll and bump As small as the 250 is, rocking back against compression will give plenty of momentum to overcome the compression of the 250. It did on the SR500. And you are assuming the compression release will function adequately when trying to bump start. I don't know if it does. If the spin when you engage the clutch gets the cam rpm too high it won't work. I know the 650 wasn't the easiest to bump off, locking the wheel unless I dropped my butt hard on the seat when releasing the clutch.

So that's my story and I'm sticking to it...

 

I removed my KACR spring when I did the MCM on the stock bore, and left it out when I went BB351. In under 10K miles with the 351 the starter needed to be gone through by a local motor/alternator shop. Wouldn't start with a new battery and all connections were good. Cranked right up after the shop worked their magic. I bought another spring and plan to install it soon. Guess I will see how she starts then.

 

There we have it. Thanks Snappster.. That's one failure VS decades of NO reported failures/issues with KLX starters.

For those that can learn from one "data point", disabling the KACR on a 351 will lead to starter failure.
For the others, go for it ! Yank off that KACR spring on your 351, I dare ya..

 

Do not take this as meaning don't to the compression release, I am saying the failure may have had nothing to do with the big bore or it may have everything to do with the big bore. From what I gather you did not find out why? No research no knowledge, just a guess based on one instance. I would definitely want to know what happened and what could have caused the problem.

What you are saying is that the starter spins the engine effortlessly. Fires right up. Is there no real difficulty spinning the engine and starting? Seems to me if not having the compression release was an issue the starter would be laboring when turning the engine over. My 650 labors in spite of having the ACR, where my 250 spins like there's nothing there without the ACR. Did you ask the starter repair company what was wrong with the starter causing the need for the repair, what they did, and why they think it may have happened? Riders have starters fail on unmodified bikes. It's electric, one small flaw, one nick in a wire or flaw in a starter brush can fail at any point in time. I'd want to know what and why.

I had a starter go bad on my Nighthawk S with around 10,000 miles. No modifications, starter just failed. A brush failed, cracked and broke. I had the armature turned where the brushes had contact to smooth the surface and did another 10,000 trouble free miles before I had to sell the bike. Starter issues were not a common issue, but it happened on my bike after 10,000 miles. That Nighthawk starter should have worked for tens of thousands of miles, but it didn't. Electrical component failure isn't absolutely predictable by any stretch. Thing is I know what happened. It had a faulty brush that failed.

If one data point, without knowledge, as a reliable predictor I should have been on the PBA bowlnig tour, I had a strike with the first ball I rolled down the lane. Unfortunately one data point wasn't a good predictor there and isn't very sound in this case without some additional information on what happened. Maybe you know, but didn't say why in your post. I don't know.

If we used one failure data point for the MCM no one would be doing it. There were riders who claim negative effects. Fortunately there are dozens who contradict the one or two negative data points.

 

I'll edit my post above to provide the information you haven't thought of / didn't consider.

Thank goodness we no longer have to rely on DynoButts to know what the MCM offers in performance benefit...

 

Were you the one with the 351 that had a bad starter? I thought it was someone else.

 

I looked at my vehicle maintenance record and discovered that my starter only lasted around 5000 miles with the BB351 with ACR disabled, not 10K as I posted earlier. Plus or minus 1K because I did not record the mileage properly when I did the BB351 but deduced it from prior posts. I recently created the spreadsheet because I was tired of guessing how long or how many miles had been driven between air filters, oil, batteries, tires, etc. The miles on the bike when I installed the refreshed starter is correct at 22460. I guess I disabled the ACR around 10K and the BB351 done around 17K.

 

Hi just wondering i have the MCM mod on my BB351 Question is will the KACR work with the MCM mod i find it starting hard with no KACR i took the spring off the stock 250 n was good but kept hearing a slight ticking noise it seemed to be comming from the unsprung KACR do cut it off the cam but now with bb351 i think i probly should have left it they but iam not sure if i get another KACR if it works with MCM ?
Any thoughts and i have no idea how to work this forum iam like 10mm socket in da bottom of a sump