Hey thanks for all the repsonses - it seems safest to leave the KACR alone when I big bore, keeping in mind I can always disable it again if needed with little more effort than removing the valve cover.

As far as the MCM with the big bore, I had thought there were concerns voiced, whether substaniated or not... again, probably safest to start with the timing straight up with the big bore.

Klxster - VERY thought provoking when you point out that the big bore and MCM produce low rpm torque and what the combination of the two might be versus what breathing limitations might exist with the 351 breathing through stock ports!!! I have also noted your tuning recommendation and will keep it handy when I do the BB.

IDRDR - Tks for the specific answer to my big bore/KACR question. Does your bike start well? It seems the "classic" KLX starting behavior is probably tied more to the CVK than the KACR, so I'm gonna go out on a limb and guess that your bike starts fine with the MIkuni! (As Dash8's does with a MIkuni)

LemonRX - I know white powdery color on the spark plug indicates lean, but that doesn't seem consistent with a lot of carbon on the top of your piston. I do try to make mental notes of the tuning specs I see in signatures and had noted that your 132 MJ with the stock bore seemed rich from my experience near Sea level. But with so many other variables like air density and fuel grade, quality, and ethanol content, I figured you were get away with it where you are. Similarly Klxster's 140 MJ combo seems kind of rich from my experience here in NW WA State but works real fine where he is.

Doc46 - Good reminder that as good as Bill can get on paper, real world is what works where you are! Solely for monetary reasons, I am planning to do the BB this winter and see how much satisfaction I can get out of the CVK, knowing that the Mikunis are proven options as future upgrades.

Alas, the conservative side of me still sorta leans towards the 331 kit but there is clearly far more shared tuning experience and "baseline setups" for the 351...

Tim, I agree with your choice of leaving the stock cam timings and keeping the KACR functional. There should be more than enough TRQ below 6.5K with stock phasing - and no doubt, stock phasing could only help the ports and valves and cam lobes feed the 351 better above 6.5k..

I have no idea how to properly fuel a 351. You'll certainly want to run lidless for max power but no one knows how the CVK responds to the increased "signaling" a 351 would offer - though there has been a lot of armchair opinions - there is no AFR charting/measuring to give us any real idea/proof.. All I could offer is a "best guess" after research and running thought experiments..

Doc46 I had thought about drilling it, but definitely not while it was sitting upright in the bike. Eventually I decided to just leave it, and this just further supports my decision. I won't be drilling anything. I'll run a separate line from the crankcase to a smaller air filter and leave it breathing somewhere else. I don't ride in the rain or through any wet/muddy areas (yet) so it shouldn't be a problem. However I do keep all my stock parts should I need to revert. I bought a torque wrench several months ago preparing for all of this. Got it covered. I'm also doing the pumper carb at the same time, but since I moved from Wichita to Stillwater, elevation has changed. I'll do the heat cycle, run the break-in, then I'll be taking it to a shop to get it dyno-tuned and rejetted as necessary.

timc63 I spoke with Bill today about exhaust and he recommends using the Barker system he sells, or running the stock header with the Q4 muffler. He said the stock header provides more low-end torque, while the Q4 allows more power midrange and up high. Personally I have the PowerBomb and the Powercore 4, and I love the sound it provides. Loud by itself, but quiet around some other bikes. As far as the lean/rich goes, it might have been a little rich back in Wichita, and I've only had it with me in Stillwater for a couple months, but in that time there has been lots of popping on deceleration, and there are times when I don't let it warm up properly before riding to work. The elevation between Wichita and Stillwater is only 500 ft difference, so I didn't think I would need a rejet. Mistake on my part, but it'll be fixed when I get her back together. When I move back to Wichita, I'll have Bill himself run it on his dyno to get the maximum power.

He's also been working on a big bore kit and carb setup for the CSC adventure bike.