Cam Advance MC Mod. - Page 10 - Kawasaki KLR 650 Forum
2008+ KLR650 Wrenching & Mod Questions For repair, maintaining or modifying discussions related to the newly updated 2008 and beyond, Generation 2 KLR650 Motorcycle.

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post #91 of 95 Old 04-26-2017, 11:49 PM
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Join Date: Aug 2016
Posts: 527
That makes sense. Yer a smart cookie. :thumb
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post #92 of 95 Old 04-26-2017, 11:59 PM
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Originally Posted by shinyribs View Post
That makes sense. Yer a smart cookie. :thumb
Thanks, but . . . my postulations play to DECIDEDLY MIXED REVIEWS!

I thought piston displacement vs. crankshaft rotation varied; minimum at BDC and at TDC; maximum halfway between the two. If that premise is correct, then the crank angle where the KACR cracks the valve would affect the magnitude of the compression released, or so it seemed.

The MC Mod moves the angular point of operation of the KACR by 15 crankshaft degrees; I'd expect some consequence from the change, but . . . maybe not!

Last edited by Damocles; 04-27-2017 at 12:07 AM.
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post #93 of 95 Old 09-24-2019, 09:59 AM
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Join Date: Sep 2019
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Shinyribs, have you done the advance mod...yet? Your point about doing valves while in there is a valid point if they were to tight to begin with this could cause a loss of compression and power. If they were a couple thousands looser than factory specs i cant see how that could make much of a difference in the 7-10% change in power? I noticed the low end torque change the most, dont venture into the KLR zone much on my 09...

Full choke on cold starts with no throttle cured the hard starts usually fires right off, no choke and a slight twist on hot starts usually works to avoid the clack clack depending on where that piston is..... The slight twist is a like starting an Old Norton after you bring it to top dead center and a long serious kick on the lever if the twist is a little off....its kicking time! Having that kick start option on a second gen would be nice.

You guys who have given theory and factual ideas of ICE engines and cam functions is quite interesting! I guess this is one reason why this forum is so good, adults having conversations!

Last edited by Retfird; 09-24-2019 at 05:08 PM.
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post #94 of 95 Old 09-24-2019, 12:11 PM
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Join Date: Jul 2016
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Here is my take on why I feel more "power" after the MC mod. I ride at relatively low RPMs. It is rare if I rev past 4500. I found that between idle and my normal 4000~~ ish shifts the engine seems to pull harder and faster to those levels. From what I have read in earlier posts this makes sense. Long duration/long overlap is great for high RPM, an area I very rarely use. When I stated I feel more power throughout the rev range, it was my rev range. (see above.) It makes sense that closing the exhaust valve a little early would boost the torque, and that is the difference I am feeling. I don't think this would work to well on a Ninja 250, unless you never spin the engine up to its crazy redline. I can count on 1 hand the number of times I have revved over 5500 RPM in my 73000+ miles with my KLR. Power fell off fast above those RPMs so I never go there. I the question that was posed that led to ten pages of response was how does this make power across the whole rev range. I don't think it does, I think it makes usable power through most of it and the rest is perceived unjustly. Bring on the dyno charts while I pop my popcorn. :-)
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post #95 of 95 Old 09-26-2019, 10:36 AM
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Join Date: Oct 2018
Location: Canada's Nortwest
Posts: 49
Years ago I bought a used 1981 Yamaha XS Eleven Special. It had amazing top end power but was weak at low RPMs and got horrible fuel mileage.
You had to be careful not to rev it past the red line. I was pretty sure someone had installed high performance cams.
I pulled the valve cover to check the valve clearance and found the intake cam was 4 teeth advanced on the sprocket creating a lot of valve overlap.
I timed the cams correctly and put the bike back together.
It was way nicer to drive the low end power was great It still had good top end power just less and the fuel mileage increased by about 50%.

Last edited by terry_g; 09-26-2019 at 01:25 PM.
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