685 bore vs hotcams modification - Kawasaki KLR 650 Forum
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post #1 of 10 Old 03-05-2011, 08:55 AM Thread Starter
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685 bore vs hotcams modification

Hi,
For me, the joy of owning a motorcycle is of course to ride but also to modify it by improving on years of Engineering. I love almost everything about my 09 KLR 650. I'm a big guy and I wish this machine had 8 to 10 hp more! Along with the usuall performance modifications (jetting, exhaust, air flow, thermo-bob, progressive suspension) I am seriously thinking of the 685 Kit and/or Hotcams stage 2 cams. I ride 80% road and 20% dirt...My take on these 2 modifications:

685 bore: + power all across the RPM range, + reasonnably affordable. - not a whole lot of steel left on that cylinder, - little harder to do for DIY.

Stage 2 cams: + Cheaper, + easier to do. - Power in the mid to high RPM range...I am starting to lean towards this option for this summer...

I installed performance cams in my KZ engines before...at low RPM, the bike performs almost like a stock bike, perfect for cruising. If you want to play hard, just twist that throttle and HANG ON!

I have not found a lot of threads talking about cams for the KLR...Am I missing something? Anyone with experience with these cams?
Thanks for your inputs.
Eric.
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post #2 of 10 Old 03-05-2011, 10:21 AM
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Originally Posted by ech2o2 View Post
Hi,
For me, the joy of owning a motorcycle is of course to ride but also to modify it by improving on years of Engineering. I love almost everything about my 09 KLR 650. I'm a big guy and I wish this machine had 8 to 10 hp more! Along with the usuall performance modifications (jetting, exhaust, air flow, thermo-bob, progressive suspension) I am seriously thinking of the 685 Kit and/or Hotcams stage 2 cams. I ride 80% road and 20% dirt...My take on these 2 modifications:

685 bore: + power all across the RPM range, + reasonnably affordable. - not a whole lot of steel left on that cylinder, - little harder to do for DIY.

Stage 2 cams: + Cheaper, + easier to do. - Power in the mid to high RPM range...I am starting to lean towards this option for this summer...

I installed performance cams in my KZ engines before...at low RPM, the bike performs almost like a stock bike, perfect for cruising. If you want to play hard, just twist that throttle and HANG ON!

I have not found a lot of threads talking about cams for the KLR...Am I missing something? Anyone with experience with these cams?
Thanks for your inputs.
Eric.

Patman's Dyno page is a good resource for KLR motor mods.

The general consensus seems to be that the head is the major restriction in the motor. You won't get good power increases without going to larger valves.

No eye has seen, no ear has heard, no mind has conceived what God has prepared for those who love him. 1 Cor 2:9
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post #3 of 10 Old 03-05-2011, 08:35 PM
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"No replacement for displacement."

Truer words . . . oh, you know the rest.

IMHO, "trick" cams reach their potential only when integrated as a component in a system of interactive performance modifications.

If, as Spec says, the head flow passages and valve area are the limiting factors of performance, radical cams my do little if any to enhance power output. The HP and torque peaks can be moved about, but--until the "breathing problems" are solved, little performance gain from cams alone.

Patman's charts show, if I remember correctly, the biggest bang for the buck comes from displacement increase, in the population of all modifications.

Are "before" and "after" Hot Cams horsepower-and-torque vs. rpm curves available?

My opinion/assesment only; YMMV!
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post #4 of 10 Old 03-05-2011, 10:28 PM
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I don't know anything about the hot cams, but I have stepped off of my stock 08 and directly onto a 685 08... The difference was noticeable to me on takeoff, not a huge increase, but noticeable. Seeing as most of a KLR's usage is in the low to mid RPM's I personally think the 685 kit is a better upgrade. I plan on doing the 685 kit on mine one of these days, sooner if it becomes an oil consumer . These are just my opinions and YMMV.

Cheers,
Stew

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post #5 of 10 Old 03-05-2011, 10:41 PM
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I agree with spec, you're not going to get much out of the hot cams w/o installing larger valves. The 685 is a bonified bang for your buck and you can always add the stage II head and cams later.
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post #6 of 10 Old 03-06-2011, 08:57 AM Thread Starter
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Thanks to all of you for the input.
I revisited Patman's page and I see what you mean about the 685 kit! A good hp increase across the entire rpm range and again another major increase with head work...Proving Spec's and Damocles' point. Obviously, even the 685 kit suffers from not enough air flow through the head. Porting and enlarging the valves would definitly increase the flow of air.

On MTech's website, they offer mild porting and vavle job for a resonnable amount of $. I guess that would be where the Hotcams would shine: combine with less air restriction, bigger valve and larger displacement the larger lift and longer duration provided by the new cams could bring quite a bit more air and gas into the cylinder.

I don't think Patman tried performance cams...I wonder if anyone did...he seemed to acheive a 30% power increase (@6000rpm 44vs34hp) without it. Would one have to worry also about the bottom end passed that type of power increase?
Thanks
Eric
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post #7 of 10 Old 03-06-2011, 11:12 AM
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I think the bottom end is solid enough.

Camming the KLR just seems like you're well beyond the point of diminishing returns, though. In order to get anything out of the cams you need to have done the 685 with head work. Once that is done, you get to drop another $300 so that you can move the torque/power peak around, probably losing power in one place to gain it in another.

As I have said before, the vast majority of bang-for-buck performance gains with our bikes is either free or costs 22 cents (or 22 bucks if you go the KLX needle route). The 685 is fair bang for the buck, the Stage II head probably less so. Cams are unproven by report at this time, but you're $1300 into the mods at that point, so it certainly seems to be deep into diminishing returns.

If the goal is a KLR that will roost asphalt, it would seem that the better course of action would be to figure out how to drop a Ninja unit into the KLR frame... ;^)

T

p.s. - My head, cylinder, and piston are back from M-Tech, so it's all going together today...

Tom [email protected]

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post #8 of 10 Old 03-06-2011, 11:57 AM
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p.s. - My head, cylinder, and piston are back from M-Tech, so it's all going together today...

The scene this AM, in the dark recesses of the Laboratory located at El Casa De Tom, anticipation, fueled by many hot cups of caffeinated beverage:


******
ďmany a trip continues long after movement in time and space have ceasedĒ- Steinbeck, [I]"Travels with Charlie"
[/I]
[IMG]http://i718.photobucket.com/albums/ww187/vatrader01/KLR%20mechanical/04e28c5e.jpg[/IMG]

[FONT="Century Gothic"][I]Sometimes your only available transportation is a leap of faith[/I] [/FONT]
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post #9 of 10 Old 03-06-2011, 01:16 PM
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The scene this AM, in the dark recesses of the Laboratory located at El Casa De Tom, anticipation, fueled by many hot cups of caffeinated beverage:

Wile E Tom! Take lots of pics please Tom, so's I have a reference when I do mine

Cheers,
Stew

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post #10 of 10 Old 03-06-2011, 02:33 PM
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Originally Posted by Tom Schmitz View Post
If the goal is a KLR that will roost asphalt, it would seem that the better course of action would be to figure out how to drop a Ninja unit into the KLR frame... ;^)
You're going to start working on this after the 685, right? Right?!?!

Good luck with the 685 homey.




"In a car you're always in a compartment, and because you're used to it you don't realize that through that car window everything you see is just more TV." R. Pirsig

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