Some major upgrade advice - Page 7 - 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 #61 of 147 Old 10-31-2019, 10:16 PM Thread Starter
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That had me laughing for a bit. Thanks, I needed that.

Truthfully, if I really had the skills Iíd put a BMW boxer motor into any motorcycle. I love the sound, the torque, and power, but mostly I just like the look. Would be terrible in a dual sport though. I can see a jug on the ground now after a rough hit.


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post #62 of 147 Old 11-01-2019, 11:25 AM
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So, Iím basing my choices on knowledge gleaned from others that have already done it. Iím just trying to put together a package from off the shelf parts as much as possible. EMís 719cc BBK, web Cams 163 grind camshaft & high performance spring kit, Schnitz Racingís SS oversize valves, and Race Tech to do the machine work.

If I can find a stroker kit or parts at an acceptable price point Iíll use that instead of EM BBK, but everything else would stay the same.



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Honestly, I think you'd be pretty happy with all that without going with a stroker set-up - I just don't see the value for what is likely a marginal difference compared to what the 719, porting/valves/cams, etc. would get you. .....OTOH if you just want to see what's possible or if it's for bragging rights, knock yourself out.

Cheers,
Dave
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post #63 of 147 Old 11-01-2019, 01:14 PM Thread Starter
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Honestly, I think you'd be pretty happy with all that without going with a stroker set-up

I do too, but Iíve also read some of the posting on the alpha stroker test runs. So I know a stroker could be better suited to the KLR. Itís also a chance to maximize the hp & torque for this engine in one shot. Why settle for less if you donít have too?

Itíll cost about $700+ for the 719cc BBK. How much more would a stroker kit cost? If I DIY it myself, will it be $1000? $1500? Or more? Iíd be willing to sink $1500 in it for a stroker kit. Iím even willing to pay more to get my crankshaft balanced as it has to be split anyway to fit a replacement rod.

For me, itís not about the bragging rights. Others have already done it. Itís about a cost efficiency curve. There is a limit on that curve where Iím no longer willing, but itís probably more down that curve than most. I see this as a one time opportunity.


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post #64 of 147 Old 11-01-2019, 01:30 PM
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I do too, but Iíve also read some of the posting on the alpha stroker test runs. So I know a stroker could be better suited to the KLR. Itís also a chance to maximize the hp & torque for this engine in one shot. Why settle for less if you donít have too?

Itíll cost about $700+ for the 719cc BBK. How much more would a stroker kit cost? If I DIY it myself, will it be $1000? $1500? Or more? Iíd be willing to sink $1500 in it for a stroker kit. Iím even willing to pay more to get my crankshaft balanced as it has to be split anyway to fit a replacement rod.

For me, itís not about the bragging rights. Others have already done it. Itís about a cost efficiency curve. There is a limit on that curve where Iím no longer willing, but itís probably more down that curve than most. I see this as a one time opportunity.


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Only you can do the value calc for you. If (for example) you can get to 55hp for $2k (BB kit, machining, headwork, valves, cams, etc.) and it cost another $2k for the stroker (custom 1 off piston, crank/machine work, case work, balancing, etc.) and you get another 7-10hp it wouldn't be worth it to ME. How much of a displacement increase do you expect to get out of a stroker? since you would do the same flow mods in either scenario, I'd expect a stroker to give you about the same percentage power increase as the displacement increase - 719 vs ???? 800cc; that'd be 12% or 6-7hp...


Dave
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post #65 of 147 Old 11-01-2019, 01:55 PM Thread Starter
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How much of a displacement increase do you expect to get out of a stroker? since you would do the same flow mods in either scenario, I'd expect a stroker to give you about the same percentage power increase as the displacement increase - 719 vs ???? 800cc; that'd be 12% or 6-7hp...

Ah, this is why I stated that itís a one time opportunity. And you are looking at it the wrong way since I have not purchase or installed a 719cc BBK yet. Iím looking at going from 651cc to about 770cc and hopefully pushing the rear wheel hp to high 50ís or better. Thatís about 55%+ more hp than stock.

If I settle for the 719cc BBK Iím not likely to upgrade it again to a stroker. I just couldnít see tossing a perfectly good piston away. Or justify the additional disassembly, machine work, and reassembly. Thatís not considering the cost and tool purchases either.

I am willing to sink in a good chunk of change though to maximize the hp & torque as a one time upgrade option. If, and itís looking like a big if, I can source a piston. Found a shop that would do it, but their minimum order is 4 pistons. So I need to keep making calls and shooting out emails. Just to see if itís feasible.



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post #66 of 147 Old 11-01-2019, 02:39 PM
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Ah, this is why I stated that itís a one time opportunity. And you are looking at it the wrong way since I have not purchase or installed a 719cc BBK yet. Iím looking at going from 651cc to about 770cc and hopefully pushing the rear wheel hp to high 50ís or better. Thatís about 55%+ more hp than stock.

If I settle for the 719cc BBK Iím not likely to upgrade it again to a stroker. I just couldnít see tossing a perfectly good piston away. Or justify the additional disassembly, machine work, and reassembly. Thatís not considering the cost and tool purchases either.

I am willing to sink in a good chunk of change though to maximize the hp & torque as a one time upgrade option. If, and itís looking like a big if, I can source a piston. Found a shop that would do it, but their minimum order is 4 pistons. So I need to keep making calls and shooting out emails. Just to see if itís feasible.



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My point is that you'll get your 55% more power with the 719 and other mods you've stated without the additional expense and PITA of doing a "one off" stroker. Honestly, given all the same other mods (head, valves, cams, exhaust, airbox, carb) I'd bet that the difference in power between the tried and true 719 BB and a 770cc stroker is less than 5hp.... so maybe 20hp with the 719 and 24hp increase with the 770??? or 55hp vs 59hp (potentially)....is it worth it? Only you can say. there is also more risk with the stroker in getting everything right, you'll have a unique set up that won't be as easy to fix if/when required and there is also the fact that perhaps the actual gain between the two options is less as you may run into a limiting bottleneck with the head, exhaust or airbox that will reduce that 7% displacement driven hp increase to something less than that.

But just because I don't see the logic, don't let that stop you. Just having a thoughtful discussions on an interesting topic.

cheers,

Dave
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post #67 of 147 Old 11-01-2019, 02:50 PM Thread Starter
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All that youíve said is true and I canít say if it will be worth it until I find out more about the potential cost involved in a one off piston. Or I just run out of time and just give in to the 719cc BBK.


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post #68 of 147 Old 11-01-2019, 04:43 PM
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I agree with Dave's suggestion to go after more horsepower by making modifications in areas other than piston stroke. You'll increase horses quicker and have a more or less tried and true modification using "standard" components.

But, I like the idea of a stroker motor because you'll increase torque and torque can easily be felt with the seat of your pants. In my mind, the KLR engine with its over square arrangement is down on torque. I miss the torque of the old long stroke British twins and singles and would like to feel a bit more torque when riding my KLR.

What's more, just because the stroker modification may not be practical in terms of increasing h.p., you just may enjoy the modification process. And sometimes tinkering on a motorcycle just feels good and doesn't need to make total sense or be practical.

Jason

Last edited by Norton 850; 11-01-2019 at 04:45 PM. Reason: added "long stroke" to British twins and singles
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post #69 of 147 Old 11-01-2019, 04:50 PM Thread Starter
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I agree with Dave's suggestion to go after more horsepower by making modifications in areas other than piston stroke. You'll increase horses quicker and have a more or less tried and true modification using "standard" components.

Those are given components in the current build. The only question is ... to stroke it it not. And that depends on getting a suitable piston.



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post #70 of 147 Old 11-01-2019, 05:46 PM
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I agree with Dave's suggestion to go after more horsepower by making modifications in areas other than piston stroke. You'll increase horses quicker and have a more or less tried and true modification using "standard" components.

But, I like the idea of a stroker motor because you'll increase torque and torque can easily be felt with the seat of your pants. In my mind, the KLR engine with its over square arrangement is down on torque. I miss the torque of the old long stroke British twins and singles and would like to feel a bit more torque when riding my KLR.

What's more, just because the stroker modification may not be practical in terms of increasing h.p., you just may enjoy the modification process. And sometimes tinkering on a motorcycle just feels good and doesn't need to make total sense or be practical.

Jason
There was an interesting article in one of the car magazines years ago (Hot Rod?) where they went to great lengths on two identical big block chevy builds of the same displacement in an effort to "myth bust" the old tale that long stroke motors made more torque and short stroke motors made more hp......I wish I could find it again but the upshot was that it made virtually no difference. In searching the net of the old article, I did come across this reference from a race engine builder on another forum I used to frequent:


As long as the valve is unshrouded in both motors of the same displacement then the power bands will be near identicle. The reason the myth came about that a big bore makes more power is because they were still unshrouding the valves as the bore grew. Once you have reached the point of completly unshrouding the bore you will see no differeance in under square and over square engines. One of the magazines did a very good test of this a while back and accounted for pretty much everything includeing rod/stroke ratio and they ran steady state HP testing to cover the lighter/heavier rotateing assemblies and never saw more than a couple HP ANYWHERE in the power curves from top to bottom. I saw another test back in the 80s when I was a kid that came up with the same results. Another good example to look to is the chevy LS2 motors, they basically have a 318 bore size but make un holy amounts of power because they figured out how to move the valves and un-shroud them.

Mathmatically speaking no mater how you arive at the displacement the same PSI will result in the same TQ at the flywheel. Yes a big bore has more surface area to push on but the longer stroke engine has more leverage on the crank and they equal the same thing in the end.



...just food for thought

Dave
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