A Question of Horsepower - Kawasaki KLR 650 Forum
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Old 07-28-2019, 05:08 PM Thread Starter
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A Question of Horsepower

Years ago I rode a Honda CB350 which produced low to mid-30's HP. Why does a KLR650 with an additional 300 cc's produce about the same HP?
I'm sure this is a stupid question, but it's the only kind I've got.
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Old 07-28-2019, 07:44 PM
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I'm pretty certain that your CB350 was a twin cylinder, correct?
One would expect a twin to have higher HP and a higher Red-Line, but with less over-all torque and possibly even a spike in both of its HP & Torque curves when plotted on a graph , compared to the 300cc larger single cylinder.

Part of it is the state of tuning for the engines intended purposes. Regardless of single vs twin cylinder design.
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Old 07-29-2019, 02:34 PM Thread Starter
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I think you are correct on all counts. It just seemed wrong at first but torque is key.
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Old 07-29-2019, 04:53 PM
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Besides an extra cylinder, your CB350 had higher compression, probably larger-area valves (than a KLR650), a camshaft with higher lift/duration/overlap than the KLR's, and . . . quite possibly, a 180-degree crankshaft (insuring a constant air-volume crankcase, not pumping in and out whole displacement with each crankshaft revolution, as does a single-cylinder engine). Add to that, the higher rpm (as pdwestman says). So . . . the CB350 can process more fuel per unit time than a KLR650, cc of displacement to cc of displacement.

Not that a single can't develop horsepower; KTM690 (with only 690 cc displacement) produces nearly 70 maximum horsepower (maybe, measured at the crankshaft, not the rear wheel).

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Old 07-30-2019, 11:31 AM
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My son's ZX6R produces 123hp from 15 less cc's ....but it peaks at 14,000 rpm. All that to say that the engine's design and design goals play a bigger part than the displacement does.

Sure the KLR isn't a hp leader, but it is torquey, runs on crap fuel and can last forever.

Dave
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Old Yesterday, 05:28 AM
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Since I bought my '08 KLR new it gets parked next to my 1972 Honda CL350 which currently has 6k miles. The engine is essentially identical to the CB350, displacing 325cc.

The Honda is remarkable for a 1968 design but its character is very different from a KLR. The power starts at 4000 RPM and the quoted HP peak is somewhere closer to 9000 RPM. As tough as it was in its day that engine can't touch the durability of the KLR engine. They were prone to cam bearing seizure and by 20,000 miles usually needed a top end refresh.

The KLR is more like a lawn tractor and I mean that in the best way possible. It's torque that gets you where you're going, not horsepower.
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Old Yesterday, 10:00 AM
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Quote:
Originally Posted by electroken View Post
Since I bought my '08 KLR new it gets parked next to my 1972 Honda CL350 which currently has 6k miles. The engine is essentially identical to the CB350, displacing 325cc.

The Honda is remarkable for a 1968 design but its character is very different from a KLR. The power starts at 4000 RPM and the quoted HP peak is somewhere closer to 9000 RPM. As tough as it was in its day that engine can't touch the durability of the KLR engine. They were prone to cam bearing seizure and by 20,000 miles usually needed a top end refresh.

The KLR is more like a lawn tractor and I mean that in the best way possible. It's torque that gets you where you're going, not horsepower.
Did the CB / CL 350 engines have an external oil pipe feeding the camshafts? If so, maybe their banjo bolt oil feed holes were too small.

It is still a small miracle to me and others how my 1987 KLR650 cams & transmission managed to survive with the already very small 1st oil feed hole restricted to about 1/2!

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Old Yesterday, 12:16 PM
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Quote:
Originally Posted by pdwestman View Post
Did the CB / CL 350 engines have an external oil pipe feeding the camshafts? If so, maybe their banjo bolt oil feed holes were too small.

It is still a small miracle to me and others how my 1987 KLR650 cams & transmission managed to survive with the already very small 1st oil feed hole restricted to about 1/2!
The CB/CL/SL350 oil passages are all internal. The Achilles heel of the engine is the archaic piston and check ball oil pump which is driven off of the rear of the clutch basket once per revolution. The centrifugal oil filter worked well enough except few owners knew it was there and fewer still bothered cleaning it.

We also have to keep in mind that those old engines came with fat pre-EPA jetting, a luxury the KLR never had in stock form. My KLR gets 53mpg on average. The puny 350 gets only 50.
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Old Yesterday, 12:47 PM Thread Starter
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At the time I thought I was asking a "simple" question. Further research on torque/HP has given me a headache. Thanks for all of the input...
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Old Yesterday, 01:09 PM
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My poor CB350. The rear fender was half-cracked through, the frame was cracked in at least three spots, and the pipes were Rockies (with the inserts held in place with split rings) because I had beaten the originals to death. It was ridden off-road a fair bit because back then there were 'motorcycles' which were largely divided between 'street legal' and 'dirt' bikes. The CL kinda sorta bridged the gap, but if you didn't have one you didn't stop just because the pavement ended. Not if there were fish to catch.

What killed it, though, was the cams.

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