1973 Honda CB350 - how much power?

Discussion in 'Motorbike Technical Discussion' started by Ig, Mar 13, 2007.

  1. Ig

    Ig Guest

    Greetings. I have a general question and very much grateful for any
    I have recently moved from the flat midwest to the hilly san francisco
    I found a beautiful deal on a 73 Honda cb350... I realize that these
    engines need constant tinkering. that is not the problem, this one has
    low milage and lots of life still left.
    My question is whether a 350 engine can generate enough juice to be
    more than just a recreational bike. I would love to become the owner
    of this if it can actually be expected to climb some hills (and even
    carry a pasenger). Is this just wishful thinking?
    Back in chicago i was riding a 76 CB750.. Not looking for lots of of
    power necessarily, just functionality. what do you think?
    Thanks in advance.
    Ig, Mar 13, 2007
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  2. Ig

    Ian Singer Guest

    In 1968 I had a CB160 that was 16HP. It was big enough for the freeways
    and I drove from California to Alabama with no problems, and it was no
    problem full throttle all day. The only problem was when I had it bored
    to 175cc and the shop that installed the high compression cam left the
    original valves springs in, as well as adding the new ones, so the
    rocker arms chewed the cams up.

    Now my Honda 50 was a different matter as it always slowed climbing
    hills. On the 160 though I used to try for double the speed limit, plus
    5 and I never could quite get it to 75MPH before I had to brake.

    Ian Singer


    See my homepage at http://www.iansinger.com
    hosted on http://www.1and1.com/?k_id=10623894
    All genealogy is stored in TMG from http://www.whollygenes.com
    Charts and searching using TNG from http://www.tngsitebuilding.com
    I am near Toronto Canada, can I tell where you are from your reply?
    Ian Singer, Mar 13, 2007
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  3. No
    The Older Gentleman, Mar 13, 2007
  4. *Shrug*. I dunno. Given US sped limits, if you cruise it at 65mph it
    should be fine.
    The Older Gentleman, Mar 13, 2007
  5. <VVVBG>
    The Older Gentleman, Mar 13, 2007
  6. Ig

    Ig Guest

    Thank you all for your feedback. Sounds like it's more than just a
    scooter !
    Ig, Mar 14, 2007
  7. Just my recollection of my CB360 from that time.[/QUOTE]

    I've owned a couple of the early '70s CL360s and, after a bit of
    tinkering[1], could get them up past 120mph. Carrying a passenger was
    never a problem either...but, I only weigh about 140lbs and it doesn't
    take too many horses to pull my bean-pole bod down the road.
    (Unfortunately, even at that light weight they don't fly very well, even
    at 120+mph, after leaving said road on a banked curve. They aren't much
    good for riding on afterward, either.)

    [1]The tinkering was mostly just fine-tuning the motor and changing the
    rear sprocket and the chain.
    Zaphod Beeblebrock, Mar 14, 2007
  8. Blimey. To get a 360 to that sort of speed would need booster rckets,
    I'd have thought.

    I've alway liked the style of the CL series. Shame we never got them
    in the UK, although there are quite a few that have been re-imported
    from the States.
    chateau.murray, Mar 14, 2007
  9. Ig

    Mark Olson Guest

    This sounds suspiciously like the guy who claimed he got his stock CB900C
    to 160 mph just by carefully tweaking the carbs. When a couple of people
    told him he was dreaming he got a bit upset.

    Mark Olson, Mar 14, 2007
  10. Heh. Yes, exactly the same. My old CB360 would do about 95+ indicated,
    flat out. To get one to do a genuine 120mph would require serious deep
    surgery. And a tuned speedometer as well. The old SOHC 750s would just
    about hit 120 on a good day, but most of the time 110-115 was your
    lot. No way would a 360 twin get anywhere near that speed.
    chateau.murray, Mar 14, 2007
  11. Ig

    MadDogR75 Guest

    More than 'just a recreational bike`? Thats all the 350 was.
    Two up on Frisco hills? - It'll get you there, even with a passenger,
    but you'll have to do some fancy clutchwork & shifting.
    If you're coming off a 750, you probably won't enjoy it, and if
    over 5' 9" or so, you might feel folded kinda small.

    O.T. That coast highway is a ride not to be missed, you luck dog you.

    MadDogR75, Mar 14, 2007

  12. If you will think about it rationally for a moment gentlemen, before
    simply *assuming* that I am exaggerating, consider what I said about
    changing out the rear sprocket.

    Picture a multi-speed bicycle with different sized sprockets on the front
    and rear. Consider your legs to be the two cylinders. Pumping your legs at
    a given rate (RPM) will propel you at a given speed. If you shift the rear
    derailleur to a _smaller_ sprocket, then pumping your legs at the same
    rate as before will propel you at a *faster* speed.

    Granted, the smaller rear sprocket will change the torque(?) ratio, but at
    my relatively light body weight the sacrifice is an acceptable trade-off
    for the higher top speed.

    There is nothing magical or delusional about this:

    Smaller rear sprocket = higher top speed.

    Now, if you would like to be helpful, I wouldn't mind a little advice on
    performing a similar modification on my current machine. It is a '96
    Yamaha Virago 1100 Special which produces *far* more horsepower than is
    necessary to pull my skinny ass down the road.

    This is the first bike I've owned with a shaft-drive. I am constantly
    wishing it had a sixth gear in it. I'm not as much as a speed-freak as I
    was when I was younger, I'd just like to lower the RPM for cruising and
    improve the fuel milage...especially since it seems like the alcohol mix
    I'm getting for fuel now has put a drastic hit on it. I used to be able to
    get 165-170 miles before the low-fuel light would come on, I ran dry the
    other day at 136mi.

    I experienced the same phenomenon on a trip to Texas last year. Straight
    regular gas gave me the expected milage, the alcohol mix reduced it,
    requiring more frequent fuel stops.

    I have my doubts about the feasibility of changing the gearing where the
    shaft meets the rear axle, which means that I'd probably have to change
    the transmission gears. Is either one of these ideas feasible, without
    going to extreme effort or expense?
    Zaphod Beeblebrock, Mar 15, 2007
  13. You stupid sod.

    Have you ever thought why you sometimes need to change down a gear (or
    two) on any vehicle, when (for example) climbing a hill?

    It's because you don't have the power to pull a taller gear.

    If simply gearing up an engine (or bicycle) was all it took to hit high
    speed, every vehicle would travel at 500mph (or more).

    Yes there is. You are delusional.
    The Older Gentleman, Mar 15, 2007
  14. Ig

    Mark Olson Guest

    I don't care what you did to the sprockets, without a dustbin
    fairing on that 360, or lots of very expensive engine work,
    you don't have an icecube's chance in hell of getting it up
    to 120 mph. There are certain basic facts that you can't weasel
    out of-- and there's always somebody on Usenet who knows far,
    far more about a subject than you or I do...
    No. The faster you go, the more power it takes to get there.
    If your engine doesn't make the raw power it takes to force
    you and your bike through the air, no amount of messing with
    gearing is going to make it faster. I learned this way back
    in 6th grade when I hit on the idea of putting a large sprocket
    on the centrifugal clutch of my doodle bug and a tiny sprocket
    on the back wheel. Doing the simple math told me I could achieve
    hundreds of miles per hour with a 5 hp Briggs and Stratton engine.
    Thankfully the laws of physics have remained intact despite my
    high hopes and it isn't going to work any better for you than it
    did for me in my long-ago thought experiment.
    How much you weigh has *nothing* to do with top speed on a level
    surface. It greatly affects acceleration, but air resistance
    dominates your eventual top speed.
    You might be able to swap in the rear end from a different bike. Other
    than that, there's no easy or cheap way to change the final drive ratio
    on most shaft drive bikes.
    Mark Olson, Mar 15, 2007

  15. *Sigh*

    I try to be polite, and what does it get me? My apologies, clearly I was
    at least partially wrong in addressing my reply to "gentlemen".

    Well, no shit, Sherlock.

    Perhaps you misses the part where I addressed the trade-off in torque
    ratio. Pull your head out of your ass, the lack of oxygen is killing your
    brain cells.
    Zaphod Beeblebrock, Mar 15, 2007
  16. Ig

    Mark Olson Guest

    No, Zaphod, even allowing for your two heads, I doubt there's more
    than an ounce of so of gray matter in total, if that. Stop digging,
    you're in a hole, and you're just making yourself look *utterly*
    Mark Olson, Mar 15, 2007

  17. Actually, it does. With a lighter load and less torque required for
    acceleration, more of the engine's horsepower can be used for overcoming
    wind resistance, etc. The less available horsepower you have, the bigger
    the difference.

    Take your 5 horse B&S motor, take two of them actually, and build two
    identical go-karts. Put me on one and a 300lb guy on the other and we do
    10 laps around a quarter mile track. Who do you think is going to win the

    Granted, in this case wind resistance isn't much of an issue because the
    top speed doesn't get high enough for it to matter much. But, put 12"
    tires on those carts instead of 10" tires (we'll change tire size since it
    accomplishes basically the same thing as changing the gear ratio) and what

    If we do another 10 laps, I'm going to win by an even bigger
    margin...assuming that my opponent can get moving at all.

    Now take me and that same 300lb guy and put us both on identical stock
    CL360s...I'm guessing that they might put out about, oh, 24 horses? We run
    a straight 10 mile stretch of level highway- I'm faster off the line
    because I have less load to accelerate, it requires less energy to
    maintain my momentum AND, because I'm skinny and he's fat, *he* needs more
    energy to overcome wind resistance than I do, which becomes an increasing
    factor as speeds increase.

    Now take those same machines and change out the rear sprockets for
    sprockets with six fewer teeth. What's going to happen? Acceleration
    becomes a greater factor, but more for him than for me. With a lighter
    load and less wind resistance I'm going to beat him by an even bigger
    margin. The change in gear ratio doesn't affect me as much as it affects
    him because of his greater weight and larger size.

    Give him back his larger sprocket and set us off again- I'll bet I'm still
    faster off the line AND, because I have the taller gearing and less wind
    resistance I'm going to go a LOT faster than he is.

    On the other hand, if you were to put us both on bikes powered by 454 Olds
    Rocket motors, my size and weight wouldn't mean diddly because of all the
    excess horsepower available. With limited horsepower size and weight can
    matter more.

    Thanks, I had a feeling that might be the answer I was going to get.
    Zaphod Beeblebrock, Mar 15, 2007
  18. Ig

    Ian Singer Guest

    OK so based on what you are saying how fast should a CB160 be able to go
    with a full windshield and no fairing? Driver wearing 3/4 helmet with a
    curved molded bubble and not flat on the tank.

    Ian Singer


    See my homepage at http://www.iansinger.com
    hosted on http://www.1and1.com/?k_id=10623894
    All genealogy is stored in TMG from http://www.whollygenes.com
    Charts and searching using TNG from http://www.tngsitebuilding.com
    I am near Toronto Canada, can I tell where you are from your reply?
    Ian Singer, Mar 15, 2007
  19. OK, one more time. If you go back to my original post, you will see that I
    DID NOT say it was a "stock" CL360.

    I changed out the rear sprocket for a smaller one, sacrificing some
    acceleration/torque(?) on the low end in exchange for a higher top speed.
    Changing the rear sprocket changes the gear ratio.

    My reference to my weight was primarily an indication that I could afford
    that sacrifice.

    Does it make more sense now?
    Zaphod Beeblebrock, Mar 16, 2007
  20. I *was* trying to be polite, even in the face of
    almost-but-not-quite being called a liar. It was the "You stupid sod" part
    that kind of got my dander up. If that wasn't intended to be mean, then
    perhaps I just took it the wrong way.

    OK, I'll take your word for it and refrain from any further hostility. I'm
    sure glad that I didn't send what I had written when I *first* started to

    True enough on the fit. I've rather long legs and usually rode far back on
    the seat. With a chick on the back it was quite uncomfortable. I have the
    same problem, even on my Virago, and with the step seat it really isn't
    conducive to sliding my butt backward for a better fit.
    Zaphod Beeblebrock, Mar 16, 2007
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