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Thread: Scared to rev it

  1. #21
    Super Moderator longdistancerider's Avatar
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    Quote Originally Posted by BlargKing View Post
    And I don't know what you mean about the speedo going black, all I saw was a motorcycle definitely obeying the speed limit
    At 1:48 mark the speedo blacks out then reappears later.
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


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  2. #22
    Senior Member HerrDeacon's Avatar
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    He just blacked it out when editing the video to hide any incriminating evidence
    Perry

    1972 Honda CB350
    / 1978 Honda XL250S / 1982 Honda MB5 / 2017 Honda Africa Twin
    Riding Through the Fog


  3. #23
    Member BlargKing's Avatar
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    I'd hate to post anything that might be interpreted as me possibly going faster than the posted speed limit. Rather unfortunately as I accelerated, sunlight reflecting off the speedometer caused a glitch in the video
    1984 Honda CB450SC Nighthawk

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  5. #24
    Super Moderator longdistancerider's Avatar
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    With the speed limits in Canada it's difficult not to exceed them, especially if you running an MPH speedo. When I was in St. John NB I don't think I ever got past 2nd gear until I got out on 1 headed back to Maine.
    I doubt RCMP or any other law enforcement is checking forums for excess speed posts.
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


    https://www.hondatwins.net/forums/22...d-attempt.html and https://www.hondatwins.net/forums/1-...r-attempt.html
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  6. #25
    Member BlargKing's Avatar
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    Its a Km/h speedo thankfully, I think the 1984 Model year was only available in Canada, as I've noticed a lot of parts places online don't list a 1984 model, just 1983 then 1985. Pretty sure my bike originated in Quebec because all the stickers on the bike are in French. I personally will ride in 6th gear at 50 Km/h and laugh that my 35 year old bike gets better fuel economy than suckers driving a Prius
    1984 Honda CB450SC Nighthawk

  7. #26
    Sensei 66Sprint's Avatar
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    Apparently, you've missed our point.......50 kph (31 mph)is a mid-range second gear speed (maybe 7K rpm)....at worst low end third....
    LUGGING your engine in high gear at 50 kph will be as detrimental to the engine as over-revving it, just in a different manner......and, You'll likely stall.......
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."
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  8. #27
    Member BlargKing's Avatar
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    I've never stalled it in 6th gear, 2.5K rpm seems fine, its not knocking, shuddering, or otherwise complaining. I only do it on level terrain anyway, if theres a hill or I need to accelerate I drop down a couple gears first.
    1984 Honda CB450SC Nighthawk

  9. #28
    Super Moderator longdistancerider's Avatar
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    1st) Stay out of 6th gear until you're at least 50mph/80kph. 6th gear is an overdrive only gear. Also it is quite thin compared to the other 5 and as a result it's weaker and eventually you'll strip the teeth off.
    2nd) These engines need to be running over 4,000 rpm to begin the power band, actually hits @4300 if the timing is correct. To prove my point here is a dyno sheet on my CM400 which has the same exact cam as you do so zero difference with the 450. As you can also see power peaks at @8700 although that could be due to the fact that at 8K I retard the timing 1 degree, 42*, and 1 more degree at 9K, 41*. NOTE: the graph starts at 2K and each vertical line is 1,000 rpm
    Scared to rev it-dyno-results-small.jpeg.jpg

    3) Lugging an engine, operating below the power band, is very hard on the bearings, rods. pistons and crankshaft. With all the minor problems you've struggled with, to the point of thinking about dumping it, I'm sure you don't want the issue of rebuilding or replacing the engine.
    Attached Thumbnails Attached Thumbnails Scared to rev it-dyno-results.jpg   Scared to rev it-dyno-results-small.jpeg.jpg  
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


    https://www.hondatwins.net/forums/22...d-attempt.html and https://www.hondatwins.net/forums/1-...r-attempt.html
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  10. #29
    Member BlargKing's Avatar
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    Fair enough, you've presented me with the information and the reasoning behind it. I'll keep the engine in its powerband from now on. I guess I'm just used to automatic cars that are in 5th or 6th gear by the time I'm at 50-60 Km/h.
    Last edited by BlargKing; Yesterday at 04:23 PM.
    1984 Honda CB450SC Nighthawk

  11. #30
    Senior Member -alan-'s Avatar
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    Quote Originally Posted by longdistancerider View Post
    1st) Stay out of 6th gear until you're at least 50mph/80kph. 6th gear is an overdrive only gear. Also it is quite thin compared to the other 5 and as a result it's weaker and eventually you'll strip the teeth off.
    2nd) These engines need to be running over 4,000 rpm to begin the power band, actually hits @4300 if the timing is correct. To prove my point here is a dyno sheet on my CM400 which has the same exact cam as you do so zero difference with the 450. As you can also see power peaks at @8700 although that could be due to the fact that at 8K I retard the timing 1 degree, 42*, and 1 more degree at 9K, 41*. NOTE: the graph starts at 2K and each vertical line is 1,000 rpm
    Click image for larger version. 

Name:	Dyno results small.jpeg.jpg 
Views:	9 
Size:	22.3 KB 
ID:	293058

    3) Lugging an engine, operating below the power band, is very hard on the bearings, rods. pistons and crankshaft. With all the minor problems you've struggled with, to the point of thinking about dumping it, I'm sure you don't want the issue of rebuilding or replacing the engine.
    I think you're being a bit hard on the OP. It's not a hair-trigger two-stroke with a power band about 500rpm wide - it's a 4-stroke parallel twin in a fairly mild state of tune, with as flat a torque curve as I've seen in a long time. I take your point about the fragility of 6th gear - but as regards the other two points, there's no discernible 'power band' that I can see. I can't really see the axes on the graph in detail, but it looks like its making 80-90% of the peak torque from about 2k onwards - ideal for a flexible power plant that can be driven round in a relaxed manner if required

    Based on that, and my own experience of small/medium sized 4-strokes, I cannot see any reason why he shouldn't ride it sub 4000 rpm providing it's not actually labouring the engine - which he would see and feel. Or am I missing something altogether here ?

    (If I applied that same logic to my modern sports bike btw, pretty sure 3rd-6th gears would be entirely surplus to requirements on most of the roads round these parts )
    Last edited by -alan-; Yesterday at 05:48 PM.
    CB450 K5

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