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How do you all know what it's revving at?

Discussion in 'Technical and Troubleshooting Torque' started by I Adore Vic, Sep 23, 2006.

  1. I've noticed many here discussing 'revs' and being a newbie to bikes and not knowing much about the mechanics of them, I'm keen to learn as to how you all tell what it's revving at....ie

    (cheers biceps!)


    Somebody please tell!


  2. Some bikes have a dial gauge or digital readout called a tachometer that gives you an indication of how fast the engine is rotating.
    If you don't have this you'll have to gauge the revs by the tingling or vibrating sensations that you feel or through the sound you hear from your exhaust.
  3. You can also buy diagnostic tachometers that attach to your coil, which measures engine revs by counting how many times teh coil is fired. many more modern bikes use this principle for their tacho, some older bikes use a cable drive off teh engine.

    Regards, Andrew.
  4. G - No tacho on my bike. At the moment I'm just 'listening' to the revs....(much like tuning the guitar!)..and think I have a fair idea of what sounds 'right' for start up. I'm guessing I can tell correctly what is too high and too low and what's just right.

    Typhoon - I've a new Virago 250 and the only instrumentation on it is the speedo. Don't slap me, but what's a coil? Is the diagnostic tachometer something you keep attached to the coil whilst riding, or is it only used in the garage?


  5. You missed red-line. Thats the fun point just before valve bouncing and engine detontation.

    It's just something you will get a feel for as time goes on but heres a bit on what different levels are.

    1,000 rpm = high idle, rpm being "engine revolutions per minute"
    Idle often around 750-900 rpm, diff bikes vary. No power here.

    Red-line is maximum rpm, bikes vary but you will recognise the sound/feeling/power. Red-line is pushing parts near to the limit (do not free rev to red-line preferably)as the engine screams and has often gone past "peak power"

    Red-lines can vary from lower than 9,000 rpm to over 18,000 rpm (maybe), it all depends on the bike.

    As revs increase (in gear) you go from near no power at idle and you will feel the bike pull harder and harder as revs increase till it reaches a point it's pulling as hard as it can. Usualy this is just before the bikes red-line. This is peak power and is around 7/8th's of full red-line revs. (varies but you got the idea)

    After peak power, the bike won't pull quite as hard till red-line is reached but is still often used to so that revs are higher when the next gear is selected.

    Economical cruising speeds for engines are around 1/4 to 1/3 of max revs (red-line)

    Usualy the 1st thing you will notice going past red-line is "valve bouncing", this is where valve springs can no longer close the valves fast enough to keep up with the engine resulting in a very distinct initial "severe miss". If you continue past this point, expect valves to meet pistons with dire expensive consequences.

    Damn I need to get my bike registered, How bored am I? Aint nothing like "over-explaining" to make me feel special.
  6. Saintan said:

    Aww. If you were down my way I'd let you take me for a ride on my bike - need someone to show me what it can do :cool: Thanks for the explanation but red - lining doesn't sound like anything I'll be getting at for quite some time.... how fast would one be going to red-line it?

    As for idle, sitting in the driveway...bike started and warmed up...are you saying the rpm would be around 750 - 900?

  7. Mine idles at 1500 - 2000 rpm... that was also confirmed by my mechanic too.
  8. I discovered a redline whilst doing an enthusiatic overtaking manouevre at Winton. Twisted the throttle, lofted the front wheel, kept it pinned and then the rev-limiter kicked in: bang bang bang! and dropped the front wheel for me. Bit of a surprise! :LOL: :LOL:
  9. You may find little lines printed on the speedo indicating the maximum speed you should go within each gear, a mate who had a 250 cruiser a while back had this on there, was useful as he had no tachometer.
  10. No such luck with Viragos I'm affraid, plain old speedo and nothing more :(
    But I don't seem to have any problems, I know when to change gears just by listening!
  11. Idle is as low as you can get the revs while still running smooth generally. Thats a high idle Booga but it wouldn't suprise me on some of these lil screamers.

    But yes, idle is just ticking over fast enough to keep a reasonably smooth idle.

    Bikes generally run high profile cams and will always have a lumpy idle, (lumpy being rough)some like to idle an engine high to get a snapier response from the throttle.

    I could probably get my Z13 to idle as low as 500 rpm but that wouldn't be to healthy for it, but not altogether bad. 800 rpm is smoth idle and takeing off takes a touch of throttle to have just over 1,100 rpm.

    Noticeable power increase till 7'500 rpm then power starts dropping off till red-line at 8,000 rpm. It can see 9,000 rpm easily but the next gear will usualy pull harder.

    Again, bikes vary with speeds/red-lines in what ever gear. I doubt a lot of bikes will do 100 kph while red-lineing 1st gear but some do. (mine does just short of 100 kph 1st gear I think). I'd tend to think the norm would be about 60-80 kph in 1st gear. (if I'm fangin, I aint watchin the speedo)

    Heres a rule of thumb, if you can pop the clutch at idle and the bike dosn't stall but lights up or pops a mono then your idle is a tad to high.

    And thanks for the offer of a ride,but my daughters all that stopping me. She knows I can't afford the fine and whinges when I want to. She can't stop me from picking her up at school though : )
  12. [img:450:402:dfba26c2e9]http://www.rpmcat.com/images/FZ3301N-F42.jpg[/img:dfba26c2e9]
    you'll have something like this on your bike, but not as fancy

    1 = 1000rpm
    2 = 2000rpm, etc.

  13. Matty, some bikes dont have tacho's.
    Think about all the cruisers you pass by when you go to look sportsbikes over. They only have a speedo.
  14. Thanks for input everyone....except perhaps msim who gets a clout over the ear for his last post ;) :LOL:

    Nothing like that on the Virago MattyB.

    My owner's manual has a little about adjusting the engine idling speed...as Typhoon suggested it says to attach a diagnostic tachometer to the spark plug lead and turn the throttle stop screw until the rpm is at the specified level, which, according to the manual, is 1250-1350 rpm. After much investigation I actually know how it's done/where it's done/what all that means!

    I'm thinking that like most things it's just going to take some time and experience to get the feel/ear for it.

    But...in the meantime, does anyone know where to get a diagnostic tachometer from and roughly how much.

  15. Lots of cruisers don’t have Tacho, fuel, or temp gauges, mine doesn’t, my bike is rev limited to 6000RPM
    Most cruisers have Speedo gauges on their tanks, which means combined with the upright seating position checking your speed whilst in traffic is dangerous as you will be taking your eyes off the road for too long,
    In fact most cruiser’s ride positions are so that you cant read your gauges with your peripheral vision, you must actually move your head down and take your eyes off the road, so its safer & simpler to not to look at any gauges when riding, works for me.