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Fish tailing when engine braking

Discussion in 'New Riders and Riding Tips' at netrider.net.au started by walkinshaw, Dec 5, 2014.

  1. Hi all, I'm a new rider with about 6 months experience. My first bike was a KTM 450 dual sport, and I just recently bought a Honda rvf400. While riding it yesterday I revved it high to quite a high speed in first gear(to see how tall it was) then let off the throttle and as the bike engine braked the back wheel momentarily lost traction.

    Now I know if you dump to too low a gear for your speed the rear wheel will start to slide, but I have not heard of this happening simply by letting off the throttle in the same gear. Is this something I need to watch out for on a high rev bike? Rvf400 red lines at around 18k


     
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  2. Well, yeah, in low gears the engine braking is magnified. Shouldn't be a problem in higher gears where you'll usually be riding.
     
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  3. But are you saying you shouldn't ever rev up in to high rev ranges in first gear?
     
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  4. walkinshawwalkinshaw Yes this can happen when you shut off the throttle suddenly like this. The engine starts engine breaking hard and the effect of this is transferred through to the back wheel. The effect of slowing down also takes some weight off the back wheel which can cause the back wheel to wander or lock up.

    This is a good thing to learn, now you know why it is never advisable to close the throttle mid corner ;-)
     
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    • Like Like x 1
  5. Well assuming you can control the wheelie, you're usually only revving up high in 1st to then change into 2nd. So You're never off the throttle in 1st, so you don't have the compression lock up problem.

    If you're after low speed maneuvering, you'd be better off a low revs in 2nd with back brake and slipping clutch if required.

    More experienced riders can add more value, hang around until they respond.
     
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  6. Unless I have what happened to you wrong,you have just described why lots of sports bikes have a Slipper Clutch as standard these days.This effect is magnified in engines with a high compression ratio.When you see a road race bike sideways heading to the apex of a corner,slipper clutches make this easier to control.The effect is less abrupt and in some cases the effect can be adjusted to suit.They soften the effect of engine braking.Its doable without a slipper but is abrupt and easier to loose grip.
     
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  7. I find it extremely hard to believe that you can compression lock RVF400 (in normal conditions) by rolling off the throttle, or even chopping while always being in 1st gear.

    So you better provide more and better details before everyone will start coming up with some imaginable nonsense.
     
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  8. I cannot understand why anyone would rev the tits off theor bike in 1st then just let go of the throttle and not even gear up so the revs drop down and its not so abrupt on the bike. I cant say i have ever done this
     
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  9. Separate topic. The OP was just "curious" and there's no problem with that.

    Also if you'll have something like CBR250RR you will HAVE to the rev tits of it because that's where it's all power is.

    I rev my bike on the track to the limiter, because I need to get the most out of it.
    Bikes ARE designed to rev.

    The fact that you do not understand why anyone would rev their bike doesn't mean the bikes shouldn't be rev-d.
     
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  10. Not sure what more details you are looking for..

    It was my first proper time on the bike, just in backstreets, I was in first gear and revved high (why? I was curious, I wanted to hear the engine without doing 100kmh). After revving high I let go of the throttle and felt the bike briefly lose rear traction as the engine braking slowed it down.
     
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  11. Well, you would struggle to compression lock the rear let off the throttle in the most torquey bikes. Thus I find it hard to believe, for RVF400.

    How do you know you actually lost traction?

    I would be very keen to see what you did if you could reproduce it in from of me (genuinely).
     
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  12. I think the RVF400's have an early version slipper clutch. Maybe the slip in the clutch is what your noticing?
     
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  13. Try the same thing again, see if u get the same result. Might just be a one off due to road surface or something. I can't imagine any bike would compression lock from backing off the throttle
     
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  14. In theory you can, when you engine break you are essentially creating a vacuum within the engine due to the restricting of airflow through the engine. Now if you shut of the throttle from fully open to closed instantly you can set up a "shock" as the engine has to compensate with this restricted airflow in a very short period of time. Something like when you shut a tap closed fast on some old plumbing you get the tap shaking from the water hammer. Similar idea. This is my theory anyway.
     
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  15. If you would re-read my post you would hopefully understand that i was refering to revving it to the limiter theb backing off without changing up. On the track, that a different kettle of fish to on the road.
     
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  16. walkinshaw, don't worry about negative responses on this forum, you'll get it a lot when asking innocent questions about what you experienced on your bike. Please do what you did again, maybe on a different road with a good surface, just for comparison. Then let us know if it all went down the same.
     
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  17. All of the thumpers I had would do it in 1st or 2nd if the road was wet, occasionally 3rd if the road was particularly slick, and would drag a lot of gravel on unsurfaced roads. Mud? well dual purpose tyres slide easily Dry bitumen road? Maybe. It (engine braking) is a reason, among several, why they were fairly hard on rear tyres. My Bandit will do it on a wet road in 1st or 2nd. Never noticed it in the dry, but it gets loose on gravel.

    Slipper clutches can complicate the sensation. Wheel slip due to engine braking is more likely with light bike weight, large piston size and high compression.
     
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  18. I'm all for seeing what the bike does when you do certain things. Try it again with warm tyres and it may not actually lock up.
     
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  19. Yeah, I get it a lot with my 390 Duke, can only imagine on larger capacity thumpers.
     
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