Safe downshift suggestions? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 27 (permalink) Old 12-31-2007, 12:33 AM Thread Starter
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Safe downshift suggestions?

First of all, not as an excuse, it's been 35 years since I last rode a MC (a 305 Yami), so I've been practicing on the 750 I bought at the end of August and started rideing at the end of Sept. I've logged 1300 miles since then, and felt like it was starting to come back to me until today. As I was heading home on a 2 lane country road, it started to rain. I was doing about 55 mph, and as I approached my left hand turn (the light was green and there was no oncoming traffic) I braked and downshifted from 5th to 3rd. Upon dropping into 3rd, the rear kicked out, and the bike started to slide just as I was making the turn. In order to keep vertical, I had to go off the road onto dirt and wet leaves, which really got interesting. Long story short, I managed to get the bike back onto the road, and proceeded home. Obviously my mistake was approaching my left turn too fast, especially in the wet. As I am adjusting to a shaft drive (not that a chain drive would have acted differently) I'm wondering how the experienced riders in here approach their turns from these speeds. I appreciate any/all advice that keeps me on the north side of the sod! Thank you in advance....

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post #2 of 27 (permalink) Old 12-31-2007, 12:39 AM
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I think you would have been better to not shift down 2 gears.
Hard to say not being there but I would not have done that, it is better to go straight through and turn around then go down.
Good for you to not dump the bike, I bet you had a big pucker moment, had to pull the seat out of your, well you know where.

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post #3 of 27 (permalink) Old 12-31-2007, 09:51 AM
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Yep, two gears is one too many. And I guess some folks don't recommend downshifting at all to slow the bike because that change in momentum can do some funny things to the machine. Glad you kept it upright!

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post #4 of 27 (permalink) Old 12-31-2007, 10:07 AM
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First - congrats on staying upright - once a bike starts going sideways, funny things can happen and ya can easily go down in a slide, or worse have the tires re-catch at the worst possible moment and have a highside.

Second, downshift one gear at a time, ideally with a bit of a rev as you're downshifting to minimize the momentum change. I'd definitely recommend practicing straight braking and downshifting to get used to how the bike reacts.

Might be a good idea to take a MSF course (I keep hearing myself recommending this yet haven't signed up for another yet) to learn/ refresh some techniques that'll help keep the rubber side down.

Make sure to have your speed down to what ya want to enter a turn at a ways BEFORE you enter the turn - you should brake/downshift before the turn, accelerate through the turn - which is one of the main techniques they teach ya in a MSF course. I don't remember the physics behind it but essentially, accelerating through the turn helps ya keep upright.

Grr... gotta take the car today since there's ice on the road... stupid side of me still wants to take the bike... but the part of me that's went sliding on the asphalt before is talking louder than that side...

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post #5 of 27 (permalink) Old 12-31-2007, 11:28 AM
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I think a chain drive would have acted differently. This effect is caused by excessive torque in the drive shaft due to a sudden increase in its revs.
I am told that if you downshift at too high revs on a Vmax it can cause you to lose control of the back wheel and it sounds like you achieved something similar by going down 2 gears in close succession.
Personally I question the wisdom of being in 5th gear at 55 anyway. I know the conventional wisdom is that the lower the revs the less wear on the engine, but there comes a point where you are creating an unnecessarily large load because the engine is too highly geared - and this increases the wear, not reduces it. I am sometimes in two minds whether or not to change up to 5th gear at 70 - the engine is quite happy there in 4th and you won't damage it.
You must have known the engine was far to unresponsive to execute your manouevre which is why you dropped 2 gears at once. And if it felt OK in third then you were going far too fast - even if it had been dry. Can you imagine what might have happened if you had been turning right. I suggest for a manouevre like that you should have shifted into second gear. This means you should have anticipated your move much earlier and started changing down through the gears smoothly getting the benefit of engine braking as you go along. In second gear you have a responsive engine that will pick up easily and one day you may need that. If someone has told you that low revs are good and high revs are bad then they have over-simplified it.

Last edited by Simon; 12-31-2007 at 11:50 AM.
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post #6 of 27 (permalink) Old 12-31-2007, 03:18 PM
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Simon wrote [I question the wisdom of being in 5th gear at 55 anyway.]
I wondered why I seem to be getting better gas milage than most...lol...
Have a good one...Old Dog...
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post #7 of 27 (permalink) Old 12-31-2007, 04:55 PM
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Looks like you did a few things wrong here, so I'll go over what I think may have been the contributing problems.
First off, I am guessing that you did not shift from 5th (twice) to 3rd as others here took your statement, but that you meant that you were in 5th, began braking and downshifting...and ended up in 3rd , meaning for at some point you were in fact riding in 4th.
What concerned me was your statement- "Upon dropping into 3rd, the rear kicked out, and the bike started to slide just as I was making the turn."
This sounds like you either downshifted at the begining of the turn, or a nano second before you initiated the turn...both not a good idea under any circumstances.
All braking and downshifting should ideally be done before a turn, and as mentioned you then should "power" through the turn keeping the throttle on and following a smooth arc.
Braking or downshifting should never be done while actualy in a turn,if at all possible.
Adding to this you mention that it just started to rain. This is the worst time to be on the road , because when it just begins to rain, the water tends to sit on top of the pavement and it's as slippery as ice on teflon. After it rains a for a bit, the water washes off the grime and oil left by cars, and gets absorbed into the road surface some, creating a better "bond" with any water sitting on top of it.
So the jist here is you should have slowed way the hell down to ride on this, and as they say "not make any sudden movements".
The Vulcan is not a sport bike, and partly due to the shaft drive, but mostly due to the fact that it has alot of engine mass moving , it is very easy to downshift and break the rear tire loose. Many times I have simply downshifted too aggressively (read that as "too soon") and "chirped" the rear tire. Not a problem while going straight on a dry road, but a real bad thing while turning on wet pavement.
As for the comment of you being in 5th gear at 55mph...sorry, but running at higher revs while on wet roads is not what you want to do anyway....and you can safely go 40mph in 5th gear on the vulcan. Most large Vtwins have alot of torque at lower engine speeds, and are quite happy thumping along in higher gears at low engine speeds. The thing of importance here is if you grab alot of throttle while doing this, the bike will take awhile to respond..which is exactly what you want when the roads are slick..no sudden movements. If you were in a lower gear, you would accellerate quicker..and thus risk breaking the tire free.
I am also thinking that although you did "brake and downshift" that you were still going too fast for the turn. On wet roads , making left and right turns through intersections usualy has me going slow enough that I am NOT countersteering throught the turn, but actualy driving through it like a car, with very little lean. Add the fact that you may have to ride over painted sections of road , that oil leaks from cars/trucks are at their worst at intersections and that most accidents happen while making a left turn or and oncoming car is turning left...then you'd almost think you'd be safer getting off the bike and pushing it ...so going slow becomes a question of "how slow can you go?"
I'm glad you managed to ride through it all and not get hurt or spill...shows you have the chops on riding buired in your head, you just need to brush up some. Go out to a empty parking lot and practice your downshifts...mostly so you can learn the highest...and lowest...engine speeds and to get a feel how much each effects braking.

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post #8 of 27 (permalink) Old 12-31-2007, 05:39 PM
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I ussually use my braking system to slow the bike down. On occation I down shift through the gears to slow down. I do not use the down shift method to slow down on wet roads. Also I am very cautious on turns and curves when the road is wet.

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post #9 of 27 (permalink) Old 12-31-2007, 06:58 PM
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Isn't the 305 a Big Bear 2 Stroke?
Our VN's are 10.5 to 1 compression V-Twin 4 stroke.

If my guess is correct (2 stoke vs 4), the riding style between the two bikes is vastly different when downshifting into a corner wet or dry. The two stroke doesn't have nearly as much compression braking power as our VN's so you can get into a pickle real quick if not prepared for it.

I felt it for real when riding a buddies GT750 full dresser (anyone know what that beast is?).

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post #10 of 27 (permalink) Old 01-01-2008, 06:43 PM
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i prefer to engine break as much as i can so i guess i could see going down 2 gears at once before the turn (on the Vulcan of course). to me it sounds like the the problem you experienced was mostly due to less then smooth "roll off"-> "roll on" transition together with not very precise clutch rather then being in 3 gear (IMO perfect gear for faster left turn). coupled together with less then perfect surface and traction conditions it got you there.
in either case it looks like you didn't go into shock and managed to get yourself out - good job!

usually i try to complete all the gear and throttle transitions before i get into the turn. this way when i start to lean the suspension is already settled, throttle is stable and all i need to do is just roll on it more and more as i complete the turn. do i always manage to successfully accomplish this? mmm... nope. but i try.

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