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Author: Subject: Spinning a BEC and Going Backwards...
scootz

posted on 15/8/17 at 07:03 PM Reply With Quote
Spinning a BEC and Going Backwards...

Was thinking of mounting a (cable) hand clutch on my BEC shift-lever, but then I thought that this might present a bit of a challenge if I spun the car and started going backwards (would probably want to keep both hands on the wheel for as long as possible... and might not get to that clutch in time to save the engine from damage).

Or are there any systems on the market that sense you are about to go backwards and will disengage the drive for you?

Cheers





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BenB

posted on 15/8/17 at 07:19 PM Reply With Quote
Is it necessary? I spun my ST1100 BEC at the North Wield track day a number of times. Sat for a few seconds to get my stuff together then fired up first time.....
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ReMan

posted on 15/8/17 at 07:43 PM Reply With Quote
There's an expensive mod for this on Hayabsa, to avoid starter AND engine damage in this event.
I'm guessing it's a one way clutch/bearing in the starter to engine link
Maybe a possible mod on your engine?





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CosKev3

posted on 15/8/17 at 08:24 PM Reply With Quote
quote:
Originally posted by BenB
Is it necessary? I spun my ST1100 BEC at the North Wield track day a number of times. Sat for a few seconds to get my stuff together then fired up first time.....


Yeah but did you get your foot on the clutch before the engine was driven backwards by the wheels?

If so that's why it did no damage! !!!

You can spin as many times as you want if you get your foot on the clutch fast enough.

A m8 of mine sold a Jedi single seater with a Gsxr1000 engine in it to someone that had never had a BEC before,went through 5 starter motors on his first drive of the car due to not clutching it fast enough when spinning!

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scootz

posted on 15/8/17 at 08:29 PM Reply With Quote
Sorry - it's an 09 CBR1000RR





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gremlin1234

posted on 15/8/17 at 08:40 PM Reply With Quote
never having had a bec etc,
apparently what you want is a sprag clutch
https://en.wikipedia.org/wiki/Sprag_clutch

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phelpsa

posted on 15/8/17 at 09:19 PM Reply With Quote
quote:
Originally posted by gremlin1234
never having had a bec etc,
apparently what you want is a sprag clutch
https://en.wikipedia.org/wiki/Sprag_clutch


The sprag clutch is what causes the problem (engages in reverse). What you need is a torque limiting clutch which most modern bike engines have to avoid kickback issues . Problems mainly occurred with 99-02 busa engines which did not have one.

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CosKev3

posted on 15/8/17 at 09:37 PM Reply With Quote
quote:
Originally posted by phelpsa
quote:
Originally posted by gremlin1234
never having had a bec etc,
apparently what you want is a sprag clutch
https://en.wikipedia.org/wiki/Sprag_clutch


The sprag clutch is what causes the problem (engages in reverse). What you need is a torque limiting clutch which most modern bike engines have to avoid kickback issues . Problems mainly occurred with 99-02 busa engines which did not have one.


K5 and K6 Gsxr1000''s can't have them fitted either

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scootz

posted on 16/8/17 at 10:14 AM Reply With Quote
Cheers - is a torque limiting clutch the same as a slipper clutch?





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LBMEFM

posted on 16/8/17 at 03:12 PM Reply With Quote
Spun on occasions in my MK Indyblade at track days, as the car losses grip and goes round the natural instinct is to dip the clutch. Never been a problem for me over many years of track driving.
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scootz

posted on 16/8/17 at 04:36 PM Reply With Quote
Cheers.

Dipping the clutch would be my natural reaction as well.

Easy with a foot-clutch... but might take some getting used to with a lever-clutch on the shifter stick. And made all the more difficult with both hands staying on the wheel trying to correct the slide until the very last minute - hence why I was wondering if there were any gizmo's on the market that can help with such situations.





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deanspoors

posted on 10/10/17 at 07:18 AM Reply With Quote
How about having both? or are you wanting the clutch pedal space for your foot?

I have a busa and managed to destroy a starter after spinning my car in the wet, dipped the clutch as quick as I could too.

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motorcycle_mayhem

posted on 10/10/17 at 09:35 AM Reply With Quote
No, a slipper clutch won't help.

Engage brain, as soon as you get into a 'passenger' situation, hit the clutch pedal (or hand device). Recover car to the paddock, remove starter motor, remove end cap and wonder how something could destroy itself that badly and where all that brown dust has come from....

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coyoteboy

posted on 10/10/17 at 04:26 PM Reply With Quote
What makes this more damaging on a bec than a cec?





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CosKev3

posted on 10/10/17 at 04:33 PM Reply With Quote
quote:
Originally posted by coyoteboy
What makes this more damaging on a bec than a cec?


Pre-engaged starter motor on a bike engine doesn't like being spun at circa 10k times its normal speed!

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coyoteboy

posted on 10/10/17 at 05:38 PM Reply With Quote
Hmm preengaged starters I've seen don't automatically engage the gear in a stall or reverse scenario, and retract it after start. Only during a start (solenoid on, gear moves, starting current supplied). You learn something new every day.





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LBMEFM

posted on 10/10/17 at 06:06 PM Reply With Quote
I am surprised like coyoteboy, is that really why bike engines don't like going backwards
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CosKev3

posted on 10/10/17 at 06:13 PM Reply With Quote
Perhaps pre-engaged is the wrong word?

The starter on a bike is engaged permanently, but will only freely turn one way due to the sprag gear as mentioned above.

So when the transmission is turned the opposite way to normal running the starter is spun at a massive amount of turns more than designed due to the gearing.

So if you are lucky it just destroys the starter,but has been known on Busas iirc to destroy the engine if the starter seizes.

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adithorp

posted on 10/10/17 at 08:01 PM Reply With Quote
The starter isn't pre-engaged, it's permanently engaged via a sprag gear. Think of it like the free-wheel on a bike. Turn the starter motor and it drives the engine, once the engine starts (and the starter isn't driven the sprag gear free wheels. However turn it backwards and it forces the starter backwards... just like rolling a bike backwards forces the pedals around.
The damage is caused by the brushes getting worn from rotating in one direction and getting a slight angle on their ends. When it goes the other way they dig in and smash the com' etc to bits.

I went 7 years and quite a lot of spins before I was a bit late getting the clutch in and buggered a starter. I take a spare to track days (and tours) now.





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bg0013

posted on 10/10/17 at 11:20 PM Reply With Quote
quote:
Originally posted by scootz
Cheers.

Dipping the clutch would be my natural reaction as well.

Easy with a foot-clutch... but might take some getting used to with a lever-clutch on the shifter stick. And made all the more difficult with both hands staying on the wheel trying to correct the slide until the very last minute - hence why I was wondering if there were any gizmo's on the market that can help with such situations.


I have to do the same set up due to a license condition limiting me to an automatic vehicle (the only definition I could get out of our authorities in Australia was that an automatic vehicle only had 2 pedals).
my car will be primarily a road car, so apart from developing the technic to make it all smooth, I cant see it being an issue.
track use might be another issue when/if I spin it.

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mangogrooveworkshop

posted on 11/10/17 at 04:06 AM Reply With Quote
quote:
Originally posted by scootz
Was thinking of mounting a (cable) hand clutch on my BEC shift-lever, but then I thought that this might present a bit of a challenge if I spun the car and started going backwards (would probably want to keep both hands on the wheel for as long as possible... and might not get to that clutch in time to save the engine from damage).

Or are there any systems on the market that sense you are about to go backwards and will disengage the drive for you?

Cheers


You are worrying about something that is a no issue. stick with a foot clutch and design to KISS engineering principles
With a bike motor it tends to stall in a spin . The challenge is to get it back into the lower range of the box and restart it.
Been there done that and bought the T-shirt and changed the pants.
There is several guys who for health reasons have full hand controls in their sevens perhaps they may help you in that field

Get on and build and stop over thinking the engineering.

Yes I have that TShirt too .....with all the side symptoms

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phelpsa

posted on 11/10/17 at 06:23 PM Reply With Quote
You might not get your foot on the clutch, but you will generally keep it firmly on the brake! That is usually enough to prevent damage.
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LBMEFM

posted on 12/10/17 at 08:33 AM Reply With Quote
quote:
Originally posted by phelpsa
You might not get your foot on the clutch, but you will generally keep it firmly on the brake! That is usually enough to prevent damage.


Well done phelpsa, simple but of course the obvious thing to say i.e. wheel not turning engine not turning, brilliant.

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ReMan

posted on 12/10/17 at 10:32 AM Reply With Quote
It is obvious!
I agree that you should not over worry , else you'll never drive it
However in the heat of a few millisecond, just as your grip/skill runs out, on the track, going backwards, bouncing over the kerbs, into the infield, I lost all sense of what pedals I was pressing
And blew the starter!

Only a cheap fireblade, and only the starter damaged.
If it was Busa motor, then you'd want to take out that insurance with the mod





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