Board logo

Sprag gear for starter? Necessary?
reb - 19/7/17 at 12:25 PM

Hi,

I just discovered this product: http://www.novaracing.co.uk/ProductHayabusaStarterClutch.html

Here the description:

"The Nova Hayabusa Starter Clutch is primarily designed to protect the starter motor and gear train from damage caused by low battery power. It may also help to avoid damage in the case of an involuntary reverse caused by spinning a car. However this will be dependant on the speed and duration of the spin!!!

By introducing a slipping element into the sprag gear in the upper starter train a measure of protection is introduced."


What do you think about such a sprag gear? Can I get away without it or is it a worthwhile upgrade?

If I am not mistaken I just have to engage/press the clutch if the car is spinning to avoid damage.

So this sprag gear will only help if I dont engage/press the clutch in time or if I forget to do it?

Can also someone explain how a low battery can cause damage to the starter motor and gear train?

[Edited on 19/7/17 by reb]

minitici - 19/7/17 at 12:41 PM

With a low battery, the motor can 'kick-back' when trying to start and this can damage the starter gear.
A similar thing can happen if you try and bump start a Busa.

hkp57 - 20/7/17 at 08:35 AM

If you do spin the car on track you can damage the crank case also not just the starter, it rips the motor from the case.

cosmick - 20/7/17 at 10:08 AM

You already have a Sprag clutch in your starter system fitted standard as your engine is a Gen2. So no need to buy one.

The Suzuki factory fitted this to protect the crank and crankcase in the event that the engine backfires when starting. A low battery was the common reason for the engine firing backwards when pressing the starter button. Sometimes this could cause serious damage to the crankcases or even twist the crank at the starter end of the crankshaft. However it has a bonus that when fitted to a Kit Car, in the event that you spin the car it can help protect the starter motor from being destroyed. You have to be mighty quick to press the clutch down to prevent the starter motor from being engaged. It has caught a lot of experienced drivers out and requires a new starter motor to be fitted if no sprag clutch is used.

MikeRJ - 20/7/17 at 01:59 PM

quote:
Originally posted by cosmick
You already have a Sprag clutch in your starter system fitted standard as your engine is a Gen2. So no need to buy one.


Pretty much all modern(ish) bike engines use a sprag clutch in the starter system, including the first generation Hayabusa. The only difference is that this system introduces a torque limiting friction clutch as well.

reb - 24/7/17 at 10:45 AM

Thanks for all the replies and the detailed information.

So is this torque limiting friction clutch a wortwhile or even necessary upgrade?

The seven is used for track duty most of the time.

phelpsa - 24/7/17 at 10:59 AM

quote:
Originally posted by reb
Thanks for all the replies and the detailed information.

So is this torque limiting friction clutch a wortwhile or even necessary upgrade?

The seven is used for track duty most of the time.


This is only an upgrade on 99-02 engines. All subsequent hayabusa engines are fitted with them as standard.

motorcycle_mayhem - 24/7/17 at 11:41 AM

As above, K3 and over.

A 24V starting system is a good idea with modified engines, the more modified, the more essential it becomes.

reb - 25/7/17 at 04:39 PM

I am a bit confused now.

So the K3 and over have the sprag gear installed already from factory.

But if I understand correctly the solution of Nova Racing adds an additional slipping element into this sprag gear.

Or does the K3 and over sprag gear already has this slipping element included from factory?

phelpsa - 25/7/17 at 05:18 PM

quote:
Originally posted by reb
I am a bit confused now.

So the K3 and over have the sprag gear installed already from factory.

But if I understand correctly the solution of Nova Racing adds an additional slipping element into this sprag gear.

Or does the K3 and over sprag gear already has this slipping element included from factory?


All hayabusas have a sprag (one way) clutch. This is on the end of the crank.

K3 onwards also have a torque limiting clutch on the end of the starter and use the long nose starter.

Pre k3 engines have a solid gear on the end of the starter and use the short nose starter.

The nova inner cover is often sold as an upgrade for later engines as it provides a bit more support to the starter gear train, but the clutch arrangement on its own is no better than the Suzuki one.

reb - 26/7/17 at 09:08 AM

quote:
Originally posted by phelpsa
quote:
Originally posted by reb
I am a bit confused now.

So the K3 and over have the sprag gear installed already from factory.

But if I understand correctly the solution of Nova Racing adds an additional slipping element into this sprag gear.

Or does the K3 and over sprag gear already has this slipping element included from factory?


All hayabusas have a sprag (one way) clutch. This is on the end of the crank.

K3 onwards also have a torque limiting clutch on the end of the starter and use the long nose starter.

Pre k3 engines have a solid gear on the end of the starter and use the short nose starter.

The nova inner cover is often sold as an upgrade for later engines as it provides a bit more support to the starter gear train, but the clutch arrangement on its own is no better than the Suzuki one.


Great, thanks for the explanation.