Using the Starter Motor for Reverse
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HDF Community Team
Joined: Nov 2012
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From: USA
Using the Starter Motor for Reverse
I've been ruminating over the notion of using the starter motor to reverse the bike. If the starter motor is spun backwards, and the transmission is in gear, the bike should move backwards from the starter motor. It certainly moves forward on the starter motor readily enough.
But, there are a few things that I suspect make this unfeasable. There might be some others as well.
One is the primary chain tensioner. This is the one I suspect is effectively insurmountable. Reversing the forces will have the chain being pulled on the tensioner side, and I have my doubts about the tensioner being strong enough to survive this. I suspect the bracket would bend, and the plastic would get gouged deeply and quickly. Though maybe with a very stout tensioner it might survive the occassional reversing.
The other has to do with spinning the engine backwards. Can't get around this, if the starter motor is spinning backwards, so is the engine. So the cam drive is reversed, as is the oil pump. I can't think of anything that is automatically or inherently destructive in the backwards spinning of these components, but it is generally considered not a good idea.
I'm sure I'm not the first person to think along these lines. Though to my surprise I find little on the web about doing this.
Anyone know of attempts to do this, or have thoughts regarding difficulties I haven't considered?
But, there are a few things that I suspect make this unfeasable. There might be some others as well.
One is the primary chain tensioner. This is the one I suspect is effectively insurmountable. Reversing the forces will have the chain being pulled on the tensioner side, and I have my doubts about the tensioner being strong enough to survive this. I suspect the bracket would bend, and the plastic would get gouged deeply and quickly. Though maybe with a very stout tensioner it might survive the occassional reversing.
The other has to do with spinning the engine backwards. Can't get around this, if the starter motor is spinning backwards, so is the engine. So the cam drive is reversed, as is the oil pump. I can't think of anything that is automatically or inherently destructive in the backwards spinning of these components, but it is generally considered not a good idea.
I'm sure I'm not the first person to think along these lines. Though to my surprise I find little on the web about doing this.
Anyone know of attempts to do this, or have thoughts regarding difficulties I haven't considered?
Grand HDF Member
Joined: Jan 2012
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From: Oklahoma
As described, it can't work because of the starter clutch. The starter clutch is "one way" and the starter motor would spin freely in opposite direction if polarity were reversed with all motion stopping at the starter clutch. Also, the same switch which actually powers the starter motor is closed by the solenoid movement which forces the starter gear to engage the ring gear on the clutch basket. No solenoid movement, no power to the starter.
I have seen a reverse done on a big Kawasaki, if I remember correctly, but have no idea of the internals which made it work. It involved an engagement lever moved before energizing the starter. Perhaps it reversed the current flow and engaged an idler gear so the starter could power the transmission while spinning backwards without spinning the engine.
I have seen a reverse done on a big Kawasaki, if I remember correctly, but have no idea of the internals which made it work. It involved an engagement lever moved before energizing the starter. Perhaps it reversed the current flow and engaged an idler gear so the starter could power the transmission while spinning backwards without spinning the engine.
Road Captain
Joined: Aug 2011
Posts: 538
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From: Florida
You're correct in the observations that the engine and primary are not designed to reverse. The starter motor itself is also not. It has an internal one-way-clutch that will prevent the starter from even spinning the pinion gear in reverse. The starter motor is also made for VERY brief VERY high torque applications of power, this is not what you want for moving the bike... If youve ever accidentally tried to start a bike in gear (without clutch/1st gear safeties) you know how suddenly it jerks forward. Now imagine grandpa trying to reverse his bike with a power application like that and shooting the bike out from under him...
Road Captain
Joined: Aug 2011
Posts: 538
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From: Florida
The triglide actually has a separate motor for reverse, it does not use the starter. Its somewhere around $1000 just to replace that motor and from what it looks like its riddled with problems. Leading many owners to do reasonably priced mechanical reverse kits.
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HDF Community Team
Joined: Nov 2012
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From: USA
Well phoey on that. Had to go back and relook at the motor drawings again to finally see there really is a one-way in there. Drat. Thought it was just reduction gearing.
And I don't disagree, using this for reverse would not be subtle or gentle.
Well, it was a thought.
And I don't disagree, using this for reverse would not be subtle or gentle.
Well, it was a thought.
Road Captain
Joined: Aug 2011
Posts: 538
Likes: 3
From: Florida
If you're looking for a reverse solution I would consider a mechanical kit to do it right. Most of these kits are in the realm of $1400. Like I said in my last post, even Harley's attempt at electrical reverse with a separate motor has pages of complaints and failure reports. Some of these failures costing over $1400 to fix...
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Road Captain
Joined: Aug 2011
Posts: 538
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From: Florida
Maybe you could fit a gold wing starter on your harley, up until the 90's they had two sets of planetary gears in the starter. One for starting and one for reverse! After that they moved to a "electrically assisted reverse gear" that was in the transmission
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Joined: Apr 2010
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reverse gear is an option that the moco should offer on all its bikes. their target market is the older affluent rider...exactly the people that would appreciate and could afford the reverse gear. wrestling 900 lbs. around in tight parking places is not fun, and eventually we will become to old and feeble to do it at all. the reverse gear might increase our ability to keep riding for a few more years.