Misc: Ignition Comet timing

[Chris Launders]

I have been looking at Harley ring gears and starters and wondering if the bendix hangs down below the starter motor enough that the bendix gear will mesh while the starter motor itself will clear my duel adjuster setup for the gearbox. The top lug on the gearbox might be tilted forward far enough to make room. If all I have to do is notch out the left engine plate and inner primary plate, that would be heavenly. When and if you have time, can you tell me what the diameter is of the ring gear and if you can…roughly what’s the distance between the centre of the bendix and the underside of the starter motor. Definitely no rush… just if you happen to have them on the bench at some point. Please and thank you.

Edit… I just looked at a photo of the Sportster starter and the bendix housing is a lot longer that what I thought. I need something like this one, except opposite rotation.

View attachment 61783


View attachment 61782

I've never seen a Sportster starter motor that looks like that, this is mine, and I have three, one on a Sportster, this one and just the body of one.

The bendix is 30mm diameter, the locating boss is 50mm diameter and the solenoid body outer is 35mm from the centre of the bendix.
The body is 115mm from mounting face to the end of the cover plate bolt, the ring gear is 200mm OD and 165mm ID, the ring gear is not cheap or easy to find as they are never 2nd hand.

You can get a DENSO starter similar for a Toyota Yaris etc part DSN 926, there are probably others cheaper.

With a belt drive you don't need gearbox adjustment if you set it right to begin with, I have 3 bikes with tens of thousands of miles on each and never had to adjust any of the belts, so the box can be mounted rigid and no provision for adjustment needed.

This is my Sportster starter motor, careful attention needs to be paid to where the mounting lugs and electrical connections will end up.
I bought mine off ebay, you need the 1981 and later, I paid £20 for the one with no motor, £72 and £103 for the good complete ones.

 

[Cyborg]

Thanks for the info, much appreciated. That starter in the photo if from a Honda ATV. It would probably fit, but no way to reverse the rotation.
I wonder about using a sprag clutch on the ring gear, but I might regret that. Interesting about the belt adjustment… this is my first belt drive, so assumed the tensioner was required. But…. now that you mention it, they use belts in unit construction engines.

 

[erik]

I would kick the comet first with the help of the decompression so that the ignition knows the way of rotation! Then it should be safe to kick it into life. Erik

 

[Cyborg]

I would kick the comet first with the help of the decompression ,so that the igniton knows the way of rotation ! Then it should be save to kick it into live. Erik

I eventually figured that out after I discovered how the ignition system works, but it’s surprising how many times the engine still rolls back a bit. The only way to be sure is to have the primary cover off and watch the belt. With the height of the gearbox, the length of my legs combined with being on the wrong side of 70…. an electric starter is probably the path of least resistance.

 

[oexing]

Honestly I´d hate to have an ignition which is programmable. The thing about having some crank rotation for the blackbox to get an idea about TDC is obviously common on many such boxes. So even when no rolling back of crank has happened you need minimum one rotation for teach-in of blackbox - no one-kick-affair then.
I love my ATD paired with a small contactless infrared ignition so I KNOW what it does. But definitely no drive gear Lucas type ATD here, a small device on the breaker end - like in civilized countries .
For Lucas mag alternatives I´d probably go for distributor type ignition, some electronics in there for option. Even more so at 70 plus age . . .

Vic