[heloego]

"btw - a solenoid does mechanical work like pushing a gear or a door, a relay makes an electrical connection"

Bingo! 

[heloego]

"I hope the quality is OK!  "

   Shouldn't be any worse than the originals.  And may just be better. 
   I could throw a lot of different ones on as replacements, but somehow they just don't seem right.

[Mick Bailey]

I hope they're better. One real problem with the originals (and I've experienced this on two different bikes) is the relay sticking on due to the terminals welding closed. Turning off the ignition won't kill the starter once this happens, as the main switching contacts are independent of the switch circuit. It's a bad situation, with the starter continually engaged (even with the engine running) and the reason I always carry an emergency spanner in my pocket to disconnect the starter terminal if it should happen again.

[elysianforest]

One real problem with the originals (and I've experienced this on two different bikes) is the relay sticking on due to the terminals welding closed.

Yipes! That's awful. A wrench in the pocket is a very good idea. I may start doing the same - though I suspect the relay on my bike is not stock. I'll have to look into that...

[Arizoni]

Not to belabor it but a electrical relay uses a solenoid to actuate the electrical contacts to open or close the switch.

 Wikipedia says this about solenoids and I agree with it:

"In engineering, the term may also refer to a variety of transducer devices that convert energy into linear motion. The term is also often used to refer to a solenoid valve, which is an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid."

https://en.wikipedia.org/wiki/Solenoid

Anyway, if the relay/solenoid is clicking but the electrical contacts are not closing or conducting power from the battery to the starter motor, the thing should be replaced.

[REpozer]

Not to belabor it but a electrical relay uses a solenoid to actuate the electrical contacts to open or close the switch.

 Wikipedia says this about solenoids and I agree with it:

"In engineering, the term may also refer to a variety of transducer devices that convert energy into linear motion. The term is also often used to refer to a solenoid valve, which is an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid."

https://en.wikipedia.org/wiki/Solenoid

Anyway, if the relay/solenoid is clicking but the electrical contacts are not closing or conducting power from the battery to the starter motor, the thing should be replaced.

True, true. That way you can use a small wire to control a heavy wire at the battery.

[elysianforest]

Not to belabor it but a electrical relay uses a solenoid to actuate the electrical contacts to open or close the switch.

 Wikipedia says this about solenoids and I agree with it:

"In engineering, the term may also refer to a variety of transducer devices that convert energy into linear motion. The term is also often used to refer to a solenoid valve, which is an integrated device containing an electromechanical solenoid which actuates either a pneumatic or hydraulic valve, or a solenoid switch, which is a specific type of relay that internally uses an electromechanical solenoid to operate an electrical switch; for example, an automobile starter solenoid, or a linear solenoid, which is an electromechanical solenoid."

https://en.wikipedia.org/wiki/Solenoid

Anyway, if the relay/solenoid is clicking but the electrical contacts are not closing or conducting power from the battery to the starter motor, the thing should be replaced.

Then we have consensus! Thank you Wikipedia! Though I will point out that the solenoid switch is just one type of electrical relay... 

[sheldogg]

I'm happy my ignorance resulted in a thorough syntactic discussion. It wasn't just me calling the electric start relay a solenoid, but I and the rest of us who were had it wrong.

Update: I got my bike started. Went to the obvious solution tonight (spark plug) and that was the source. Previous owner actually had an automobile plug (higher resistance/less noise) in there; I swapped it for a small engine plug. Went for a ride and the bleeping main fuse blew out. Again.

I noticed that my ammeter was reading lower than it had prior to my adventures in tracing starter malfunction and prior to replacing the plug. That means more amperage from the stater to the battery during operation and a higher chance of that pesky fuse being blown, correct? So...why and what to do.

I didn't replace that 2-wire connector I had yanked out. But as it's a)passive and b)connected only to the starter button from the battery why would replacing it cause an amperage spike? Could it be, rather, that I used a plug I had lying about (for use in the combustion mower I haven't used since I went electric)?

I'm leaning towards the plug, keeping in mind that I must find a suitable 2-wire connector to replace the one I yanked out. Any suggestions on the ideal plug for this bike? Google returns this result (verified by a couple of top-result threads):

https://shop.advanceautoparts.com/p/ngk-iridium-ix-spark-plug-bpr5eix-6597/15650094-p?c3ch=PLA&c3nid=15650094-P&c3apidt=21898413984&gclid=Cj0KEQjwhMjKBRDjxb31j-aesI4BEiQA7ivN-MofsTqBkqYJSsnn74TVSD8LMTFwIXqdTSEcoNnbYgIaAuVd8P8HAQ&gclsrc=aw.ds

I also found these things:

http://www.sixity.com/4pcs-royal-enfield-bullet-500-ngk-standard-spark-plugs-500-kit-set-engine.html?gdffi=b1371d1e394c41aba12c50049d024483&gdfms=C93ED21A891044EA8ACE9D65491838CC&gclid=Cj0KEQjwhMjKBRDjxb31j-aesI4BEiQA7ivN-JOVJ_4gcKexZUG8y6Tsak5toBFp9SrJa4DJbU6VQUQaAt2k8P8HAQ

https://www.ebay.com/i/272728860785?chn=ps&dispItem=1

I'm considering going up from 15a fuse to 20a fuse. Are there any perils involved? My battery rates 14a so...maybe I shouldn't?

[elysianforest]

I'm considering going up from 15a fuse to 20a fuse. Are there any perils involved? My battery rates 14a so...maybe I shouldn't?

No, you shouldn't. You can probably get away with it for a short while before stuff starts melting, but you're not solving the issue. The issue is that you have something that is drawing too many amps - very likely a short somewhere.

It's not very likely to be your little mower plug, but who knows. You should certainly begin with the right plug. I like the NGK B9ES, which I do believe is a pretty standard plug for this bike. There is a chance it can produce some radio interference that will mess with your TCI*, but you should be alright as long as you have a metal plug cap. If your cap has been replaced with a rubber one, go for the BR9ES, which has a resistor in it and will reduce the interference. The non-resistor types have a bit stronger spark since there isn't that electrical loss, but not enough to really be able to tell. The iridiums seem like a waste of moolah to me since you're probably gonna be tweaking this bike on a regular basis.

What your mower plug very likely is is too short. That means it is probably recessed in the plug hole which can cause hot spots and misfires and carbon buildup. Eww. Get it outta there!

Okay, I really gotta go to bed. Goodnight!

*Edit: TCI - not TDI. Was too late last night. I don't think there's any turbo diesel to concern yourself with!

[Mick Bailey]

The plug is not the cause of your problems. In any case, you need to have the correct plug for your engine. There are various noise suppression aspects the the HT circuit - the plug lead itself (can be copper or carbon/polymer core) the plug cap (can be resistor or non-resistor type) and the plug itself (resistor or non-resistor). Metal screening around the plug cap is in addition to any resistive element to the circuit. There is no reason to replace the stock cap unless it's giving problems. If you do, I recommend using a resistive cap (5K Ohm) with the stock NGK B9ES plug. The NGK plug caps are pretty much infallible and I've been using them since the early 80s in all kinds of weather and conditions.

Because the HT side of your coil is high-impedance, the presence of a series resistance in the lead, cap  or plug does little to diminish the spark intensity. However, it does reduce EMI which can cause mis-triggering of the TCI at higher RPM.

The starter circuit is only fused on the low-current side. On the high-current side the starter is connected directly to the battery via the starter relay and is unfused. Once the bike is running this is disconnected. A fuse blowing while you're riding is most likely to be an intermittent short somewhere, perhaps a chafed wire, but it will not be the plug that's causing this.

[tooseevee]

Update: I got my bike started. Went to the obvious solution tonight (spark plug) and that was the source. Previous owner actually had an automobile plug (higher resistance/less noise) in there; I swapped it for a small engine plug. Went for a ride and the bleeping main fuse blew out. Again.

            Get the mower plug out and you don't need an Iridium (100,000 mile) plug.

            You want a B9ES if you have the OEM resistor cap. If not, you want a BR9ES. Just find the best free shipping deal online and order some. You will need more than one plug while you are dialing in this bike.

             This is a very simple basic engine. Stick to the basics.

              Any good two-pin connector will replace the one you chopped out.

[REpozer]

Just a heads up here to newbies , you got some high end contributors here with good advice.
Honorable mention to Arizoni who no doubt is related to Dr Oldsmobile.
And 2CV , so skilled he can stop a leak with oakum and saltwater, probably could brew a Blaatz beer clone?

[Arizoni]

sheldogg said
...I'm considering going up from 15a fuse to 20a fuse. Are there any perils involved? My battery rates 14a so...maybe I shouldn't?

Your confusing maximum amperage output with Amp/Hour ratings.

The 14 AH (amp hour) rating is the amount of power the fully charged can deliver in the period of one hour before it's run down.

The battery is fully capable of delivering over 60 amps for short periods of time.  In fact, your starter motor draws over 50 amps of power while it is running.

For a very short period of time I wouldn't be surprised to find the battery is totally capable of delivering over 100 amps of power.  Even if it can't, it is totally capable of melting your entire wiring harness if a short occurs.

[tooseevee]

For a very short period of time I wouldn't be surprised to find the battery is totally capable of delivering over 100 amps of power.  Even if it can't, it is totally capable of melting your entire wiring harness if a short occurs.

            Drop a wrench across your (not you; anybody) battery's terminals and it'll show you how powerful it is in glorious high def living color

             I did it once in the '60s on a 24V boat battery that weighed almost as much as I do. (I weighed the same then as now). 

[Mick Bailey]

Not so common with bike batteries, but car and truck batteries often sold on 'cranking power', which is some hundreds of amps. A/H rating doesn't give a true picture of what the battery can (or needs) to deliver when starting an engine, especially in sub-zero temperatures.