Kill Switch Theory

[Smoker]

Rode dirt bikes most of my life.

Every dirt bike I've owned came from the factory with a push-button momentary kill switch.

Every street bike I've owned came from the factory with a toggle on-off kill switch.

I'm guessing that dirt bikes have a momentary switch so I don't kill the engine by accident. Are there other reasons for using a momentary switch vs. an on-off toggle switch?

I tried searching, but didn't find much on the topic.

[Darrell]

Do four stroke dirt bikes have a toggle or momentary kill switch? I'm just guessing, but maybe it has to do with the ancillary electronics on a street bike. My dirt bikes (all two strokes) have no battery and I think the kill switch just removes ground from the CDI unit so the spark dies. On my street bikes, nothing works when the run-off switch is open. On a dirt bike, that switch is a KILL switch, but on street bikes it's usually labeled "Run OFF", right?

[brrrappp]

Street bikes require a positive shut off switch on the handlebar so that you don't need to take you hands off the bars to kill it. Dirt bikes don't have any such requirements.

In the old days on open-class MX bikes some riders used the kill switch like a jake-brake under certain conditions. In my opinion, for dirt bikes, you don't want the guy next to you on the start line switching your bike off 5 seconds before the gate drops. You don't want a toggle type switch because you loose races and or crash when your engine stops unexpectedly in the middle of the whoop section. Imagine your body slammed into the bars as your bike started swapping, you might want to gas it to straighten out but your engine just stopped and your on the ground. Or imagine you just pulled a tear-off and missed the handle grip while landing a jump. Or you slide out in a turn and in your haste to pick up the bike, you hit the toggle to off.....then you kick and kick and kick until you're in last place before you see the kill toggle is in the off position.

[JonW]

Switching the roadbike RUN/STOP switch off at the lights when racing your friends was one of those things we did back in the day :)

'Mates' even did it when you parked up, made you look like an idiot in front of girls... lol

[85RZwade]

Yes Darrell, four-strokes dirty bikes have the momentary switch as well. Answering for a friend...

[waltmil]

Explanation from years ago, the dirt bikes have a momentary button on the left side because if you crash throttle side down and the throttle is wide open, the kill button is up and easy to find. Why street bikes have a switch on the right is probably due to some supposedly helpful regulation.

[brrrappp]

Here is some links with "light reading" for those that want the detailed US Federal requirements in the USA for STREET motorcycles.
Off Road motorcycles are mostly excluded from these rules but have some CPSC (consumer product safety commission) standards. "Common sense" and customer demand rules the placement and use of various controls on dirt bikes. ATV's often have an on/off vs MX bikes have a temporary kill. Some ATV's, Snowmobiles and watercraft have a deadman kill switch.

It should also be noted that in the USA a State can make it's own requirements for inspection, emissions, and safety. California Air Resources Board emissions is one example.
Back around 1992 New Hampshire decided to require a brake light for ATV's. Several other States adopted that standard and eventually it became an industry standard. OEM's used to ship a dealer installed kit with each ATV destined for NH that included a brake switch equipped master cylinder, tail light, and other misc parts in order to comply.

https://www.law.cornell.edu/cfr/text/49 ... footrests.


https://www.govinfo.gov/content/pkg/CFR ... 71-123.xml

[Smoker]

Thanks, guys. Definitely appreciate the input.

Makes sense that there could be a regulation for kill switches on street bikes.

Functionally, I don't see much difference. Both, the momentary and the toggle have just 2 wires, so seems like either one would work.

I know that on my WR, besides shutting down the spark, the kill switch cuts off the fuel pump, fuel injector, intake solenoid, fan motor relay, etc. So, it affects a lot more than just the coil, but still could be a momentary switch vs. a toggle.

Of course, I'm asking because I want to swap the toggle kill switch on my RZ for a momentary kill switch. Looks like it should be no problem.

[85RZwade]

Don't tell the Feds, but my on/off switch went away decades ago when I switched (pun intended) to a different throttle. I always use the key anyway.

(Not a recommendation or legal advice!)

[Darrell]

"(Not a recommendation or legal advice!)"--- OK, THAT made me laugh.