Sidestand Cutout Safety Switch Circuit

G'day fellow crayzee KZ riders - as promised/threatened a while back ,I was gunna design and post a safety circuit to enable you to start the bike while it's on the sidestand - for warmup purposes (as long as the bike is in neutral). This is for older bikes which may have had the luxury of a clutch cutout but no safety circuit to prevent you riding off with the sidestand down. (Who's ever done that.... :lol: ) Anyway, I finally got a round tooit and here is a draft version of the design for your enjoyment. My apologies for nil detail on how to put it together or of components but I haven't built it yet. ( I've been busy finishing off the rolling chassis of my Z1-R resto.) If anyone gets to build it let us know how it goes and post some pics of the implemented design for our guys. I hope to post some updated pics soon of my rolling chassis after I complete the fron brake rebuild.

A quick description of how the circuit works - IC1 is an "AND" gate and its function is to control transistor Q1. When both of its inputs ( 1 from the sidestand switch AND 1 from the Neutral lamp) are"High" Q1 is "ON" allowing current to pass through the coil of Relay RL1 which closes relay contact RL1/1. This places an earth on the Ignition Kill Line and disables the start circuit. This engine kill function is only enabled when the sidestand is down AND the engine is in gear (ie NOT neutral). As long as neutral is selected, the engine can be started with sidestand down. If the sidestand is in the fully up position the engine may be started whether in gear or not - but of course the normal clutch lockout (if fitted) will only enable the engine to be started with the clutch lever pulled in. Some earlier bikes may not have had a clutch lockout switch but then they mostly diid not have a kill switch circuit either.
Hope I have explained this ok for you ...?

I noticed you don't seem to have an active state on the side stand switch when it's open, a pull down resistor will help define that state. The neutral input gets a pull up from the neutral light itself based on your diagram.
Also, it's good practice to put a flyback diode across the relay coil to absorb any spikes when it is de-energizedenergized.
Lastly, with the abundance of logic level only electronics out there I'd be tempted to add a disclaimer that only components that can survive over 12V (maybe 25V rated?). should be used.

The last bike i owned with a side stand switch killed the bike if you let the clutch out with the side stand down, is this circuit a more common approach? I'll admit my experience is with electronics, not bikes

In addition to what zero10 said, it appears you are shorting the output of the AND gate through the base of Q1. You will want a current limiting resistor there to prevent burning Q1 or IC1.
There is an issue with power for IC1. Cmos probably won't handle the 12v power without some conditioning. Even TTL could have troubles. You could just do away with IC1 and use BJT's. They can handle all the dirty power from the bike's charging system without any strange behavior.
Also, what are you shorting out to kill the ignition? KZ's normally open a circuit to kill the ignition. If you short the primary circuit, you run the risk of overheating the coils.

Here's a simple circuit. But it only works as long as the kickstand switch and neutral switch are very reliable:

D1 is needed for the flyback on the relay coil to protect the neutral and kickstand switches.
D2 is needed to isolate the neutral light from the kickstand switch. If there is no neutral light, D2 is not needed.
D3 is needed for the flyback on the ignition coils to protect the relay contacts.

Factory kickstand safety circuits get flakey due to the switches. Then the ignition becomes intermittent.

I have a BJT version if you're interested. In that version, it defaults to keeping the motor running if the kickstand switch fails.

Thanks zero10 and loudhvx for your constructive comments and suggestions (all valid) which address the design flaws in my (over) simplified design!
Zero10's design looks to be a simple solution with minimum components required.
The transistor version with the feature which addresses the sidestand switch failure mode sounds good - would like to see this one too .

There are two versions. The simpler version is really just to show functionality. The extra components are for arc suppression and to guard against transistor leakage.




I have not built any of these circuits.

Here is the simplified version of the first one. It illustrates the functionality, but is missing some of the safety components which promote longevity.