Yes, you have very correct understanding.
>I see desired sequence like this.
>1. turn on engine run switch
>2. fuel pump PWM's to some pressure and consumes ?? mJ.
Yes, most spread motorcycle fuel pump use 43psi or 3bar pressure. This pressure is comfortable, but in future possible decrease it to smaller value up to 15psi or 1 bar. Distances and hoses length in small engines very short. For 43psi this pump have performance 35lph, my biggest 30hp engine in a full consume 12 hp per hour max, in realty up to 5 liter per hour in normal flight, so energy wasted by the pump.
Seems new pump with 50 lph models like
https://aliexpress.ru/item/32913333564. ... web201603_
declared 1,7 A for 12V or 20W (dont tested personally)
This eat less than 35 lph pumps I tested before. 2A for 12V or 24W
https://aliexpress.ru/item/32899157341. ... web201603_
This 20..24 W is too much for scooter generator which generate max 50W in a full rpm.
If PWM decrease pump consumption to 12w or less it will already acceptable, the less the better.
Instead of mechanical pressure should used Fuel Pressure Sensor like
https://aliexpress.ru/item/32998009174. ... web201603_
or https://aliexpress.ru/item/33035893349. ... web201603_
Megasquirt 3 supports this type of regulation and in Tuner studio it can be regulated
or any of
https://aliexpress.ru/item/400026315970 ... web201603_
A lot of variants to choose
>3. ECU blinks some kind of light or beeps or does something to let you know it's booted, fuel pressure is ready, priming pulse has been delivered >etc. Injector consume ?? mJ, and fuel pump also turns back on and consumes ?? mJ.
Yes, blink and sound together which means engine ready to start.
>4. you pull start cable
Yes. About 20% of enfines will have electrical starter, but it should work the same like pull starter.
>5. when single cam pulse comes along, you send a 5V or 12V level signal to the coil. Coil has igniter which bumps this voltage up to around 400V for >the primary side of the coil. As well the injectors causes the pump PWM to kick back in.
Yes. 12...18V battery will be on board
The best suited for 125...250cc throttle bodies are https://item.taobao.com/item.htm?spm=a2 ... =19#detail
I have 5 in hands. I can CNC mill throttle bodies. The most popular is 24...32mm
PS. One offtopic idea is to use just dosing pump without any injector nozzles. Just meter correct quantity of fuel to carburetor body.