Haven't been able to find much info on this, so I just did it myself and did some testing along with it.
I own a 2017 Honda Rebel 300 (pic below)
Tachometer: Hardline 2 cylinder (grey box pic below)
First: You will need to find your spark plug. I've posted before and after pictures below. There will be a rubber boot on the spark plug and a rubber tube covering most but not all of the wire. In-between the two rubber pieces is where you need to wrap the wire that comes with the tach. Wrap it around that area a minimum of 3 times, tightly, then zip tie the remaining wire to itself to hold it there.
Second: You will need to run the wire to wherever you have decided to place your tachometer. I ran mine along other wires, it took a couple tries to figure out exactly how I wanted it. Make sure the surface you run the wire along is not hotter than 125 degrees at any given moment, dont mess that up
Third: You are going to run the wire through the first opening in the tachometer (2 sided hole) and into the remaining hole which has a rubber backing. Tighten it up after you place it into hole #2 and you are good to go. Tachometer installed!
Note: the wire that came with the hardline tachometer was very short. It's an 18 gauge wire with steel instead of copper. This bothered me so I purchased some 18 gauge copper wire (5 bucks at auto zone) and used that instead. After testing both wires I found the copper wire to read more accurately by 500rpm.
Also Note: Im a newbie motorcyclist making this post for other newbies, If your an expert I insist you chime in and correct me if im wrong about anything or if you have any additional information to add!!! . Thanks in advance.
The bike idles at 1500 RPM which I think is normal, considering the CBR 300 idles at 1600.
From the readings on this tach I find shifting much easier.
Lower than 3k RPM > downshift
Higher than 5500+ RPM > upshift
Cruise anywhere from 2.5k to 5k (situational I try and stay around 4k cruising)
Again this is for a rebel 300, 500 guys yours is prolly different bc of extra cyl.
1st to 2nd 12 to 23 MPH RPM 5k - 7k
2nd to 3rd 20 to 32 MPH " "
3rd to 4th 35 to 40 MPH
4th to 5th 45+ MPH
5th to 6th 50+ when your on a freeway or straight road w no traffic,
I havent ran the RPM higher than 7k because the engine is screaming to be shifted at that point, maybe I'll do it for the sake of science later and post redline here, but I have not found the redline yet. The tach says its 10,100 and im not sure that is very reliable bc I havent tested it yet, dont want to hurt my babygirl.
Ever since I found this forum i wanted a very specific time to shift, I searched for hours on the forum to find the right info. What I've learned from having a tach as a reference is that it is situational, and you have about 10mph of grace between gears. Sometimes I shift at 5k, sometimes 7k, sometimes 3k depending on the situation, downshift for hills for extra power, etc etc etc. One thing I did learn the hard way is you need to downshift at the lower speed for the gear your going into. For example Ill only go from 2nd to 1st around 10mph to avoid a nice jolt, I dont like engine breaking =/ maybe I will in the future but for right now I play it safe until I have more experience. Everyone has been telling me to "listen" to my bike, i'd love to be able to do that but I have a shotgun exhaust so its kind of difficult to hear anything other than that. If i ever got my hands on the stock exhaust i'd have no need for the tach. Yes I can listen to the exhaust and base my shifting off that and I am, but for the sake of OCD I created this post. Hope it helps. Again, any input is appreciated!!!! Let's learn together guys these are beginner bikes for the most part.