tac problem

[Sharpie]

I installed a tac on my 4 cycle engine it came off a 2 cycle now it reading double anything i can do to fix that?

[Tomo]

hi
a 2 stroke tach counts every firing stroke which is once per revolution
a 4 stroke tach counts every second revolution or every firing
unless the tach is programable or has switches on rear it will not be able to be used
an automotive guage repairer may be able to change it to read 4 stroke properly [maybe cheaper to purchase correct unit]
tomo

[thebuggyman1]

Are you sure it is wrong? I may not be understanding correctly, but I think it should be right. A 2 stroke fires every revolution. A 4 stroke only NEEDS to fire every other, but due to the flywheel/magneto design I think it's firing on the exhaust stroke too.

[lewis]

Equus 8068 - Tachometer | O'Reilly Auto Parts

This tach will work on 1-12 cylinder 4-stroke engines. It is programmable and works good on our machines. Last one i purchased was around $80. Hope this helps.

Lewis

[plott hound]

Are you sure it is wrong? I may not be understanding correctly, but I think it should be right. A 2 stroke fires every revolution. A 4 stroke only NEEDS to fire every other, but due to the flywheel/magneto design I think it's firing on the exhaust stroke too.

you are corect.small engines fire every time piston comes up on TDC.

[Tomo]

hi
On small gas engines
some waste the spark and others are actually timed
Further different engine makers use different types of ignition systems
Different systems require different methods for wiring in tacho [some u r unable to ]
Then an appropiate tacho must be used also

For check and tune purposes use either contact tacho ,infared tacho ,inductive pickup tacho or a pulse pick up type [ diesel injector line ]

ps if u ever have used a automotive tacho/ timing light some will have a 2/4 stroke selector switch to half reading or double reading etc

tomo

[jerseybigfoot]

Most of the older oem 2 stroke tach's run off the alternator and charging coil. They see the AC before its rectified. There are outboard tachs that can read the same on 4 strokes and its a function of the number of poles and are adjustable.

[Sharpie]

thanks all for the info time to go shopping for a 4 cycle tach

[ArgoGirb67]

I bought a "Tiny Tach"for my OH 160 Argo.sensor wire wraps around spark plug wire.Also tracks Hours.Google it!