View Full Version : Any one using TTO mini tachs?

herman pahls
08-04-2016, 04:42 AM
I noticed that Jody was using a Trail Tech TTO Tack on his 630 project so I ordered one.
When setting the tach for an engines particular ignition, you have a choice of .5, 1, 2 or 4 pulses per revolution (PPR).
I assumed that the Predator 420 has 1 pulse per revolution and trail tech confirmed that was the setting I should use.
At that setting the tach shows the engine idling at 800 RPM.
I question if that is correct because the Comet 40 series CVT has an engagement RPM of around 1600 rpm and at idle it is trying to engage.
When I drive it at full throttle with the governor removed it shows a top RPM of 4200 which seems reasonable.
Google says these engines idle around 1400-1600 RPM.
If I play with different PPR's I can get the tach to read 1600 rpm at idle and 8000 at full throttle, which I do not feel is realistic for a stock, no governor 420 Predator.
Any one have any answers?

08-04-2016, 04:49 AM
1 ppr makes sense as the ignitor coil gets a pulse each revolution of the flywheel.

Is the belt the correct width? Maybe the springs or weights have been changed? Any of these will change the engagement rpm.

800 rpm sounds pretty low for a single cylinder, is it barely running at that point?