November 19, 2015
Bros PGM vs Non PGM Tach Compatibility
Bros PGM vs Non PGM Tach Compatibility
The tachometer seems to be reading double what it should; at normal idle it reads 2krpm and by the time I have the engine half wound up the needle is past the red.
Eliminating the possibility of having Idle set too high and driving like a madman, I think perhaps my PGM bros doesnt want to play ball with the seemingly non PGM clocks.
Anyone ever hear of this and have any workarounds? On doing some digging I have unearthed the below from another forum which seems linked:
” now have the older engine in the newer PGM version frame- the only difference in terms of wiring that goes to the engine is the Throttle position sensor and the Pulse generator.
Throttle position sensor is not important, you can just swap the carbs over and connect it or leave it disconnected. Runs fine without being conected, go figure…
The pulse generator is easy to get to and swap over. Just remove the clutch side cover and it is right there on the top right hand side near where the cable enters.
The older engine has two pulse generator sensors, leading to a four pin connector that joins the loom on the frame near the front cylinder head.
The newer engine has one sensor that leads to a two pin connector in the same place.
The toothed wheel that generates the timing pulses is different, the double sensor version has half the number of teeth. Makes sense….
The wheel is held on with a very tight bolt with a rubber washer underneath. You will need to counterhold the crankshaft at the other end to undo it, with a breaker bar. Have fun. I did. The wheel goes onto the shaft with splines that are designed in such a way that it can only go on one way, so don’t worry about putting the engine at TDC.
So having swapped the sensor and wheel the older lump should work with the newer PGM loom. This should work the other way too as the new lump still has the bolt holes to mount the pair of sensors.
I haven’t run the engine up yet as I ran out of daylight yesterday and won’t be able to finish it off till next sunday. If it blows up I’ll let you guys know.”
I know just enough to be dangerous, but I dont really want to go messing around with pulse generator sensors on a PGM bros to have it work with old clocks :wassat:
Any advice appreciated :thumbsup2: