sticking rev counter

[tim wood]

Hi Guys,
I am asking for bit of guidance here. The rev counter on my 4.2 sometimes/ occasionally sticks at around 2500 rpm. On other occassions its perfect. Would this be the generator or the instrument. What do you think? If it is the head would one of Dave Rawles boards help or is it a specialist to overhaul ?

all help much appreciated

Tim

[Heuer]

It could be the generator magnets are getting weak. Dave's board uses frequency rather than amplitude to drive the tach so worthwhile doing and relatively simple: http://etypeuk.com/forum/viewtopic.php?t=292

I had this problem and fitted Dave's tach board to no avail. With Dave's board you can use the PC based frequency generator to swing the needle backwards and forwards - this can show up the sticking point. Unfortunately because you can adjust the amplitude of the PC generator output it is easy to think the problem has gone away. I solved it by washing the bearings with switch cleaner and then gently swinging the needle back and forth through its complete arc by hand many times. Do NOT use oil! I know Ray Livingston created a programme to swing the tach needle constantly for hours on end which cured the problem but that software only works on his 'homebrew' modded system.

Alternative is to send the tach to Speedograph Richfield for service

[daverawle]

Tim,

I'm not sure how it happens but some meters have a small amount of end-float (perceptible by pulling on the pointer) and they seldom stick. Others have no end-float and are sticky. But as David said; the best course of action is to clean the bearings throughly using carbon tet or switch cleaner and then lightly lube. If you decide to use one of my boards I have a set of frequencies to exercise the movement which may help after cleaning.

Dave