1235 tach going weird

razerface

Member
I have a 4x4 1235 . When it is cold out, and you rev it over 10,000 rpm,,it makes a crazy noise, then the needle goes to the max. To get it to read correctly again, you have to shut tractor off and restart, if you let it idle long enough, it seems to work ok, so I assume the engine heat finally fixes it. Any ideas?
 

bakerg

Member
My MF GC2400 has done the same thing. Must be a design problem with MF. Have been told it only does it when it's cold but no one seem to know if it's the cable or if it is the tach itself. When it happened to me I just loosened the cable nut and the noise stopped.
 

California

Super Moderator
Staff member
Site Supporter
The tachs and speedos I've opened up have a magnet (from the cable) spinning inside a metal cup. The needle you see is attached to the cup.

A little bit of rust will make the cup drag and spin up to max. (really 10,000 rpm???) :mrgreen:

I repaired one by squirting a little lock fluid - graphite in solvent - in where the cable goes into the case. But if there's rust in there, the real repair is to replace the tach.
 

razerface

Member
LOL,, no, not really 10,000 rpm. I need better proof reading.
You squirted into the tach, or the cable?

I'll also try bakerg's solution and loosen the cable,, or tighten it if it is already loose.
 

California

Super Moderator
Staff member
Site Supporter
A dry cable can flop around at uneven rpm, and lubing it should stop this. But a screech is more likely to be in the tach head.

I bought another 30 year old Yanmar a couple of years ago. The tach was as you describe, screechy and jumpy before it warmed up.

I took the tach out, set it face down, and dripped a little graphite lock fluid into the bearing where the cable enters the case. (the only access point to inside - its otherwise a sealed unit). Then let it sit for a week. This fixed it.

I used this technique years ago on a BSA motorcycle, and on a couple of old cars - where it worked some of the time.

But as I noted, replacement of the sealed unit is the only way to expect years of service.
 
Top