Tick, tick, tick, tick........... crap!

[TomLS]

Just rebuilt my old s.u pump and refitted it for a test run, all sounded well and then it just stopped! After much fart-arsing around (in the pouring rain!) I discovered that the diaphragm had become jammed in, causing the contacts to be permanently made (the thatp was RATHER warm after that). I from memory of the build, I think the reason for this is the 'armature guide plate' (from the instructions) or the '5 little plastic figure 8's' (which is what my pump has).
How tight fitting should these be? Mine seemed rather tight when I built it so I just re-used the old ones which were fine, and a little looser, however I still thought a bit tight!

Can I just shave some plastic off the edges of them to make them a looser fit?

Cheers,
Tom.

[les]

Did you stretch the diaphram before tightening the 6 outer screws? Also there is an adjustment for the contact breaker 'throw-over'. Set properly the pump components will not need altering.

[bmcecosse]

Exactly - diaphragm must be stretched and points set correctly. Don't 'shave' anything.

[TomLS]

How do I 'stretch' the diaphragm? I followed the instructions supplied with the rebuild kit and set the diaphragm tension. Pushed in fully, rotated until the contacts just 'throw over' then rotate a further 4 holes. I also measured/adjusted out the arms of the points to 2.3mm on the bottom and 0.9mm contact displacement at the top, exactly as instructed.
The only discernible difference between the old build and the current one (apart from the disintegrated points) is the tightness of the armatures.

[bmcecosse]

Try again - bit looser this time - so it throws over nicely.

[les]

The minor workshop manual has a comprehensive proceedure for setting the pump. Rather too involved to type out here. the diaphram is 'stretched' by pulling it into the maximun shape it goes when in use.

[TomLS]

Oakey doakey, guess I'll just have to try again!
I have the Minor Workshop manual, the Haynes book of lies, and the instructions that came with the pump, and I did it all by the book, honest gov'!
Will try again tomorrow...

Cheers folks