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Carburettor - Dashpot maintenance

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Carburettor - Dashpot maintenance

Postby TechTeamMod » Tue 9th Sep 2008, 09:01pm

Here's what you should be doing to your Carburettor sometime soon.

Remove the screw at the top of the dash pot and remove the plunger. Now get a small torch and have a look inside. You will see some threads. Below these threads you will see a shoulder. This is the actual piston that you needed to put the oil in. You need to fill this smaller diameter inner hole to within around 5mm of its shoulder (and not up to the threads).

There is no 'ideal' oil as carbs will have different machining tolerances. Below is a list that may be used as a starting point:

  • For 1275 Standard Engines, you need to use 30 weight oil (10w30)
  • For 998 Standard Engines, you need to use 40 weight oil (10w40)
  • Tuned Engines of 1275 and above will need 20 weight (5w20) (or ATF Fluid or Redex)
  • Tuned engines of 998 to 1100 will need to use 30 weight oil (10w30). A useful alternative for this is 10w40 mixed 50/50 with 3 in 1 oil.
Its all to do with how fast you want your needle to rise.

Performance engines can cope with the extra fuel as they also usually have an improved air intake, so a lighter oil is better, but on an economical running car, you don't need lightning acceleration so a heavier oil, giving a nice steady lift of the needle, is what is required.

Dashpot oil should be on your checks list at least once a week, when you check your engine oil.

Incidentally, a slight overfill occasionally is actually a good thing. It will ensure that the moving surfaces of the outside of the piston is kept lubricated.

At worst, a very small amount of oil will go into the carb and then engine and get burnt. If you use Redex as your dashpot oil then it will actually do your engine more good than bad.

Every 6 months, you should remove your dashpot completely and de-gunk everything. This will make sure you don't suffer from the "Sticking Dashpot" scenario, and having an engine that just will not accelerate.

A nice little 1 hour Winter Indoor Maintenance job for all SU carb Mini owners.

Happy Miniing, Steve Ed
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