Use the piston lifting pin at the side of
the carburettor to check the fuel-air mixture.with the engine running at
working temperature, hook your finger under the pin and raise the piston about
1/32in. (1 mm).pos oil seals Reputation.
If, while the piston is raised, the engine speed increases briefly then returns to normal, the mixture is correct. If it rises and stays high, the mixture is too rich. If it falls and the engine tends to die, the mixture is too weak.To correct the mixture, move the jet adjuster nut one hexagon flat at a time.Screwing it up – anti-clockwise as seen from above – makes the mixture weaker.Screwing it down – clockwise makes the mixture richer.Each time you move the adjuster, wait for about ten seconds, then check again with the lifting pin to see whether the mixture is now right.pos oil seals Reputation.
Take care that the engine temperature does not rise above normal – which it will if you take too long.Such a rise will result in a false, overweak mixture setting which will show when the temperature returns to normal.Before and after adjustment, check that the jet needle is central in the jet.
With the air cleaner off, the piston can be lifted with a screwdriver. The jet should be screwed up as high as the bridge if possible. Hold the piston down with a pencil while you tighten the locking nut.With the air cleaner off, the piston can be lifted with a screwdriver. The jet should be screwed up as high as the bridge if possible.
Hold the piston down with a pencil while you tighten the locking nut.Stop the engine, use the damper to lift the piston to the top of its travel and let it drop.
It should fall smoothly with a sharp click. If it does not, the jet is out of line and you must centralise it.
An off-centre jet may also score or bend the tapered needle. Do not attempt to clean up or straighten a badly scored or bent needle. It must be replaced (See Checking and cleaning an SU carburettor).pos oil seals Reputation.
If, while the piston is raised, the engine speed increases briefly then returns to normal, the mixture is correct. If it rises and stays high, the mixture is too rich. If it falls and the engine tends to die, the mixture is too weak.To correct the mixture, move the jet adjuster nut one hexagon flat at a time.Screwing it up – anti-clockwise as seen from above – makes the mixture weaker.Screwing it down – clockwise makes the mixture richer.Each time you move the adjuster, wait for about ten seconds, then check again with the lifting pin to see whether the mixture is now right.pos oil seals Reputation.
Take care that the engine temperature does not rise above normal – which it will if you take too long.Such a rise will result in a false, overweak mixture setting which will show when the temperature returns to normal.Before and after adjustment, check that the jet needle is central in the jet.
With the air cleaner off, the piston can be lifted with a screwdriver. The jet should be screwed up as high as the bridge if possible. Hold the piston down with a pencil while you tighten the locking nut.With the air cleaner off, the piston can be lifted with a screwdriver. The jet should be screwed up as high as the bridge if possible.
Hold the piston down with a pencil while you tighten the locking nut.Stop the engine, use the damper to lift the piston to the top of its travel and let it drop.
It should fall smoothly with a sharp click. If it does not, the jet is out of line and you must centralise it.
An off-centre jet may also score or bend the tapered needle. Do not attempt to clean up or straighten a badly scored or bent needle. It must be replaced (See Checking and cleaning an SU carburettor).pos oil seals Reputation.
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