I stripped my carb today (26VA) to attend to a worn butterfly spindle. I was slightly surprised to find countersunk screws holding the butterfly on, not particularly tight. Should there be any means of securing them? (loctite perhaps?).
Second question, what is the function of the three holes outlined on the emulsion block? The bottom one was blocked by a swollen gasket and I'm wondering if this explains my running problems.
25-06-2023, 02:44 PM (This post was last modified: 25-06-2023, 02:46 PM by John Cornforth.)
Hi
From what I can work out from my Zenith data, and looking at the gasket holes, the three holes you have ringed all take combined fuel (with some metered air) from the Compensating Jet, Capacity Tube and Slow Running Jet through to the discharge 'beak' on the other side. The very lowest passageway (with fixing screw passing through) is associated with the main jet.
I have seen advice to lap the block face to the mating casting before assembly with a new gasket. Beware that the fixing screws are not all the same, and the lowest needs a fibre sealing washer under its head. The gasket is made vertically symmetric so it doesn't matter which way round it is fitted.
In my experience, carburettor castings may suffer from flaky corrosion in the small passageways which is hard to remove. A good blast with an air line is recommended.
There should be some mechanism to lock the throttle disc fixing screws, e.g. by peening them over or having split screws which are slightly splayed after tightening. I guess these days Loctite would be appropriate
That's very helpful John, thank you. I lapped the emulsion block onto the bowl a couple of years ago when it began leaking. A very easy fix I thought but the replacement gasket seems not to have been petrol proof and had swollen up into all the void areas. Now assembled with a new gasket of a different make.
I suspect if this is main-jet connected then that was not the cause of my problems. No matter, it needed to be fixed!
