PARTS AND ADVICE FOR YOUR 'OLDEN GOLDIE'
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Carburettor Needles and Slides
The carburettor needles are held into the slides by a threaded alloy plug, accessed down the hole in the slide guide pin. A straight screwdriver slot enables it to be removed for cleaning and changing the needle.
The needles need to be able to swing a little in the slide, although not to move up and down, in order to allow them to line up with the jets.
On a carburettor set I have just been rebuilding I noticed that the needles were held rigid in each slide. This was obviously not correct. On removing the needle and examining inside the guide bore, I determined that the plug had been screwed down with enough force to destroy the very narrow ledge that serves as a plug stop.
Thus the plug could now reach the top of the needle and hold it firm.
The only solution to this, short of replacing all four slides, was to use Loctite on the plug threads, screwing the plug in until it contacted the needle and then backing it off about a quarter of a turn, so that the needle had some lateral free play.
So, if you have occasion to remove that plug, please be careful and only tighten with a 'nip', not put your whole weight behind it!
There are effectively two slide types.
GL1000 775A and 775B carburettor types had slides with a 'scalloped' bottom edge. When fully lifted this arced bottom edge matched the bore and thus allowed the fullest mixture flow through the carb.
Later GL1000 , GL1100 and GL1200 models all had slides with a 'flat' bottom which undoutedly interupted the air flow to a very small, probably immeasurable, amount.
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The GL1100 carbs had a problem of the slides sticking and becoming scored, sometimes very badly.
Honda even tried Teflon coating on some carb versions. If you have these, you will see that the slides are black. But eventually, Honda simply chamfered the sharp edge where the slide bore meets the main bore to stop it digging into the slide.
Please note: All these carbs are very susceptable to dirty air. Keep your air cleaner fiter changed regularly.