BST38 & BST40 Slide Guide Installation

Slip the slide guide o-ring over the boss on the underside of the slide guide and make sure it is more or less seated in the o-ring groove. In order to prevent the o-ring from becoming dislocated, all operations from here until the main jet has been finally tightened must be performed with the slide guide upside down. Slip the emulsion tube through the slide guide. It is normal for the fit to not be as tight as it was between the used components (this will tighten after the main jet is screwed in and the components have been through enough heat cycles). Orient the emulsion tube’s keyway so that it will align with the locating pin in the carburetor body’s corresponding bore. Slip the slide guide/emulsion tube assembly into the carburetor body until stopped by the tabs at the top of the slide guide. In order to keep the emulsion tube in position, temporarily screw the main jet into the emulsion tube without the main jet spacer. If the tabs align well enough, you may be able to just push the guide home until the tabs seat. There is however a good chance that you will find that the upstream facing tabs are pinched inward a bit, in which case the slide guide can be flexed apart some while pushing on it (the use of tools to do this is not only unnecessary, but will damage the guide). After the tabs are started, push the guide home as far as you can – it’s OK if you can’t get it all the way in yet (Do not file the tabs in an effort to ease assembly! Doing so will ruin the slide guide and cause the slide to bind). Remove the main jet, slip the main jet spacer over the end of the emulsion tube and reinstall the main jet. Tighten the main jet to 16 in-lb (1.8 Nm), which will fully seat the slide guide.