mightypeesh Posted May 20, 2016 Share Posted May 20, 2016 Hi folks. Continuing my learning curve in the world of internal combustion power I have bought an OS 48 Surpass. It is my first four stroke and am a bit stumped by the lack of pressure nipple on the muffler. It has a black screw in its place blanking the hole which looks like it has always been there. There are no other vents anywhere on the engine. Is this correct or should it have a nipple? If it is correct, do I just leave an open vent to the fuel tank to allow air to replace the fuel used? If it should have a nipple does anybody know the size of thread required to fit it? Cheers, Simon Edited By mightypeesh on 20/05/2016 11:40:20 Quote Link to comment Share on other sites More sharing options...
John Privett Posted May 20, 2016 Share Posted May 20, 2016 My old OS FS40 Surpass has a pressure nipple in the location yours has the black screw. I don't know what the thread is - you can remove your black screw and measure it I guess! I'd be inclined to just run it without pressure - leave the tank vent open. Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted May 20, 2016 Share Posted May 20, 2016 Fit the nipple mighty, this may have been left off to rectify a tuning issue. Fit pressure and retune. Also check the tappets are not too wide, about 4 thou. Check the main needle for slop and fit some fuel tube to seal this, if it is leaking Quote Link to comment Share on other sites More sharing options...
jrman Posted May 20, 2016 Share Posted May 20, 2016 Try it without pressure. I have never used pressure on any of my OS 4st from the smallest 20 up to a 90. Quote Link to comment Share on other sites More sharing options...
Former Member Posted May 20, 2016 Share Posted May 20, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
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