David the flyer Posted October 12, 2010 Share Posted October 12, 2010 Hi, i have a Laser 70/75 (not sure) 4 stroke, and when i start it up the engine raws away to high and if i try to throttle up the engine cuts out, i have to leave the glow plug statrter on, restart the engine and that some times works, by bringing the revs down to what they should be on tick over and when i throttle up it runs normal? and clues to why this happens? as it does take a few restarts to get it running nice? thanks Dave Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 12, 2010 Share Posted October 12, 2010 Air leak on the inlet manifold or carb? Can't think what else it could be. Quote Link to comment Share on other sites More sharing options...
A.A. Barry Posted October 12, 2010 Share Posted October 12, 2010 Me thinks, that there is a bit of crap in the needle valve??? A.A Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 12, 2010 Share Posted October 12, 2010 Air bubbles in the piping? Could be a routing issue allowing a partial airlock to develop leading to a lean mixture until it's cleared after drawing some fuel through. Quote Link to comment Share on other sites More sharing options...
David the flyer Posted October 12, 2010 Author Share Posted October 12, 2010 Hi thanks for that whats the best way to get rid of that? Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted October 12, 2010 Share Posted October 12, 2010 Can you get at the carb to prime it? Sometimes 4-strokes take a little while to establish a solid fuel flow to the engine. By priming you help them along the road as it were! I have one which is a pig to start first time - I really have to whizz it over on the electric starter for a good 10secs without the glow stick on just to "get the juices flowing". Then apply the glow starter and it usually starts next burst from the starter. Once it has done a run - if I want to start it again a few mins later - even though its gone cool it will start by just flicking the spinner backwards against the compression - that easy. But if I leave it say an hour - by which time the fuel will have flowed back along the fuel line into the tank - then try to restart it its back to square one! BEBEdited By Biggles' Elder Brother on 12/10/2010 14:34:19 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted October 12, 2010 Share Posted October 12, 2010 Sounds odd, BEB, in my experience 4 strokes draw fuel up much better than 2 strokes.....!! Dave, which way up is the motor? If inverted could the plug be being bathed in fuel & taking a while to "burn it off"?? Quote Link to comment Share on other sites More sharing options...
David the flyer Posted October 12, 2010 Author Share Posted October 12, 2010 yes the engine is inverted, to be honest thats what i thought, so do you think leaving the glow plug starter on would help? Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted October 12, 2010 Share Posted October 12, 2010 Yes definitely....4 strokes have more metal mass than 2 strokes & only fire half as often so they take a while to warm up.....fire it up & run at a fast idle for 30 secs to a minute before removing the glow starter.....then let it warm up for another minute at about 1/4 -1/3 throttle..... Then see how it throttles.... Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted October 12, 2010 Share Posted October 12, 2010 Posted by Steve Hargreaves on 12/10/2010 16:43:13: Sounds odd, BEB, in my experience 4 strokes draw fuel up much better than 2 strokes.....!! Yeah, but you know how it is - I've decided engines are like women - they all look the supericially the same on the outside but get down to details and they're all different! This engine likes that treatment - and if I follow that strarting procedure, no problem. But if I depart from the script I can easily spend the next 10 mins trying to get her to fire up for the first time, or after an extended break. BEB Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted October 12, 2010 Share Posted October 12, 2010 BEB All to do with strokes then ! Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted October 13, 2010 Share Posted October 13, 2010 Ah yes.....few women will fire up after an extended break.... Quote Link to comment Share on other sites More sharing options...
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