dabomb Posted March 8, 2007 Report Share Posted March 8, 2007 Does any one know how many turns the mixture screw has to be out?? Cheers Quote Link to comment Share on other sites More sharing options...
sr34 Posted March 9, 2007 Report Share Posted March 9, 2007 from the 2002 manual Slow Jet And Air Screw The air screw meters air that is mixed with fuel metered by the slow jet. . Turning the air screw clockwis e, enriches the mixture: counterclockwise leans the mixture. Turn the air screw in until it lightly seats, then back it out to specified position. Air screw opening: 1 turn out After warming up the engine, connect the tachometer and slowly turn the air screw in or out until the engine revs up smoothly . Adjust the idle speed by turning the throttle stop screw. Install the jet needle into the throttl e valve. Install the thrott le valve spring and cable setting plate onto the carburetor top cover, then connect the throttle cable to the throttle valve whil e compressing the throttle va lve spring. Installation Install the carburetor in the reverse order of removal. Install the throttle valve while aligning ~ groove ~h the guide in the carbureto r body. Idle speed: 1.300 '" 100 min" (rpm) Quote Link to comment Share on other sites More sharing options...
fastducs Posted March 19, 2007 Report Share Posted March 19, 2007 FYI montesa changed carbs in 2001 from Dellorto PHBH series to PHBL series. But as far as air screw goes, it is tunable for each specific bike to match conditions of the day, such as altitude, temperature, humidity, pressure. I'd start with 1.5 turns out from fully seated, and go from there, assuming that your jetting is pretty close to begin with. Keep in mind that the air screw has the most effect from closed throttle to about 1/8 open. The rest has to be done with jets and needle. Quote Link to comment Share on other sites More sharing options...
samandkimberly Posted May 20, 2010 Report Share Posted May 20, 2010 I've been trying to adjust the mixture screw on my 2000 315 and finding it has very little impact at all. Fortunately the bike ticks over pretty well regardless of the setting, but I'm curious if anyone else has experienced this? My gut feeling is that the passageway must be plugged up, but is this were so I wouldn't think it would want to idle. Sam Quote Link to comment Share on other sites More sharing options...
wherry Posted May 21, 2010 Report Share Posted May 21, 2010 PHBH. Mixture screw adjusts air. Around 1.5 turns out. PHBL. Mixture screw adjusts fuel. Around 3.5 turns out. It'll say on the side of the carb which one it is but if that's difficult to see the PHBH has the mixture screw towards the back (air-box side), PHBL has screw engine side. Quote Link to comment Share on other sites More sharing options...
samandkimberly Posted May 22, 2010 Report Share Posted May 22, 2010 Thanks, everyone. I have the earlier PHBH carb, and understand relatively well how it works; I'm just surprised at how little effect it has on idle/off idle operation. From about 1/4 turn open on to 2-3 turns open it acts very similar, the exception being that it needs to be warmed up a little for the idle to be good at 2.5 + turns. I finally settled around 2 turns out. It's really not a problem, in that the the bike runs well over a wide range. I'm going to remind myself that the enemy of "good" is "better" and leave it alone. Sam Quote Link to comment Share on other sites More sharing options...
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