FricFrac Posted July 28, 2012 Share Posted July 28, 2012 I just rebuilt my triple Mikuni PHH 44s reinstalled and set the pilot screw to it's original setting of 1.25 turns out from bottom. The butter fly valves are completely closed and it will idle around 1000 RPM(ish) then it will idle right up to 2.5 to 3K RPM after a minute or so. That's with the starters turned off. If I play with the butter fly valve opening (idle set screw) and turn in the pilot screw to about 3/4 it seems to run but its rough. I haven't balanced it out yet. I'm trying to understand what's going on so a little direction on my misunderstandings would be great. My understanding is that the pilot screw adjusts the amount of air added to the mixture. Turn it in - less air. Turn it out - more air. So the part that confuses me is if I turn it in to 3/4 and open the butter fly valves it seems to run better. I can understand that the air is metered differently through the pilot screw adjustment than the butter fly valve but that would be at various RPMs. Shouldn't it be the same at idle? I rebuilt the carbs completely but I was told not to mess with the throttle plates and shafts so I never replaced the shaft seals. I'm assuming air could be leaking past the shaft but it never did before and I would think it would have to be a significant leak to go from 1000 RPM to 3000 RPM. Thanks guys any help is always appreciated! I'm dying to get this back on the road. The plan was to have it ready at the begining of the summer but I kept doing the "while I'm at it" lol. Quote Link to comment Share on other sites More sharing options...
Sam280Z Posted July 28, 2012 Share Posted July 28, 2012 If it is reving that high, air is getting in somehow. Make sure the throttle valves are closed enough. It should not run at all if the throttles are completely closed. The linkage can cause one or more carb to hang open a bit (since you haven't balanced them yet). Check for intake leaks - missing gasket, twisted o-ring, missing plug... Sam Quote Link to comment Share on other sites More sharing options...
FricFrac Posted July 28, 2012 Author Share Posted July 28, 2012 Why would it idle fine for a minute then climb to 3K. If there was a leak wouldn't it rise right away? Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 29, 2012 Share Posted July 29, 2012 Air Leaks, go check again. Quote Link to comment Share on other sites More sharing options...
Sam280Z Posted July 29, 2012 Share Posted July 29, 2012 It can't rev without air.Something is letting the air in. Quote Link to comment Share on other sites More sharing options...
FricFrac Posted July 29, 2012 Author Share Posted July 29, 2012 Would it have to be air before the jets? Or would it still draw air in after but go lean because it's not pulling fuel? Quote Link to comment Share on other sites More sharing options...
FricFrac Posted July 29, 2012 Author Share Posted July 29, 2012 Found the problem. The starters have a spring on them between the top plate and bottom plate and a circlip that keeps them from coming up off the shaft under the spring pressure. I made sure to align the tooth that seats onto the inner portion of the starter but the spring was pushing the top of the starter up too much and the tooth was disengaging. I'm getting a solid idle now - thanks guys! Now to tuning Quote Link to comment Share on other sites More sharing options...
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