1972 cb350 idle issues
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From: Timo Geusch on 15 Jun 2007 16:17 "mwhyte via MotorcycleKB.com" <u35079(a)uwe> writes: >> >>What's the idle speed set at? Also, the following potential problem >>areas come to mind: >> >>- Air leaks >>- Sticking float needle valve, although that would show itself pretty >> much all the time. > > When you say air leaks, where would be the most typical sites? In the carb, > or the engine (ie. head gaskets) themselves? Usually the rubbers between the carb and the inlet stubs on the engine. They'd be the only ones to have that kind of effect of leaning the mixture. > I'm considering getting a gasket set and just replacing all of them; I'm sure > they haven't been touched in 35 years ... Don't bother, it won't help in this case anyway...
From: mwhyte via MotorcycleKB.com on 17 Jun 2007 08:40 >Third, two of us have asked you nicely now what the idle speed is and you >have not responded. >SO WHAT IS THE IDLE SPEED......or don't you have a tach? > Sorry, missed that. When the choke is open (off), it's hard to tell, because it almost immediately stalls out and dies, so I can't tell. WIth the choke closed, even slightly, it hovers around 1000. >And lastly, given your (apparent) mechanical ability, you probably should >NOT be replacing the head (or other) gaskets on the engine unless you KNOW >they are a problem. Likely they are not. Good to know. I wouldn't attempt it myself in any case ... thanks for all the tips ... -- Message posted via MotorcycleKB.com http://www.motorcyclekb.com/Uwe/Forums.aspx/tech/200706/1
From: Ken Abrams on 17 Jun 2007 09:46 "mwhyte via MotorcycleKB.com" <u35079(a)uwe> wrote > Sorry, missed that. When the choke is open (off), it's hard to tell, because > it almost immediately stalls out and dies, so I can't tell. WIth the choke > closed, even slightly, it hovers around 1000. > OK, so one of the things that happens when the choke is operated (closed) is that it pulls the throttle open a bit, up off of the idle adjustment throttle stop. When you return the choke to the normal position, the throttle returns to the adjustment stop. The obvious answer to your problem (although it may not be right) is that you simply need to adjust the idle adjustment throttle stop screw for a higher idle speed...........to maintain that ~ 1000 without the choke.
From: mwhyte via MotorcycleKB.com on 18 Jun 2007 15:24
Ken Abrams wrote: The obvious answer to your problem >(although it may not be right) is that you simply need to adjust the idle >adjustment throttle stop screw for a higher idle speed...........to maintain >that ~ 1000 without the choke. OK, so here's an update from my fiddling that might provide further insight: This morning, I twiddled the idle mixture screws on both carbs a bit, abotu a half turn counter clockwise on each. Then, I turned up the idle adjustment throttle stop screw, in hopes of upping the idle speed directly at the throttle. The result: A semi-consistent idle around 1100 rpms, BUT the bike was seriously sluggish -- ie. had no power, and took forever to get to higher rpms in pretty much any gear. Seriously, it had less than half the torque it usually does. I thought I might have a piston out, but both tailpipes were puffing out exhaust, so that doesn't seem to be the case (I also put my hand on the engine on both sides, and could feel the pistons firing at idle.) So, no idea what the deal is now. Very mysterious. Anyone who has any ideas, I'd be grateful to hear them. Many thanks, MW -- Message posted via MotorcycleKB.com http://www.motorcyclekb.com/Uwe/Forums.aspx/tech/200706/1 |