[NSRCA-discussion] Fuel Regulation in 2C Engines

[Nat Penton]

Vicente
My experience in setting the idle on a two stroke is to continue to lean until it wont run, then richen slightly. The motor will then be instantly responsive to throttle. If you run with a rich idle you can pinch the fuel line, at idle, and the engine will continue to run, even speed up as it approaches the right mixture.                           Nat
  ----- Original Message ----- 
  From: vicenterc at comcast.net 
  To: NSRCA Mailing List ; NSRCA Mailing List 
  Sent: Tuesday, March 07, 2006 6:57 AM
  Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines


  All,

  It is evident that I had been setting the low end lean.  Next time I fly, I will adjust to get richer low end.  I don't think I am running the engine hot.  However, I am going to try to improve cooling and see if this helps. 

  Thanks to all again.  I got very good feedback. 

  Vicente Bortone




    -------------- Original message -------------- 
    From: "John Pavlick" <jpavlick at idseng.com> 

    > Jerry, 
    > Thanks for confirming my observation re- lean idle = slow transition to 
    > idle. I first noticed this on my old Arctic Cat sleds. I've always felt more 
    > comfortable with 4-strokes - I guess that comes from wrenching Harleys. I'm 
    > finally figuring these ringy-dingy 2-strokes out I guess. So who says toy 
    > airplanes aren't educational? 
    > 
    > John Pavlick 
    > http://www.idseng.com 
    > 
    > BTW - I've been using sealed bearings (seals on both sides / -2RS type) 
    > front and rear. In stock configuration, normally the front bearing is 
    > shielded on one side only - no seals. This does nothing (or at best very 
    > little) to seal the crankcase. With both sides sealed, there is much less 
    > ch! ance of an air leak that would definitely causes slow transition AND 
    > erratic idle. In extreme cases I've seen motors that wouldn't shut off even 
    > with the throttle fully closed. The fix was new bearings. 
    > 
    > 
    > 
    > > -----Original Message----- 
    > > From: nsrca-discussion-bounces at lists.nsrca.org 
    > > [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Jerry Budd 
    > > Sent: Tuesday, March 07, 2006 12:28 AM 
    > > To: NSRCA Mailing List 
    > > Subject: Re: [NSRCA-discussion] Fuel Regulation in 2C Engines 
    > > 
    > > 
    > > >5. It is clear that all 2-cycle engines will have this behavior. 
    > > 
    > > I guess I have to offer a different opinion on this. If you have the 
    > > low end set lean (and most running the OS140Rx are running the bottom 
    > > lean to get the mid-range somewhat reasonable) you will not be able 
    > &g! t; to get the motor to settle into a low idle quickly. And that 
    &g t; > presents itself as poor down line breaking, as well as the occasional 
    > > flameout. When I ran the OS140's I bought four motors and then 
    > > picked the two with the best carbs (aka midrange) so I could set the 
    > > low end where it belonged. I also used higher nitro fuel (Magnum #1) 
    > > to help lean the midrange, which also allowed me to run the pipe 
    > > about an inch longer (which helped soften the pipe "bump"). 
    > > 
    > > I had good luck (post '02 Nats) and good power (8400 rpm, APC 17x12) 
    > > with the OS's, but I found that the throttle response wasn't the best 
    > > if you used a lot of throttle to control speed. When I switched to 
    > > the Webra 160 I was able to set the top end rich and still have more 
    > > power than I knew what to do with (because of the enormous 
    > > torque/very conservative exhaust timing), and also set the idle 
    > > sligh! tly rich so the motor would quickly settle into a low stable 
    > > idle. Of course this was a lot easier to do with the MC carb since I 
    > > didn't have to compromise on the mixture settings. 
    > > 
    > > But, anyway, to bring this back to point. The most prevalent reason 
    > > for a 2c to have an erratic idle with poor down line braking is a too 
    > > lean idle and a hot motor (like Evil Eric said). Adding a fuel pump 
    > > or a pressure regulator or whatever won't fix that. 
    > > 
    > > Just my $0.02 worth, 
    > > 
    > > Jerry 
    > > -- 
    > > ___________ 
    > > Jerry Budd 
    > > Budd Engineering 
    > > (661) 722-5669 Voice/Fax 
    > > (661) 435-0358 Cell Phone 
    > > mailto:jerry at buddengineering.com 
    > > http://www.buddengineering.com 
    > > _______________________________________________ 
    > > NSRCA-discussion maili! ng list 
    > > NSRCA-discussion at lists.nsrca.org 
    > > h ttp://lists.nsrca.org/mailman/listinfo/nsrca-discussion 
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