[NSRCA-discussion] Fuel Regulation in 2C Engines

[vicenterc at comcast.net]

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 
> chance 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 
> > to get the motor to settle into a low idle quickly. And that 
> > 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 
> > slightly 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 
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