[NSRCA-discussion] Fuel Regulation in 2C Engines

[John Pavlick]

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
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.375 / Virus Database: 268.2.0/275 - Release Date: 3/6/06
>
--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.375 / Virus Database: 268.2.0/275 - Release Date: 3/6/06