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High Altitude Carburetor Performance
Posted: Sat Oct 11, 2014 4:24 am
by nicholastanguma
Just how flexible are the carbies on a 710? I'd like to overland a 710 through subcontinental India all the way up into the Himalayan kingdoms, where some of the "roads" reach 14,000 to 18,000 feet above sea level.
Re: High Altitude Carburetor Performance
Posted: Sat Oct 11, 2014 9:13 am
by undysworld
Flexible? Well, you can change the jets to adjust for altitude, if that's what you're asking.
Mine didn't run with any too much pep over Vail pass (10,500'-ish), but it ran okay. I only managed about 25mph uphill at some spots, and I didn't pass anyone.
We also climbed the trail up to Holy Cross City, which I believe is about 12,000', and it ran fine. But there we were all in low 1st gear. I used nearly 25 gal. in about 30 miles.
I don't have any experience with the altitudes you're looking at. Hopefully others will chime in with more info.
Re: High Altitude Carburetor Performance
Posted: Sat Oct 11, 2014 9:43 am
by Stekay
Wow, sounds like an Awesome adventure. Consider that at 18K ft, the air density is exactly half of of that at sea level. So you should pick up some smaller fuel jets after consulting a chart. (available online) Also you'll be able to advance the timing quite a bit depending on the quality of fuel available. Cooling will be greatly inhibited (at altitude) so a cylinder head and exhaust gas temp gauges would be something I would install to protect my engine. Water or alcohol injection is another option and will add some power.
Re: High Altitude Carburetor Performance
Posted: Sat Oct 11, 2014 11:38 am
by GRCameron
Do you have a link to a jetting chart? I have looked and find none. Maybe I've looked in the wrong places...
I live at ~5000 ft. and am looking at rejetting to get back some fuel economy, if nothing else. My 710M gets about 7-8 mpg which doesn't excite me in the least. I know enough to not lean it out too much, but it is quite rich right now.
Re: High Altitude Carburetor Performance
Posted: Sat Oct 11, 2014 3:13 pm
by Stekay
I'd contact Dennis Williams at
http://www.lindenengineering.com/index. ... =ContactUs he works on Pinz's and lives in Golden CO. He know "altitude" issues. You need the correct combination of emulsion tube, air jet, and main jet.
Re: High Altitude Carburetor Performance
Posted: Sun Oct 12, 2014 12:08 am
by McCall Pinz
GRCameron wrote:I know enough to not lean it out too much
. Be careful on the way back down after setting the carb for altitude and running into lean condition.
Re: High Altitude Carburetor Performance
Posted: Sun Oct 12, 2014 1:45 pm
by McCall Pinz
ps- search for "altitude" and "jets" here and you'll find a lot of info.
Re: High Altitude Carburetor Performance
Posted: Sun Oct 12, 2014 3:06 pm
by Jim LaGuardia
For above 5000' use 125 main jets and 55 running jet, set timing to 8deg BTDC.