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Small Engines (Lawn Mowers, etc.)/Snow Blower High Altitude Jetting


Hi, Eric.

Just purchased a Honda Snow Blower HS520AS from my local Honda dealer here in Denver.

I have a question about jetting and high altitude. The manual states above 5000ft (I am located @ 5150ft) the carburetor should be jetted for higher altitude.

I told my local shop to change out the jet to the high altitude one when I purchased it. I came back to the shop, they stated they did and had my old jet in a Honda bag.

I think the shop did change the jet, however the new jet they put in is the same as the jet they took out.

The Honda Part # of the jet they put in according to the invoice is; 99101-1240700 and the invoice says SZ-70. I looked at the old jet with a magnifying glass and it has a little star and 70 printed on it.

What will happen to the engine with the improper jet installed? Actually Honda ships all there snow blowers with the 70 jet installed.   

Does it run lean or rich? What are the effects?

According to Honda's website the engine is a GC160.

Eric, thank you for any help and also the time you take.


As long as it runs good and has power at your altitude there is no problem running the standard jet...the engine will just run a little richer.  This just means more fuel so the engine will not be as efficient (fuel consumption)and may not make as much power but this is not noticeable with most power equipment.  Richer mixtures have positive attributes as the engine will run a tad cooler but again this not noticeable in most applications.

When we get snow (south of you) we sell a lot of blowers.  Rarely do we change jets and we have customers who use their blowers in the 6300-6700ft range.

As long as the engine has good power to move the snow I'd leave the 70 jet in the engine.


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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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