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epremack


Joined: Feb 24, 2011
Points: 8

Difficult to swap-out hi-altitude carb jet in Honda motor?
Original Message   Aug 9, 2011 11:27 am
I just bought a pressure washer powered by a Honda GCV190 motor.  I bought it at sea level, but recently brought it to 6,200 feet altitude.  It seems to run well at 6,200 feet, but I wonder if I'm either damaging the engine or running the risk of fouling it?

Honda makes a couple of inexpensive (<$10) substitute carburetor jets for higher altitude.  The manual says to bring the unit to a Honda dealer to substitute the alternate carburetor jet. 

I'm wondering if (1) I should bother with switching the jet and, if "yes," (2) whether it's an easy switch that I could perform without hauling the unit back and forth to the dealer?

I'm mechanically inclined and have good tools, but have never done anything beyond minor services (e.g., changing/gap-ing the plug, changing oil, and changing/cleaning air filters) on small engines.  Does anyone have experience making this switch?

Thanks.  
Replies: 1 - 8 of 8View as Outline
carlb


Joined: Nov 16, 2010
Points: 279

Re: Difficult to swap-out hi-altitude carb jet in Honda motor?
Reply #1   Aug 9, 2011 2:46 pm
They are very easy to replace.  You wont damage your motor if it is a little rich, but you can pull the spark plug after running it at load for a bit and see if it is black/sooty or not.

To replace the jet you just take the bolt out of the bottom of the bowl and then take the proper size straight blade screwdriver and stick it up the whole that the bowl blot was in.  The jet in at the top of that tube.  Just unscrew the jet and remove it.  You may have to tap the tube on the side to get the jet to fall out.  Then just stick the new jet in the whole and screw it in.  There is an emulsion tube that sits above the jet and that may fall out when you take the jet out.  You can just put back in place then put the jet in.

Carl
This message was modified Aug 9, 2011 by carlb
epremack


Joined: Feb 24, 2011
Points: 8

Re: Difficult to swap-out hi-altitude carb jet in Honda motor?
Reply #2   Aug 9, 2011 9:34 pm
Thanks carlb.  Very helpful.
phatline


Joined: Sep 28, 2012
Points: 2

Re: Difficult to swap-out hi-altitude carb jet in Honda motor?
Reply #3   Sep 28, 2012 5:17 pm
We just bought an HS928TA from our dealer in California. Dealer and our house located at 6400 feet.
I asked them if I need a high altitude jet (as per Honda manual, page 69) and, depending on the individual asked, they responded with:

* "No" (no reasoning)
* "Honda ships it with the jet it needs" (sounds reasonable... but somehow I doubt this)
* and my favorite: "That's silly--it only snows at high elevations."

I prodded and they said they can order main jet Mark 80, 82, or 85. But they have no idea which one would be appropriate for our altitude. I couldn't get through to anyone at Honda.

Does anyone here know (a) if Honda really does ship units with the proper jet for the dealer elevation, and if not, (b) how to pick the right size? I think I can install it myself but I don't know which jet to get :(.
This message was modified Sep 28, 2012 by phatline
robertcoats


Joined: Dec 12, 2011
Points: 39

Re: Difficult to swap-out hi-altitude carb jet in Honda motor?
Reply #4   Oct 1, 2012 12:49 pm
For Honda stuff, all products, including snowblowers, are shipped with a "standard" (0-5,000 ft) suitable jet. In this case, it's a #85, which, as I recall, at least for Honda, = 0.85 mm inside diameter.

Exceed 5,000 feet and the reduced oxygen will cause the mixture to be rich (too much fuel) and you might see a black or sooty spark plug.

For a fix, install the next size smaller jet, such as a #82. This will reduce the fuel and make the mixture correct for the amount of air above 5,000 feet. Note this will also reduce the power a bit, but not much you can do about that. At least the mixture will be correct and you won't foul or have to replace a plug too soon.

Eventually, fuel injection would solve this, but for now, if the snowblower is routinely going to be run above 5,000, and you see evidence of a fouling or black spark plug, for sure change the jet.

FYI, note the emulsion tube held in place by the jet; it only goes back in one way, so pay attention as it drops out with the jet.

-Robert@Honda

Caveat: I work for Honda, but the preceding was my opinion alone.
This message was modified Oct 1, 2012 by robertcoats
friiy


Location: Las Vegas, The Desert
Joined: Apr 12, 2008
Points: 600

Re: Difficult to swap-out hi-altitude carb jet in Honda motor?
Reply #5   Oct 1, 2012 9:38 pm
Atmospheric pressure changes, not the oxygen level with altitude...   The engine will have greater reduction of HP if you don't change the jet... The engine should lose about 3% HP for every 1K of altitude if the jetting is correct... If the jetting is incorrect you lose additional HP...

Be sure if you run this unit at a standard altitude to change the jet back to original,   too lean of a jet setting can burn valves and piston head over just a short time ..

Friiy

phatline


Joined: Sep 28, 2012
Points: 2

Re: Difficult to swap-out hi-altitude carb jet in Honda motor?
Reply #6   Sep 22, 2015 2:31 pm
I forgot to check back for replies. Thanks folks! I just ordered a Mark 82 and will try that out. I haven't seen fouling of the plug but we also haven't had much snow. I've barely got 20 hours on the machine in the last few years. It's a real shame that our dealer here has no clue about this part. It probably means all of the thousands of Honda snowblowers running in our area (6200' and up, Lake Tahoe) are burning rich. Given the service life of a Honda I expect all of their emissions controls are long gone!
epremack


Joined: Feb 24, 2011
Points: 8

Re: Update and new carb question.
Reply #7   Sep 27, 2015 1:57 pm
I was the one who posted this question back in '11 and offer thanks for the advice and updates. I opted to leave the original jet in the carburetor for my pressure washer. While I don't use it often, It seems to work fine at 6,200'. What little fouling of the plug I experience likely comes from the tablespoon of oil that I put into the cylinder when I store it a few times each year. I also have an older Honda HS928 snowblower. I don't know what jet it has (I'm the second owner), but it too seems to run pretty clean. The carburetor on the HS928, however, is now leaking fuel--so I've emptied it but need to get ready for El Nino. I believe it's leaking from either the top of the float chamber or the sediment cup. It's hard to tell where. It runs well for an old and heavily-worked machine, with only intermittent hunting if I use fuel that's a bit stale. I presume it needs fresh gaskets. I noticed that the Honda OEM gasket set costs around $13--about the same price as a whole aftermarket carburetor. Does anyone have experience with these aftermarket carbs? Are they and/or the aftermarket rebuild kits any good? Or should I simply spring for the $13 gasket set and clean out the old carb? I'm not a small engine expert by any stretch, but do generally change my own oil/plug changes and rebuilt the front end of this blower when I bought it back in '11.
carlb


Joined: Nov 16, 2010
Points: 279

Re: Difficult to swap-out hi-altitude carb jet in Honda motor?
Reply #8   Sep 28, 2015 7:28 am
Since the EPA forces all engines used in the states to run very lean because of their regulations you are probably fine with the larger jet.  As mentioned above run the engine under a load for a while pull the spark plug and see what it looks like.   There are many pictures on the web of what the plug on a properly jetted engine  should look like.
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