Altitude Correction Plug

[MEZ]

Hi all,     can someone who know's where the altitude correction plug is on there US k75 please pull it off the bike and measure the resistance across it for me. I'm hoping it's a straight shorting wire/plug and not a set resistance...???? Thanks

[The Mighty Gryphon]

it's just a loop of wire.  Essentially zero resistance.

[alexg]

Hi:
getting back into the bike. Can you please explain where this altitude plug plugs? I am planning to go to SLC, and will be riding at 8000 feet elevation.

Thanks,

Alex

[The Mighty Gryphon]

The socket for the high altitude plug is located on the left side of the bike.  It comes out of the harness above the coils.  It might be hidden behind the left side battery cover.

[The Mighty Gryphon]

I wouldn't worry too much about the plug.  I have ridden over 9,000 feet without it and down to a couple hundred feet above sea level with it plugged in and never really noticed a difference in performance. 

The MAF does a pretty good job of adjusting for altitude since lower air density results in less deflection of the door, thereby automatically correcting the mixture.  I suspect, but can't prove, that the only purpose of the high altitude plug was to appease the EPA bureaucrats who were still living in the days of carburetor main jets and the richer mixtures they produced at high altitude.

[alexg]

Mighty:
as always, your theory makes sense. I will not worry about it.

Thanks

Alex

[K1300S]

just for reference...these bikes do not have an MAF.  they have an AFM.  not the same.

[K1300S]

the altitude plug does make a small difference.  ez to find and simple to make a loop of wire across the terminals.  basically grounds a pin in the ecu to change the mixture a touch for the thinner air.

[MEZ]

Ok, straight connection, good.

A further question now, rightly or wrongly, I have simulated the jumper plug using a switch on a post 1990 loom/engine going by wire colours but do the post 1990 bikes use a different ECU and fuelling system..??

[The Mighty Gryphon]

Both of my 1994 K75's had altitude plugs. 

Back when I obsessed over it, I thought about having someone build a small Arduino(sp) device to automatically switch the connection at 4000 feet.  I have seen them and they look to be pretty simple and not too expensive to build.  Riding in the Rocky Mountains I can go up and down through 4000 feet 5 or 6 times a day, sometimes more, and it turns into a PIA to watch the altitude on my GPS and stopping to screw with the plug so it seemed like a good thing to have.

But after riding to the top of Pike's Peak without the plug on 87 octane fuel and not experiencing any pinging or performance issues I sort of decided that the plug isn't all that important.  I still carry one just in case I need it, but haven't used it in a few years now.

[Laitch]

, . . .  do the post 1990 bikes use a different ECU and fuelling system..??

The post-1990 K75 Bricks use the same system as the pre-1990 2V models—the Jetronic. The four-valves models from 1990 onward use a different fuel management system—the Motronic.