Author Topic: Rough running k75, bad air-fuel mixture  (Read 13727 times)

Offline Smackover

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Rough running k75, bad air-fuel mixture
« on: May 13, 2012, 05:07:44 PM »
I have a 1994 K75.  Last week after I stopped in the parking lot I clumsily set my K75 down on it's right side while at the same time revving the engine since my hand was firm on the throttle.  No damage to the bike, as I was standing still.  I picked the bike up and parked it there for the rest of the day.

When I was leaving to go home, about a 30 minute drive, the engine was running a little rough, and by the time I made it home it was puttering a long pretty sad.  It seems like it is starving for air.  It is firing all all 3 cylinders I can tell from after letting it sit for a day or so it runs fairly smooth at idle.  Also, parked in my garage I can tell that the exhaust smells very rich, telling my I'm not getting a full burn of the gas going into the cylinders.

Could I have messed up the air filter, air intake system, or the fuel filter or even the spark plugs that would cause my K75 to gasp for life?

Thanks

TrustFundManChild

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Re: Rough running k75, bad air-fuel mixture
« Reply #1 on: May 13, 2012, 05:43:36 PM »
If you decide to dismantle it please let know.  I can always use some more parts in my machine shed.

Offline frankenduck

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Re: Rough running k75, bad air-fuel mixture
« Reply #2 on: May 13, 2012, 06:09:21 PM »
You may have knocked your TPS out of adjustment somehow.  It's the black plastic thing at the rear of the throttle bodies.  With the bike turned off you should be able to hear a small click from it right you when start to apply throttle.

It tells the L-Jetronic (FI) computer that you're at idle and the engine gets less fuel.  If you don't hear that click then loosen the two screws that hold it and reposition it so that it clicks when you come off idle.  Then tighten down the screws.
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Rick G

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Re: Rough running k75, bad air-fuel mixture
« Reply #3 on: May 13, 2012, 07:41:22 PM »
Other than the TPS I can think of what it would be.It could be the Air flow meter having been knocked so that it isn't working correctly but they are fairly well protected. If anything else to do with the air/fuel system was disloged it would most likely run lean or not run at all.

Offline johnny

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Re: Rough running k75, bad air-fuel mixture
« Reply #4 on: May 13, 2012, 09:33:27 PM »
greetings smackover...

welcome to the world famous motobrick.com...

id take that moe out on a long straight flat and red line it through the gears and keep it there till i ran out off road... if that wont fix it nothing will...

j i
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline Smackover

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Re: Rough running k75, bad air-fuel mixture
« Reply #5 on: May 14, 2012, 12:51:39 PM »
Update:  The TPS is adjusted and properly functioning as described, but still have issues.  I haven't got to the air flow metering adjustments yet, but plan to do that next.  I don't think I could red line it if I wanted to.  It bogs down and peaks out between 5-6k rpms no matter how much throttle I give it.  But that's after I'm already rolling, so if I start in 1st at redline it might hold through the gears.

More on how it's running, quick throttle movements choke it out and kill it occasionally.  After it's warmed up it runs worse, chugging along at 5-6k rpms.  It idles fine, but adding any throttle is asking too much; mixture of small backfires, knocking, and running choppy.

Thanks for your help, and I'm looking into ways to adjust/check the air flow metering.


Offline mystic red

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Re: Rough running k75, bad air-fuel mixture
« Reply #6 on: May 14, 2012, 12:56:05 PM »
I hate to sound like a broken record......but this is what it sounds like.

Get a propane bottle out and start lookin'. Far less messy and way more precise than starter fluid.

Offline johnny

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Re: Rough running k75, bad air-fuel mixture
« Reply #7 on: May 14, 2012, 01:31:18 PM »
i knows it aints sounds like a gass filter butts the bugg did the same thing once and it was a clogged gass filter...

j o
  • :johnny i parks my 96 eleven hundert rs motobrick in dodge county cheezconsin  :johnny

Offline mystic red

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Re: Rough running k75, bad air-fuel mixture
« Reply #8 on: May 14, 2012, 05:05:53 PM »
i knows it aints sounds like a gass filter butts the bugg did the same thing once and it was a clogged gass filter...

j o

+1 on that, too. Start with the easy stuff and work your way thru it.

Offline Smackover

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Re: Rough running k75, bad air-fuel mixture
« Reply #9 on: May 17, 2012, 11:08:29 AM »
Problem solved.  So I think I figured out that it had to do with the fuel flow rather than the air flow.  However, even after I changed the fuel filter it didn't fix the problem so I think all the junk in the tank that got stirred up when I laid it over clogged up the mesh filter on the fuel pump as well.  My rudimentary solution was to lay the bike on it's left side (since I laid it over on it's right before) and that actually cleared things up enough to run normal.

I am going to do a more thorough cleaning of the gas tank once I get the gas level down to where I can drain it into my gas can.  Thanks a lot for your help and advice.  I'm fairly new to the brick and feel like I've learned a lot from this experience.

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