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Old 06-18-2014, 09:05 PM   #1
Failo OP
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BMW K75 Low on Power after new fuel lines

My son just bought a seemingly nice 88 K75S but broke down on his first ride when one of the plastic fuel line quick connects broke. We replaced both fuel lines with new 5/16" fuel injection hose, eliminating the quick connects.

Although the repair seemed pretty straight forward, he says the bike has no power and needs to be choked to start, no matter how warm the engine is. He says when upshifting he has to rev the engine and feather the clutch to keep the engine running.

The only thing I can think of is that maybe we pinched the vent line coming off the bottom of the tank when we reinstalled the gas tank.

He's holed up in Steamboat Springs after only traveling 160 miles today and I've advised him to sit tight until he gets this figured out. He's headed up into some pretty desolate parts of Wyoming and Montana, and Dad is worried.

Any ideas on how to troubleshoot this?
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Old 06-18-2014, 09:48 PM   #2
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If a vent line is pinched usually you will have full power until a vacuum is created in the tank. Loosen gas cap to check..

I think some debris has come off the old lines and gotten into the carburetor(s). Pull the float bowls and gently clean the jets with computer duster and possibly carb cleaner spray. When you look in the bowls you will find debris. Don't just throw that gas out. Inspect it first.


Good Luck.
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Old 06-18-2014, 11:36 PM   #3
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Quote:
Originally Posted by spafxer View Post
If a vent line is pinched usually you will have full power until a vacuum is created in the tank. Loosen gas cap to check..

I think some debris has come off the old lines and gotten into the carburetor(s). Pull the float bowls and gently clean the jets with computer duster and possibly carb cleaner spray. When you look in the bowls you will find debris. Don't just throw that gas out. Inspect it first.


Good Luck.
Carburators???

K75S has a vacuum fuel pressure regulator, I'd look at the vacuum line to the regulator for cracks or leaks.It is behind the throttle bodies and may be hard to see without removing the airbox.And at the same time a look at the vacuum port plugs.
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Old 06-18-2014, 11:43 PM   #4
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Sorry for that reply.. I was thinking the Boxer R engine ....


Still would say it's plugged injectors or filter or... Some reason it's running lean now and wasn't before the hoses were replaced.
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Old 06-19-2014, 09:48 AM   #5
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Sorry for that reply.. I was thinking the Boxer R engine ....


Still would say it's plugged injectors or filter or... Some reason it's running lean now and wasn't before the hoses were replaced.
That's ok....doesn't take much to plug them old Rs, little piece of crap floating around the bowl and plugging the jet can drive you nuts the first time.

Back to the K, they are well known for the rubber bits inside the tank turning to goop after sitting too long and that was even before the Ethanol days. That sure can plug things up. And the fuel filter, same as my K1200RS and I have been finding them almost plugged two years in a row at way less than the recommended interval for replacement.

We don't know the bike's history but I sure wouldn't ride one of them old Ks any distance before giving it a full service of the fueling system and a very good inspection of the components inside the tank. I backflushed the injectors on my bike last winter on the odd chance the inlet filter screens could have dirt in them, nothing came out but I sure feel better....

Fuel filter on the chance that's what it is...Napa 3032 or Wix 33032 will do and easy to find.
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Old 06-19-2014, 02:46 PM   #6
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Was the bike running fine before the quick disconnect failure?

Fuel filter plugged is a good possibility. Also, the fuel filter may have split or is allowing fuel back into the tank because of bad hose inside the tank. Hoses in the tank are immersion FI type BTW.

Check the plugs; they may be fouled. Replace them if so.

Recheck the connection to the ECU under the tool tray. the big multipin connector may have dislodged. Reseat it and make sure it is fastened securely.

Recheck the fuel pump connector on the left side of the tank. These have a tendency to fail to make a good connection. Squeezing the female connections inside the housing can offer temporary relief of a poor connection.
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Old 06-23-2014, 07:28 AM   #7
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4 days? Got to be back on the road by now?
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Old 06-23-2014, 11:09 AM   #8
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I had some electrical gremlins when I had my K75. A good cleaning of all connectors and ground points helped. But, those issues were all go/no-go for me; I never experienced lean running conditions. There's a small chance that installing or removing the high altitude electrical plug could help. Good luck!
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