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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Lbxpdx on July 03, 2023, 12:50:16 PM
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Hello all. So this is my first k bike, a 92 K75rt with 105k miles. The original owner had the bike up to 103k and the PO maybe rode 1.5k in 2 years. I have a stack of paperwork and a book full of service stamps.
I have only ridden it 100 miles so far, so I may be premature in my questions. The bike runs great. Idles around 1250, had the throttle bodies snyced 9k ago, fuel filter replaced, air filter, and some other stuff. The PO had non ethanol in it when I bought it and I have put non ethanol in it too. I should add that the 9k was 9 years ago.
The air filter looks clean, the tank looks clean, I checked the tb sync with my twinmax and they are spot on.
Ok, so above 5k the bikes feels throaty, not smooth and linear like it does up to 5k. Is this a k thing, or should it feel smooth all the way up.
What would cause the bike to not feel smooth above 5k? Fuel or air?
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should feel smooth all the way to redline. I'd suspect fuel filter first, possible to get clogged from one bad tank. Water in bottom of gas tank is possible from not getting much use the past 2 years. When were the valves last checked? Coils, plugs and plug wires are possible but less likely imho.
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Valves were done 9k ago.
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Leaks in rubber intake components can cause performance to slump during high demand. A frequent culprit is the z-hose running from the crankcase left of the throttle bodies to the air box. The intake manifolds attached to the crankcase can also crack and leak. Start the engine, set the revs at 4000 then spray the z-hose and the manifolds with carb cleaner or propane gas. If the revs rise, they've got leaks. This is a simple procedure. Do the z-hose first. Don't light yourself up by misdirecting the spray. :laughing4-giggles:
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Everything Laitch said. 9k miles was a long time ago. At this point, any original rubber hose is very suspect (intake, fuel and brake). Time for a lot of replacement.
Btw - the idle is too high. Should be 900ish. That is a clue that engine work is needed.