Kx450 problems

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7/20/2018 3:57 PM

Thought id try here one last time before cutting my losses and getting rid of this bike. Currently it starts and runs as long as you want. Once its hot and you turn it off it wont restart till it cools. Ive had the bike randomly die on me a couple times after its hot too. Ive replaced about half the electronics on it.

Replaced parts:
Main harness(not the harness that goes to the throttle body sensors and temp sensors)
Ecu
Coil
Spark plug cap
Spark plug
Kill switch
Capacitor
Tip over sensor
Fuel pump

Spark plug is dry when i pull it out and the tip is tan.

So far the stator ohms okay. .5/.6 is where the leads are when its hot. Manuals range is .5-1.1 ohms.

My plan is to fix this bike and sell it. For whatever reason its been absolutely terrible all year. Any help or guidence is appreciated. My kawi dealer is even lost.

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7/21/2018 8:08 AM

Alright guys so i got skeptical about this being an electrical problem so i did a leak down test. Somehow with 2 hours on a NEW head and NEW valves and NEW cams its got an 80% leak on one of the intake valves. The leak is loud as hell when i open the throttle. Not much of anything on the exhaust or crank vent.

So what now? I have stainless valves from prox. Will lapping the valves fix my problem? Worth a try? I know you cant lap titanium but wasnt sure about stainless.

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7/21/2018 8:28 AM

kb228 wrote:

Alright guys so i got skeptical about this being an electrical problem so i did a leak down test. Somehow with 2 hours on a NEW head and NEW valves and NEW cams its got an 80% leak on one of the intake valves. The leak is loud as hell when i open the throttle. Not much of anything on the exhaust or crank vent.

So what now? I have stainless valves from prox. Will lapping the valves fix my problem? Worth a try? I know you cant lap titanium but wasnt sure about stainless.

With that few hours, I’m guessing either a guide was out of alignment and/or there’s a seat/valve issue. I’d yank the head and look.guessing it’s going to be obvious.

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7/21/2018 8:29 AM

Was the leak down done hot or cold? With that much leak down cold I don’t see how you’d ever get it lit.

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7/21/2018 8:36 AM
Edited Date/Time: 7/21/2018 8:55 AM

Its a cold leak down. And yeah the bike fires up in 4-5 kicks cold. Wont start hot though.

I was thinking the same thing too. I either have a defective head or valves or maybe carbon is holding it open.

I rebuilt a kx250f about the same time with the same parts but didnt run into any issues like this.


Also, my dumbass had tdc off by 180 degrees causing it to read 80%. Cold leakage is 20% at the correct tdc. Thats still high though. 5-10% is what ive always been told is good

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7/21/2018 9:34 AM

Were the valve seats cut when the new valves were installed?
Were new valve guides installed?
Were new seals installed?
You can't lap those valves.

Paw Paw

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7/21/2018 1:58 PM

Paw Paw 271 wrote:

Were the valve seats cut when the new valves were installed?
Were new valve guides installed?
Were new seals installed?
You can't lap those valves.

Paw Paw

The head and valves are new. The seats and guides are installed by kawasaki.

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