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I have a 2008 kfx450r and it’s carbureted and everything and I have a rattle in the front end at least it sounds like the front and I can’t figure it out please help also I have a rattle in the motor when I’m on a hill or something and punch it I get a strange knocking noise any one know what it could be
 

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Thanks dust but how do I figure out that they are going bad and now when I take off on a hill it almost feels like it’s jerking and the whole motor shakes I’m so lost and I’m tired of putting money into this damn thing
 

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Thanks dust but how do I figure out that they are going bad and now when I take off on a hill it almost feels like it’s jerking and the whole motor shakes I’m so lost and I’m tired of putting money into this damn thing
Does it jerk & shake in every gear when you get on it...???..or only a certain gear...If only a certain gear than you might have a broken gear tooth...

Have you drained the oil into a strainer to check for metal shavings...???

But if the knocking sound is heard in the lower motor area then you'll have to pull the motor apart to check it...or at least remove the cylinder and inspect the crankshaft...
 

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No the only time I have noticed it is when the quad is really cold it jerks and cold the crankshaft be just the bearings for the case because I really don’t want to buy a whole new crank and I was thinking could the sound be the valves because I can’t exactly pein point where it’s coming from because I’m all ways on a hill or something whim it does it and the bike was just carb converted cold that have anything to do with it??
 

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No the only time I have noticed it is when the quad is really cold it jerks and cold the crankshaft be just the bearings for the case because I really don’t want to buy a whole new crank and I was thinking could the sound be the valves because I can’t exactly pein point where it’s coming from because I’m all ways on a hill or something whim it does it and the bike was just carb converted cold that have anything to do with it??
Try adjusting your carb for running lean air/fuel mixture to prevent the jerking when climbing hills...or have the carb re jetted for a proper air/fuel mixture if your running an upgraded intake such as a Fuel custom Intake system....see picture (FCI vs Stock)

If it's only when the motor's cold & under extreme load on the motor....then it's probably the valves ticking...Not sure without hearing it myself to make a proper diagnosis...???

If the main bearing were knocking you would loose a lot of the performance whether the motors Hot or Cold...It's sounds like a hammer pounding inside the crankcase...!!!
 

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Discussion Starter #8
Hey dusty it’s me I’ve done a lot to it and it’s been running good but now I have a new piston and valves and it does start right it’s hard to start sometimes have to pull start it I’ve tried everything I can think of do I need to shim the valves again since it hase some hours on them
 

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Check tps. It might be a little out of spec

Definitely check valve lash.

Also, turn the idle speed up a little. It might be a little low.

What ecu are you running?
 

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Well I just pulled my valve cover off and checked timing it was off so I put it in time she fired right up and I took it for a ride to make sure it was all good got back to the house I stalled it and it jumped time wth could be making it do that I put new valves in it with stiffer springs could that be the problem what should I replace first the chain or what the chain does look pretty stretched I bought the quad used but ever since I got it I probably put about 60 hours on it
 

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New oem chain and tensioner!
Tensioner might not be working correctly
 

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Man I just can’t get a break my kfx is carb converted but new valves and piston in also have a coustom intake on it with lots of air flow and I have a dead shorty exhaust what should I set my valves at and also the bike is bogging really bad from idle and the. Will cut out and almost loose all loved at full thoutle please help
 

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Man I just can’t get a break my kfx is carb converted but new valves and piston in also have a coustom intake on it with lots of air flow and I have a dead shorty exhaust what should I set my valves at and also the bike is bogging really bad from idle and the. Will cut out and almost loose all loved at full thoutle please help
Here's the valve clearance spec's...

Valve Clearance: between cam and valve lifter
Standard:
Exhaust 0.17 ∼ 0.22 mm (0.0067 ∼ 0.0087 in.)... best is 0.21mm
Inlet 0.10 ∼ 0.15 mm (0.0039 ∼ 0.0059 in.)... best is 0.14mm
If the valve clearance is not within the specified range,
adjust it.
 
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