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high rev problem

This is a discussion on high rev problem within the Yamaha YFZ450/450R (2004-Present) forums, part of the Performance /Technical category; When de engine is semi cold it revs fine. But when the engine heats up it starts to sputter around 3/4 throttle. Went in al ...


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Old 08-26-2005, 12:37 PM   #1
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Default high rev problem

When de engine is semi cold it revs fine.
But when the engine heats up it starts to sputter around 3/4 throttle.
Went in al directions with the jetting.
So I am thinking electrical.
Someone said ignition, is this possible?
Could it be the rectifier, witch is gone because the last time I checked it fried the headlights in 2 seconds.
I run without the lights.
Have a CBR battery.
Light switch on or off, no diff.
Any help would be appreciated.
Thanx..
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Old 08-26-2005, 01:20 PM   #2
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i am having the same problem at full throttle it almost feels like a rev limitor but you can tell it is not so i took the carb off and looked at the jets changed my piolet from the 42 to a 45 and now threw the hole throttle its running terrible and it seems like it wants to die throwing flames sputtering you name it this quad is not running right and i cant figure it out
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Old 08-26-2005, 02:50 PM   #3
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Could be the tps or the rectifier messing up
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Old 08-26-2005, 04:12 PM   #4
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TPS is disconnected
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Old 08-26-2005, 05:18 PM   #5
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this may sound like a stupid ? but i just bought a yfz but what is a tps
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Old 08-27-2005, 03:22 AM   #6
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Could it be the stator?
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Old 08-27-2005, 05:41 AM   #7
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Quote: Originally Posted by ex_rider
this may sound like a stupid ? but I just bought a yfz but what is a tps
TPS is a throttle position sensor.
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Old 08-27-2005, 10:44 AM   #8
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Default Re: high rev problem

Quote: Originally Posted by ronnieb
When de engine is semi cold it revs fine.
But when the engine heats up it starts to sputter around 3/4 throttle.
Went in al directions with the jetting.
So I am thinking electrical.
Someone said ignition, is this possible?
Could it be the rectifier, which is gone because the last time I checked it fried the headlights in 2 seconds.
I run without the lights.
Have a CBR battery.
Light switch on or off, no diff.
Any help would be appreciated.
thanks..
Its either something electrical or rich jetting. How far did you lean the main. An engine will richen up as it goes from cold to hot. Better atomizing of fuel. Thats why you need to choke the motor when its cold. The motor also typically richens up as the RPM's get in the upper ranges. Less of a load on the motor means that it needs less fuel.
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Old 08-27-2005, 01:43 PM   #9
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went from 172 to 185 on the main in steps of 3
48 to 52 on the pilot
yz needle clip 3 to 6
fuel screw 1/2 to 31/2 turns
cammod,drd slip-on,aftermarket intake(ronwoods style),twinair filter, no lid
so I am thinking electrical.
Alternator or stator, or something else?
Alternator is dead but I don't use the lights, but can this be the problem for the stuttering.
If there are more than 3 wires I am lost with the electrical stuff.
so help me out please.
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Old 08-27-2005, 07:04 PM   #10
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i have the same problem, you have to put the headlights back on, its a stator problem. Talk to Bob at Magnolia tractor and he will hook u up with a rectifier kit for 50 bucks. I race mx and i still have my headlights on because of this problem
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Old 08-27-2005, 09:30 PM   #11
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Quote: Originally Posted by RippinRaptor55x
I have the same problem, you have to put the headlights back on, its a stator problem. Talk to Bob at Magnolia tractor and he will hook you up with a rectifier kit for 50 bucks. I race mx and I still have my headlights on because of this problem
You mean resistor kit don't you?
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