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Discussion Starter · #1 ·
If so, I have an EFI question on the KFX 450R

Background:
Bike never had a smooth idle
Bike stalls out super easy
Bike is an absolute stall queen
Stalls easy at take-off, or slow or technical speeds
Stalls with no warning, like an ignition cut at times
IT IS NOT ME!!!

Idle got way worse... to the point of unreal terrible.
I crawled the bike over at home and checked all a guy can check at home.
(can't fully test temp or pressure related stuff at home)

Items found:
Plug looked rich (replaced)
Crank sensor did not ohm out in range (resistance too low)


At this point I took the bike to the shop. They crawled it too, and exhausted everything... to the point they gave up, put it back together... and the problem seemed pretty much solved by accident. Still real weak off the bottom and idle still not perfect... but enough better I was really happy.

It was assumed to be a bad connection.
Bad connection at the crank sensor inside the case? (I don't know)
Crank sensor did ohm out in range when I brought it home.

Now:
After bringing home, in time it has slowly degraded. It's a stall queen again, but not back to idling as bad as before.

Since I have tried dropping a tooth in front... makes it stronger of course, but it's still a stall queen, and the lower gearing only magnifies the fact there is a problem... and magnifies the sense that it's like an ignition cut.

Adding a pipe and removing the air box lid seems to help it a lot. But I am not sure if that is purely from power gain, or if it is more about an improved air/fuel ratio. The plug still looks on the rich side.

I have crawled it again, and again I find that the crank sensor does not ohm out in range. In fact the resistance is lower than before. I've checked it several times, and have found it barely in range once when checking hot? Dunno why that would happen.

Theory:
I assume the crank sensor is bad, or has bad wiring or connection. With that I am GUESSING that possibly the ECU is reading a faulty signal from the crank sensor and incorrectly adjusting ignition timing and fuel metering.... and maybe crank sensor sometimes fails to send a signal or the 22 pulses the ECU expects, which would cut ignition.

Am I way off base here?
There is not much left right?....
One of those sensors I can't test (already shop tested though) or a faulty ECU... Right????

Everything else checks out...

Roll sensor zip tied in place
Grounds look good
TPS
Coil
Rectifier
Injector
Etc

It all seems to spec out...

I'd just like to have a more solid understanding before I take it back in a second time. I know there will be some reluctance to change a crank sensor under warranty since it requires a complete stator assembly. I don't want to return it with the same suggested problem again if it is not the problem... or cause a claim that doesn't get me fixed. All I want is to get whatever the problem is FIXED.
 

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dirt, debris, trash...........

Check all your fuel system for cleanliness. Could be something in the fuel pump that shouldn't be.
 

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This is going to sound silly but the EFI's seem to be bad about this... You sure the plug isn't fouling from being to rich at low rpm's... It will run fine at higher rpms but constantly shut off at random and run like crap off idle.

This would explain why it fixed for a short period of time... I'd take some fuel out of idle and just off idle and see if that helps any.

Grizzly 700's are pretty common for this issue even so much that they have a service bulletin at the dealers to take out fuel on the bottom end.
 

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Discussion Starter · #4 ·
Check all your fuel system for cleanliness. Could be something in the fuel pump that shouldn't be.
Well, I took the injector out just to check and clean it, and it was fine.
Fuel tank is fine too.

I did not take out the fuel pump though.
I have to assume the shop checked and pressure tested it.

That's the thing with one being in the shop... you have to assume a lot...

According to the service manual it's not serviceable for cleaning or fuel filter changes.
I'm sure it can be taken apart and cleaned somehow though?
 

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Discussion Starter · #5 ·
This is going to sound silly but the EFI's seem to be bad about this... You sure the plug isn't fouling from being to rich at low rpm's... It will run fine at higher rpms but constantly shut off at random and run like crap off idle.

This would explain why it fixed for a short period of time... I'd take some fuel out of idle and just off idle and see if that helps any.

Grizzly 700's are pretty common for this issue even so much that they have a service bulletin at the dealers to take out fuel on the bottom end.
No, that doesn't sound silly at all to me...
Sounds pretty darn logical to me.

See, this would be way worse like it was when I took it to the shop before, if I put the stock exhaust back on and left the airbox lid on. It's a 50/50 chance it's air/fuel ratio related... the other side of it being the possiblity it's just extra raw power.

But my bike has to be very rich stock... to run full exhaust and no airbox lid and not need a fuel controller. But I do not think the rich condition is normal.

I think something is causing it because others are not complaining of this.
And I would think it has to be sensor related or ECU related.

And I do not know if the fuel metering from the ECU is done with data on throttle position AND engine RPM (TPS & Crank sensor) or just throttle position. Likewise on the ignition timing curves.

And I don't know if a good air/fuel ratio can seem rich from ignition timing that is a bit off.
 

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Discussion Starter · #6 ·
And here are some reference pictures I took and kept...

Of the plug condition stock...
And of the exhaust port on the head when I took the stock exhaust off...
 

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Discussion Starter · #7 ·
And here is what the plug looks like with full exhaust... air box lid on...
 

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Discussion Starter · #8 ·
Oh, and if it helps at all, here is a picture of the stator/crank sensor assembly.

(arrow pointing at where I test from)
 

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Discussion Starter · #10 · (Edited)
Stops... there is never any saving it... happens too fast.

You can hear it miss though.

But when I say stall... it STOPS... sometimes like an ignition cut, like you hit the killswitch.
 

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check..........

Ok.......Have you checked the charging system...


(voltage regulator)........make sure its charging.........Start the engine........turn on the lights.....rev the engine from normal idle......see if the lights get brighter........Battery ever been low?

Check the starter cable connection @ the starter...........
Check the battery post connections........I have seen a battery with a short inside cause this...........Has it always started with the battery ok?
 

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Discussion Starter · #12 ·
Ok.......Have you checked the charging system...


(voltage regulator)........make sure its charging.........Start the engine........turn on the lights.....rev the engine from normal idle......see if the lights get brighter........Battery ever been low?

Check the starter cable connection @ the starter...........
Check the battery post connections........I have seen a battery with a short inside cause this...........Has it always started with the battery ok?
Yeah, I jumped on that first because I was having some battery issues.
I thought I had an over or under charging issue.

At random from one day to the next I would have a dead battery.

Everything seemed to check out though. Good voltage at the battery when checked running. Good voltage and the regulator/rectifier checks out best I can tell too. That's not to say there is not a short inside the battery though. I wouldn't know.

In the end, after talking to a lot of KFX owners, and trying a lot of things... there is a drain somewhere in the system from the factory. I park it IN gear now with the kill switch ON at all times, and I have not had it fail to start since.

I do not know why, or what causes the drain otherwise.
Must be to do with the thumb kill switch or the gear position sensor.
But both work properly... so they must be incompatible circuits or wired wrong.


I could be off base there though, and there could be some sort of short going on.
All I know is the battery drain issue is fairly common.
 

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Discussion Starter · #13 ·
The Yamaha guys say their EFI 700cc engine has done this in the Grizzly and Raptor.

Crank sensor or injector has been the cause on those.

As a Polaris owner also, I can just imagine an automatic Grizzly stalling on take-off.
That's literally how easy this 450R stalls at times.
Because as I was telling them, I can't even let my clutch out until it so slightly starts to grab.
Not without a stall... it has to be over-revved before the clutch can be let out any.

I'm going to double check my injector tomorrow, and then call for an appointment.
 

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short

That short or power drain has to be the problem .........and probably has been since day one. When this short happens its lowering the voltage on the ignition system or causing a direct loss of power to it.

Check the ignition switch for on /off continuity.
Check every fuse holder for looseness or short.
Check every wire and connection you can see and look for any sign of damage from rubbing, cuts, melted appearance, etc.. Look at hot spots around the engine and exhaust for any wires too close that could have damage from heat or movement of parts.
Make sure the battery post (+) is not shorting on anything.

One trick I've found on locating shorts (including ignition) is to move all the wires in the dark and watch for sparks. (with the ignition switch on)

Hope this helps in some way..........
 

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Discussion Starter · #15 ·
That short or power drain has to be the problem .........and probably has been since day one. When this short happens its lowering the voltage on the ignition system or causing a direct loss of power to it.

Check the ignition switch for on /off continuity.
Check every fuse holder for looseness or short.
Check every wire and connection you can see and look for any sign of damage from rubbing, cuts, melted appearance, etc.. Look at hot spots around the engine and exhaust for any wires too close that could have damage from heat or movement of parts.
Make sure the battery post (+) is not shorting on anything.

One trick I've found on locating shorts (including ignition) is to move all the wires in the dark and watch for sparks. (with the ignition switch on)

Hope this helps in some way..........
You may well be right. And I will follow up assuming you are.

A few things do confuse me though....

One is why I have no battery drain if I stop in gear and shut it off with the key. If I turn the thumb kill off, it drains. And I am pretty sure it drains if shifted to neutral, regardless of thumb switch position. Not positive but...

And if the drain is not present then, how is it when it's running in gear?
(oh.... but we have turned the key on huh?) :blush:

Forgive me, I'm not real bright on this stuff.
Turning the key on is like opposite state of the safe state I'm parking in?


I guess I should check the kill switch, key switch, and gear position sensor for starters.

Does the thumb kill switch type matter at all?
This one is different than older machines... it has a normally closed switch...
I remember that from shopping for tether kills.
 

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kill, dead , not alive.............

The kill switch is just an on or off switch........a break in continuity.............if this switch is bad in some way it could cause stalls or a missfiring engine at random. You could try disconnecting it when the engine is running to find out whether continuity is needed or not needed to keep the engine running. If you get a wiring diagram (schematic) for your machine you can trace each wire and know each switch's function along with knowing whether a specific wire is powered in normal operating or shut down. Then you can check each wire with a voltage meter back to ground (-). If you have power in a wire that should not have you are closer to finding the short..............But I'm leaning toward a partial short ....like two wires with bad insulation rubbing together at random.
I would suggest you getting a service manual for your machine. It will have schematic for the wiring and a lot of test procedures for different coponits.
Post a new thread for help in getting a service manual for your machine and some of these guys will kick in and get you connected with one...........They are a bunch of great guys for helping!
 

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Discussion Starter · #17 ·
I have the service manual on PDF.
 

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the tps on the raptor causes some issues. check the tps. off idle stalling and random stalling
 

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Discussion Starter · #20 ·
the tps on the raptor causes some issues. check the tps. off idle stalling and random stalling
Yep... and it's real real touchy on the KFX as well.
It checks out though.

But, it could still be a problem though I guess.
Dunno.
 
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