2012 WR450F Starting Problems




I have been reading things on this forum for quite some time when trying to trouble shoot but I am new to posting.


Anyway here is my issue, I have recently bought a secondhand 2012 WR450F and I am having some electrical troubles with it. it is standard except for the yoshi slip on muffler. I have contacted the dealer and they have claimed that there is no warranty so I would prefer to fix the problem myself.


It is an intermittent problem so its difficult to find the source but maybe someone can help. When it starts it will run fine, it does not cut out unexpectedly, it makes good power and all of the electronics work as normal. Sometimes though, when i turn the ignition on the fuel pump does not prime and the starter button will not work, that is, I push it and nothing happens, It does not even try to start. It will not start on the kick starter when this is happening either.... When things are working the bike is great to start, when it isn't it won't start at all, no matter what I try. Then, without doing anything that seems as though it would fix the problem, I will turn the ignition on again and the fuel pump will prime and the bike will start and run perfectly. It may start fine the next 5 or 10 times and then it will do it all over again. Currently the bike is dead and staying dead, luckily this happened at home right next to the work shop so at least I didn't have to push it too far.


The relay that the safety switches (neutral switch, clutch switch, kill switch and kick stand switch) are tied to is not operating when I turn the ignition on. I have checked the switches with a multimeter and cannot fault them for operation. Which makes me wonder what else is connected to the relay (#19 in the wiring diagram I think) and where else I need to focus some attention. I find it hard to trace out because everything goes into joint connectors and I lose it from there. I should mention that my experience at reading wiring diagrams is limited with these sort of bikes as I am used to much simpler motocross bikes.


I am suspect of the lean angle sensor because I know very little about how much control it has over the starting and running of the bike. Could this be the cause of my problem?


If anyone could help to shed some light on this issue I would be thrilled to bits.



Lean angle sensors are known to be bad

Pump wiring connections inside take are known to be sub standard

Stock ECU and map is too lean / go with the GYTR kit and tuner.

So, I think I'm reading you bought it in this condition, it came this way, for you.


I think I agree w/ Krannie about his recommendations (lean angle sensor, pump wiring).


I would add "keep it simple" for the causes:  A loose or defective connector or connection.  Start with the battery terminals, clean 'n tighten.


On to the connectors you can find, each one of them: Unplug, examine and re-plug.


You're looking for corrosion, or poor physical connection.

Wouldn't the check engine light flash if the lean angle sensor was bad?  Maybe the kill switch is stuck on?  I see you checked the kill switch, nevermind that.

Edited by cracker please

Thanks guys.


I am running the Aussie bush map in it. When I test rode it the motocross map was installed and that was too aggressive for me given that I am just trail riding it so I had it changed before I picked it up.


It is hard to say definitively if this fault was present when I bought it but given that I have only done a few rides on it and it has been having issues since not long after purchase I would say that it was already like it. All I have changed on the bike is added radiator guards, bark busters and a B&B bash plate so I don't think it is anything I have done.


I have been wanting to tidy up all of the wiring on it anyway so I guess now is a good time to do it. I will start with the fuel pump connector though I think. Hopefully it stays broken until I find the cause because it is a bit worrying leaving home on a bike that may or may not keep going.

That's weird.  I think the starter would still crank if the fuel pump connection was bad.

Sounds like a sticky autodecomp. This happens to me once in awhile and I just need to rotate the cams a skosh and the starter will turn the crank again. Sometimes I have to use the kick starter to rotate the cams. I don't know how or even if the decomp can be adjusted to get rid of the problem or not. Feel free to chime in and educate me.

Edited by cubera

Sounds like a sticky autodecomp.


That wouldn't keep the pump from priming when turning the ignition on, would it?

That wouldn't keep the pump from priming when turning the ignition on, would it?

Don't think it would. What happens to me is that the motor just won't crank. You can hear the starter try to crank it but it won't budge.

That happened to me on my first ride on the bike too. I thought it was seized. Turns out it was just locked at top dead centre, I put it in gear and pushed it backwards a little and then it was business as usual.

So, a bit of an update. I spent most of the weekend getting my kx250f back together and only spent a little bit of time looking at the wr. I pulled the fuel pump out and everything looks to be ok there as far as I can tell. I also tested the resistance on the fuel sender unit as per the manual. My resistance reading is out of spec at 2.5 ish k ohms (manual states 1.3 to 1.9). Two questions, do people think this could be the cause of my problems? And the manual states that if this is out of range the fuel pump needs to be replaced so do these come as a pair and can it be repaired rather than replaced? (I ran out of time so I haven't pulled it out of the tank yet).

I don't think that the fuel sender will stop the pump or the bike from working.

No, as it turns out, this is a typo in my genuine yamaha manual. My other manual says replace the fuel sender unit which makes a lot more sense to me as they are listed as separate parts in the parts book.


My approach now is to trace the wires on the safety switches through all of the connectors until they end up back at the ECU in the hope of finding a fault along the way. It started working again once I had rolled it up onto the work bench so it will be hard to know whether there is a fault that I haven't seen or whether I haven't found it yet. Here's hoping I find something to blame.


Does the diagnosis tool have the ability to read anything other than the fault codes that the ECU logs? I am thinking that if it can tell me switch positions and stuff it would be hugely helpful in fault finding.

Edited by motoben508

I own a diagnostic tool, but it did not come with a user's manual (looks like a after-market knock-off, I obtained from India).


So, short answer is: I dont know. I think it does, because I've inadvertantly toggled (something), and I noted a change on the the diag tool display.

I think it explains a little bit about the sensors and codes in the fuel injection part if the manual.  Looks like it can test lean angle sensor voltage,fuel system voltage, and the neutral switch and clutch switch.  Nothing about a kickstand switch in the USA manual, I don't think we get one.



So it sounds like the diagnostics won't tell me much about the switches that I can't find with a multi meter and a little more time? the out put from my Lean Angle Sensor seems fine but of course, being an intermittent problem, who really knows?


Does any one know what circuit tells the fuel pump to prime? Is it tied to the safety circuit relay in anyway? I am struggling to find anything in the wiring diagram that links the two together so i'm guessing this command would come from the ecu? ie, through the relay then into the ecu and then out to the fuel pump to tell it that its go time.


Any time the fuel pump doesn't go the safety relay coil doesn't pull in either so I am guessing that they are linked somewhere and that also explains why the starter motor makes no effort to start.


I have tested the headlight relay (same relay) in place of the safety relay to no avail.


i am sticking with the thought that it is starting circuit related as the bike has not failed and I can't fault it on performance when it is running. if this is terrible logic please tell me but it seems right to me

Again, keep this simple at the beginning.


From the top, look at each connector. pop it apart, and examine, and push back together.


From your description, you could be facing something as simple as a defective, intermittent, on/off switch, or intermittent connector in that circuit.


Not knowing what the previous owner has done during their ownership makes it tougher, working "behind" someone else. Do-able, but tougher. Start by believing they were not good at whatever they were doing to the electrical, and look for evidence of their having "touched" something.

I agree with mebgardner, keep it simple at first.

Your primary tool will be an ohmeter / voltmeter

The problem is intermittent, so take opportunity to diagnose when it will not start

....although it seems like you wont know when it is good again.

When it happens i'd pull it immediately in the garage and rip all the plastic off for access to everything


I'd first double check all of the 'nannies'....clutch swicth, lean angle, etc

All of the interlock switches that prevent it from starting

(I disabled all of mine....one more potential failure to leave you stranded)


What have you tested so far and 100% sure its OK?

I have tested everything that I can put a meter on. Diodes, connectors, switches. I have tried to see what will cause the fuel pump to stop. Turns out the safety relay does for those of you that were wondering. I can't get the bike to fault now but I have not found anything at all that makes me feel like I have fixed anything either.

There have been no loose or dirty connectors. No rubbed wires. Nothing squashed. Nothing suspect. I'm just going to have to ride it until it faults now.

Definitely taking the fun out of buying a new you but oh well.

So... After a lot of tinkering and finding nothing I decided that i didn't want to ride a bike that I didn't trust. I have traded the second hand one back to the dealer for a brand new 2014 model with some cash his way. I lost some of my money on the deal but at least I have a brand new bike that I can trust now and I won't ever be faced with the decision of losing a huge amount of money or selling a dodgey bike. Anyways, here it is.

ImageUploadedByThumper Talk1408364608.150834.jpgImageUploadedByThumper Talk1408364621.601233.jpg

Parts are as follows

Msc fold away mirrors

Ego bark busters (I don't like the ones in our off-road kit)

Force radiator guards

RHK bar risers

Yoshi muffler

Tail light from the off road kit

Brake snake from the off road kit

B&B bash plate

Still waiting on my LED indicators to arrive

It is running the competition ecu with the Aussie map in it and I am thrilled with it. I've got 2.1 hours on it at the moment and itching for more.

Edited by motoben508

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