Stammering 2012 wr450

Bike runnin great, pulled into gas station, filled up.  1/4 mile away from the station the bike stammered when trying to accelerate. Similar to a rev limiter without redlining. It is a consistant symptom, not erratic or intermittent. Made it home 10 miles in this condition, uphills being the greatest challenge.  Checked the fuel. (no water). Fuel pressure, 50lbs. Injector, 4ohms. TPS sensor, 5k. Cleaned air filter.  Changed Sparkplug. Coil is good, checked Primary, Secondary, and the cap, all correct impedance. Checked mapping on ECU. Tried stock ECU. Charging system working. When I checked the timing, it looked like I was clockwise one tooth on both cams. the R side intake cam punchmark was below the head line, and the L side exhaust cam punchmark was above the head line. Adj the cams so they sat even with the head line and it ran worse. Put the cams back to the pictured orginal setting. Don't know what to do next. Krannie if you answer this I promise I will pay close attention. lol.

wr450 cams 023.JPG

Edited by comp123

Drain the fuel and replace with new from another station. It's the only thing that changed during your ride.

I checked the fuel in a clear jar and did not see any type of separation. I did not try different fuel. Will try fresh fuel tomorrow and let you know.

Have you been filtering your gas from day one? 

 

It sounds like under load the problem is worse?

 

I would bet its a dirty injector or damaged pump.....the pump pressure drops after about 2+ min if the pump is going bad....it takes a while for it to get warmed up.

 

 

A dirty injector is what I think the symptom is.....and if you have not been filtering your gas, I'd put money on it.

 

Pull the injector, pull the nozzle, and put a rubber hose on the end of it.

Holding it with the hose facing up, fill the hose with solvent.

Using a air compressor hose with a tapered tip, force the solvent through with air pressure, into a paper towel.

Repeat till the solvent coming out is clear.

 

If the injector is dirty, so is the fuel pump filter, so clean/replace it (can't remember is this pump has a detachable filter....)

I have not been filtering my gas. My WR is street legal so  normally its gas pump to tank.  It is definitely worse under load. Will put in fresh fuel tomorrow first and proceed from there. can't thank you guys enough. Let you know.

Drained all the fuel and replaced it with new. Took out the fuel injector applied 12v to open and pushed solvent through it at 50 psi. It looked clean. Started the bike, same problem. No change. When I put 12v to the injector at the bench, I can hear it click open. When I plug it into the bike I do not hear it click. The factory injector plug shows 12v with ignition on.

Must be electrical then

 

Check you stator pick up for debris, coil ground, harness ground, battery ground

You won't hear it click. The duty cycle is to fast to slam it wide open. Did you check your valves? Did you check the compression? Bad valve or broken spring. 

Edited by vlxjim

Have not checked the valves. Cannot do a compression test on this bike only a leak down.

Checked the stator coil as per the owners manuel. 1&2=1ohm. 1&3=1ohm. 2&3=1ohm. Yamaha wants to see an impedance between 0.582 and 0.792. Could this be it?  All my grounds are solid. Charging system OK.

Checked the stator coil as per the owners manuel. 1&2=1ohm. 1&3=1ohm. 2&3=1ohm. Yamaha wants to see an impedance between 0.582 and 0.792. Could this be it?  All my grounds are solid. Charging system OK.

 

Yes, but you need to make sure you have a meter that will resolverdown to .010 ohms or it will be meaningless. It will hunt for a measurement, and give you an average/RMS random number.

 

The typical multimeter won't do this.

 

You can make sure by measuring a known resistor that is .5 and another that is .1, to find out, or by just looking at ther meters specs.

 

 

Did you look at the stator pick up, for ferrous debris stuck to the magnet(s) or pickup?

Used a 4ohm speaker to verify my meter.  I have a good Fluke at work I can bring home to double check.  I have not opened the motor yet to look at the pick up. I will do that as well.

Thanks. Have to take wifey out now. Let you know.

Used a 4ohm speaker to verify my meter.  I have a good Fluke at work I can bring home to double check.  I have not opened the motor yet to look at the pick up. I will do that as well.

 

A 4 ohm speaker is not 4 ohms though.

 

That is a 'nominal impeadance' measurement, using a 1k test tone signal.  A 'typical 4' ohm speaker measures at about 3.4 - 3.6 ohms resistance.

 

You need to measure a known resistance at least half of the spec number for the stator, to know if the measuring device will resolve enough..........

You cannot do a compression test at all, because of the automatic release, correct?

 

I think you better get on that leak down test. This could be mechanical. Did I miss it, or did you fail to mention

 

in a previous post, that you previously ran it almost out of oil, prior to this? Running your engine

 

with a only a few ounces of oil in it will not be good for longevity, lol.

Edited by RRM707

If he had low compression, the motor would not idle.

His problem occurs only under load, and any leakage would occur at any rpm.

 

Compression test is about 65 with auto decomp and 135 with it bypassed.

 

It's NOT compression, if it idles!

It does idle. Just checked the stator with my Fluke and all is good. After I check the stator pick up I guess I should look for a bad valve or a broken spring. Heres a video of the bike running. http://www.youtube.com/watch?v=tN3awR0PBPw

Sure sound like a fuel problem. It still could be valve or spring problem. But I would still look at a fuel problem. Check the TPS, APS and the fuel pump again. If you have the Yamaha diagnostic tool you can look into this a lot better. The tool can start the fuel pump fire the injector read the output on the TPS and APS. If it was timing or weak coil one would expect misfires and backfires.  

Sounds like a good idea. I am not comfortable taking the head apart, when fuel can be the issue. I will look into testing my fuel system further than I have. There are still a few things I can try before I go to Yamaha or try to borrow a diagnostic tool. Thanks for your help, will keep you posted.

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