Low compression after 25.000 miles

[sancheezy]

No error codes At this time.

[stuna]

02 senor is fuel control
a slow sensor may not trow a code .

[skipperT]

The other thing I forgot to mention was the O2 sensor was operating (I put sensor back on the bike and watched the voltage changes as it was performing ) 0.9 volts which is a rich condition at the 02 sensor.  Thus the ECM should be adjusting to bring this down to 0.5 volt range.  But I wasn't seeing that adjustment.  I may need to to a better job of letting engine warm up and get to operating temp. 
 
This not being adjusted goes hand in hand as why I have low compression reading due to carbon buildup.  Something is not working right and I can't figure it out.  I may try disconnecting engine evaporate system and then watch voltage level from O2 sensor to see if this changes (while engine is running).

 
If you are using a regular VOM, you probably can’t tell if it’s good or bad. The voltage fluctuates too quickly for most VOM’s to register the change. The VOM averages it out - which is why you are only seeing 0.9 volts.
 
Remember how the o2 operates when in closed loop mode. It’s trying to get to 0.45v (stoich) by varying the mixture. So seeing values rapidly fluctuating between 0-1v is typical as the ecm changes the fuel injector duration.
 
You need a scope to test it properly.
 
I will do some research and see if there’s another way to test it without a scope.
 
-Skip

[sancheezy]

When I had it on the bike and blipped the throttle the volts would drop down to .65, but then instanously climb to .9 and stay there.  also when I had 02 sensor off the bike and put heat to it (once I was above 600 F).  It was very quick to react and move around.  I am thinking 02 sensor is reacting properly (still might be lazy).  But I am stumped why .9 volts.  I realize it fluctuates fast but I figure it would read .45 since it passes that twice as it cycles?  I will try and get vidoe and pictures when I remove tank for testing next time.

[sancheezy]

Here is the link on YouTube for vidoe of my O2 sensor voltage.  Notice the voltage stays at 0.94 at idle and drops upon twisting throttle. I am not sure this should function that way.  I am thinking this should be at 0.45 volts and then fluctuate as the throttle is blipped.  This maybe like others mentioned that the voltage meter measures the peaks of the volt readings.
 

 
 
 

[pattonme]

you're wasting your time using a cheap-ass meter. Get a scope.

[skipperT]

Here is the link on YouTube for vidoe of my O2 sensor voltage.  Notice the voltage stays at 0.94 at idle and drops upon twisting throttle. I am not sure this should function that way.  I am thinking this should be at 0.45 volts and then fluctuate as the throttle is blipped.  This maybe like others mentioned that the voltage meter measures the peaks of the volt readings. 

 
 

 
Ok, let’s clear up a couple more things about the 02 sensor on our bikes:
 
First, it’s only there for catalytic converter efficiency. Yes it does this by varying fuel injector duration but ultimately it’s about keeping the converter temperature in the sweet spot for cleaner emissions.
 
Second, the Ecm “reads” the voltage fluctuation at least 8-9 times per second.
 
Your multimeter can’t keep up with that pace. It “averages” the readings. Your VOM settings also determine if it averages 0.9v or 0.1 volts. You will NOT see the meter following the voltage changes because it happens too quickly. Hence, the (excellent) suggestion for a scope. You will also probably NEVER see a reading of 0.45v in real life because the ecm is constantly adjusting the FI duration to hit that number, which is theoretically stoich.
 
However, most good scopes cost thousands of dollars and we are talking about a $100 02 sensor here ( I used the number for discussion, I don’t know what they cost ).
 
Third, the ECM doesn’t even use the o2 readings until the coolant temp is at least 141 degrees AND the throttle position meets the parameters specified by the Yamaha programming engineers. Sometimes the throttle must be closed, traveling at a certain speed, gear position, slight acceleration vs fast acceleration, you get the idea.
 
I don’t know under what condition you made the video, ie was the bike up to operating temperature? The only way to validate what you’re showing above is to do the same tests on another FJ and compare the data.
 
I appreciate all the testing you are doing, but take it with a grain of salt. I’m sorry to have to say this, but I don’t think you’ll find anything wrong here. The data you are pointing out isn’t conclusive.
 
If you’re worried about the 02 sensor, replace it and stop worrying about it.
 
Run the ring free for several tanks, see how the bike runs, and then recheck your fuel mileage once it warms up and you have access to summer fuel again before assuming something is wrong. Especially if there aren’t any trouble codes.
 
My .02 cents and ymmv.
 
-Skip

[sancheezy]

I understand what your saying about the rapid adjustments the 02 sensor is making and how the voltmeter won't pickup on this.
 
It is my goal to find another bike and test that bike under the same conditions to have a reference as you mentioned.
 
The 02 sensor is not cheap.  $200 new.
 
 

[pattonme]

look carefully at the sensor and with any luck it'll be labeled with an industry standard part number. eg. Nippon Denso xxxx and you can buy it from an auto-parts store for a fraction of the price Yam wants for the same thing.

[sancheezy]

It says on sensor
 
59C-8592A
DENSO
149100-2390
10R17
 
But I can't find a cross this O2 sensor anywhere.  I am not having luck finding another bike that I can run a test.
 
This is what my O2 sensor looks like after being cleaned then ran for 800 miles.
 
 

[pattonme]

I ordered the Denso O2 sensor catalog. In the mean time can you measure the thread diameter and pitch, length under nut (to senosr tip) and how many wires are attached? Auto sensors are $10-30 and I'm sure this unit is nothing special. Also can you look at the bike wiring diagram and determine if it's a 'heated' plug or not?
 
Oh and length of the cable. with and without including the metal boot.

[norcal616]

4 wires
8.5 in long cable
18mm thread size
 
*** side note...last summer for 2 tanks of gas I noticed the FJ-09 idles at 13.9-14.1 AFR... cruises around 13.4-13.9 AFR and around 12.7-13.1 when accel hard... in general the FJ-09 runs on the richer end of the scale even with a tune that puts down power...
 

 
 
 

 

[sancheezy]

I ordered a bosh replacement:
 
https://www.magnumtuning.com/en/detail/motorcycle-bosch-o2-oxygen-sensor-universal-wiring/Yamaha/mt-09
 
It is a lambda sensor simular to the stock DENSO (4 wire) for $60.  Hopefully this fixes the problem.  I will have to use existing plug.

[Guest]

I have a 2015 FJ09 with approximately 24,000 miles,  At 23,000 miles I had a drop in gas mileage (went from 49 mpg to 42 mpg).  I decided that it was time for a set of plugs, valve adjustment, air filter cleaning, and new oil (I change every 2,000 miles).  I cleaned filter and noticed excessive moisture.  I  went ahead and cleaned-up filter excess moisture.  Yamaha dealer went ahead and adjusted valves and put new plugs in ($800 later).  They also ended up replacing cam chain tensioner since it started making noise after the valve adjustment.  When I got the bike back I noticed that the mpg didn't improve (remained at 42 mpg).  I also noticed that the bike was beginning to let out white smoke upon start-up that would eventually quite after a minute or two.  I also noticed that the white smoke had a blue hue to it (signs of burning oil). I decided that something wasn't right!  The white/blue smoke along with the drop in fuel mileage, along with moisture should needs to be addressed. 
I took the bike back to Yamaha dealer and asked them to access what the problem might be? They started the bike up and then recommended I take just take home and keep riding it as is.  I told them that the issues needed to fixed since I have a 4 year Yamaha yes warranty.  Thus they called yamaha up and asked what needed to done.  Yamaha recommended a leak-down/compression test determine what may be wrong.  Dealership and Yamaha corporate told me that I was responsible for the cost ($250) of test if nothing was found.  I agreed.  The test showed 165-170 psi in all cylinders (dealership tech said this is outside recommeded operating pressures and should be covered under the warranty).   Dealership submitted paper work to complete ring replacement to Yamaha corporate.  Yamaha corporate denied approval since they haven't identified any manufacturers defects.
 
At this point I am pretty upset because I have a bike that I paid over $10,000 for.  I changed the oil every 2,000 miles, cleaned the filter ever 6,000 to 7,000 miles, had dealership do throttle body synch and valve adjustment per the manual and they pay for any repairs to correct low compression until a manufacturers defect is found.  My rocommendation to any readers of this post is to not buy the Yamaha extended warranty.  Unfortunately any repairs that are not part of a hard and fast recall will end being paid for by the owner.
 
Unfortunately, Yamaha is recommending a further tear down of the engine seeking to find what the problem is (dealership wants another $500 for further tear down which I have to pay if nothing is found).  I don't understand why Yamaha won't own up to the possibility of bad rings and make right with a product they want to continue to sell.
 
At this point I don't recommend this motor for longevity.  I have since learned that in order to replace the piston rings you have to split the engine in half.  The cylinders are part of the engine case (top part of the block has to be pulled).  I would also recommend that for those who own this bike with any smoking issues to do a compression test.  I was supprised at how decent the bike ran at an under spec compression.  Good Luck.  My hope is that Yamaha stands behind their product for others that are in my position.
 
 
 

 
 
CLEAR case where you babied your bike to death. I know several people with 70k miles on an FZ/FJ-09 that wheelie Main Street on the regular. I've ran mine long and hard, use European spec Mobil 1 5w30 synthetic and haven't looked at my k&n air filter in 20k miles. 47mpg at a steady 90mph and not a puff of smoke... this engine just keeps begging for more!

[britelitebob]

So much for extended warranties, never bought one and never will, on anything. 
I don't track my gas mileage either, it's only peanuts in the big picture so why bother.