08 xb12r Won't run, backfires through intake. Help please

[Frankxb]

My 08 xb12r will only start for a short time after numerous attempts then stalls. Any try to keep it running results in backfiring through the intake. Replaced plugs, IAC, checked maf sensor. Been using ECM Droid to move maps in and out. Maybe thinking it is a voltage issue or possibly a bad ground. At first it was random and corrected itself after warm up. Now a no start issue. Any ideas guys? Ill try checking the stators tomorrow.

[Cooter]

It's not the "stators"...
Now that you have messed with a bunch of stuff totally randomly, this will be harder than it need to be. You are all over the place, when the only way to find the problem is a systematic diagnosis.

In honor of Mr. Pirsigs recent passing, I shall paraphrase for you his quote from "Zen and the art of motorcycle maintenance" that should change your life for the better, but only if you allow it too.

'If the answer to your diagnostic question in indeterminate (mu), you must broaden the question.'




TPS re-set, and check for an intake leak, or a snorkel boot thats off the airbox base.

[njloco]

Listean, there should be a sticky stating that, if one has an issue or issues, one should not touch anything on the bike unless 100% sure of what is wrong ! You only make it harder for the guys here that truly want to help you.

Maybe it's because I'm old and have some patience now that I say this. When I had a problem with my Ully, I was able to figure out out on my own but, only because I read up here about the symptoms I was having and I was sure I new what to do first, I didn't have to buy anything to fix the bike, it was as simple as cleaning all the grounds !

Whatever, do what you must, hope you solve the problem.

[user_deleted]

My 08 xb12r will only start for a short time after numerous attempts then stalls. Any try to keep it running results in backfiring through the intake. Replaced plugs, IAC, checked maf sensor. Been using ECM Droid to move maps in and out. Maybe thinking it is a voltage issue or possibly a bad ground. At first it was random and corrected itself after warm up. Now a no start issue. Any ideas guys? Ill try checking the stators tomorrow.

1-your 2008 xb does NOT have a mass air flow sensor
2-your symptoms were NOT the result of a faulty IAC unit.
3-moving maps "in and out"? really? why?
4-" voltage issue" as you stated typically activates your CEL if even intermittently and sporadically.
5-back-firing thru the TB into the airbox assembly is ALWAYS ignition/combustion sealing related and always will be. your problem lies within either your wiring, your ecm or your ignition system components.

[BuellyBagger]

My 08 xb12r will only start for a short time after numerous attempts then stalls. Any try to keep it running results in backfiring through the intake. Replaced plugs, IAC, checked maf sensor. Been using ECM Droid to move maps in and out. Maybe thinking it is a voltage issue or possibly a bad ground. At first it was random and corrected itself after warm up. Now a no start issue. Any ideas guys? Ill try checking the stators tomorrow.

It's busted... I'll give ya $1500 cash for it.

[Frankxb]

Thanks guys. Hear is what i got so far. I am all over the place with my diagnostics.I dont have a maf sensor ( stand corrected, was incorrectly referring to the intake air temp) and my bike is a piece of junk and only worth $1800 dollars. lol This is what i have verified already. No problems with the coil,wires or plugs. Cleaned the two grounds, one under the seat and the other one on the steering column. Also no problems with the stator, IAC, IAC or Battery. Turning my attention to the fuel system. A weak fuel pump or faulty injector. Also need to test the o2 sensor still. I have a fuel pressure tester but having problems finding the right adapter. Any one know where this adapter could be obtained? The kit from harbor freight does not contain the right fitting.

[34nineteen]

My head hurts just reading the symptoms.

First it doesn't run.... wait.... it does run, but stalls. But its not stalling, because you can keep it running, but it backfires. But, the bike doesnt start?

Here is a great video pointing out a proper diagnosis technique, and has been proven over the years. I'm very surprised lunaticfringe hasn't pointed this out.

https://www.youtube.com/watch?v=AynXoLjYrKc

[lowkey]

This is what i have verified already. No problems with the coil,wires or plugs. Cleaned the two grounds, one under the seat and the other one on the steering column. Also no problems with the stator, IAC, IAC or Battery. Turning my attention to the fuel system. A weak fuel pump or faulty injector. Also need to test the o2 sensor still. I have a fuel pressure tester but having problems finding the right adapter. Any one know where this adapter could be obtained? The kit from harbor freight does not contain the right fitting.

What led up to this issue? Was the bike parked for a while? Or this happened suddenly after riding it right before (within days)? Was it fine then all of a sudden or was it sluggish/random backfire/engine light coming on leading up to where you are now? Did you work on ANYTHING then this happened?
Getting the plug wires seated can be tricky so make absolutely sure they are seated on the plugs, when done right you will feel and probably hear them "click" into place. As lunatic pointed out with a backfire through the intake you are looking at improper spark/timing or leaking intake manifold gaskets.

Here is the resistance tests for coil/wires from the service book:

coil - 1) primary resistance - Normal resistance range is 0.5-0.7 ohms. (tested on the 2 outer terminals where harness plugs into coil)
2) secondary resistance - Normal resistance range is 5.5-7.5K ohms. (tested at coil wire front/rear leads)

Test Results
1. A low resistance value indicates a short in the coil winding.
Replace coil.
2. A high resistance value might indicate that there is some
corrosion/oxidation of the coil terminals. Clean the terminals
and repeat resistance test. If resistance is still high
after cleaning terminals, replace coil.
3. An infinite ohms (∞ or no continuity) resistance value
indicates an open circuit (a break in the coil winding).
Replace coil.

wires - Spark Plug Cables SPECIFICATION FRONT & REAR Resistance -ohms 1,430-3,360

If those check out as you have stated, you need to test/inspect/replace your intake seals. I know it is impossible to do by the book when you can't even get the bike to run to perform the test but This is where you need to put your focus before moving on to anything else. If you can have a second person give a hand you can control throttle to keep the bike running while they fish a propane hose around the seals from either side of the bike with the scoops off. If it was me, I would just replace them as your next move, they are always in various states of needing replacement so if you don't know their condition you will after you do them. I used a snake camera through the TB to inspect them after I put the new ones in to make sure they were seated properly, they can very easily shift and get pinched while sliding the manifold into place.

As for finding a fuel pressure testing kit with the right ends... good luck! I just went through the same situation, everyone likes to through out to test it but offer no insight on where they are getting a compatible pressure kit from... I'd wager few if none at all have actually performed this. In the end I had to cut the factory fuel line and use the brass connection at the pump to rig up to. I hose clamped fuel line to it then to the gauge. You should see 51PSI key-on pump priming then a steady hold of pressure at 49PSI. Remember this isn't the whole story for fuel as you now will need to test flow as well. For this I used a stop watch app on my phone, with two pump primes using the switch at the right hand control and the rigged up line off the pump into a measuring cup, my results were as follows:

2.4 oz @ 5 seconds (2 pump primes = 5 seconds)

28.8 oz @ 60 seconds

1728 oz @ 1 hr = 13.5 gallons an hour

[34nineteen]

Start with the basics:

All engines require 3 things to run: fuel, ignition and compression.

Lets focus on fuel first....


Pull the airbox cover and see if you can get it to run on ether. Make sure its ether (aka starting fluid) or FLAMMABLE carb cleaner. This guarantees you have a flammable "clean" fuel source. If you try to save $5 and just use the gas in the tank, you are defeating the purpose of this. Who knows, maybe the PO had somehow got a bunch of water into the tank? I've seen some weird ****.

If the starter is turning over the motor, spray a blast of ether down the throttle body (with the throttle open) and see if it will start. If it fires up, even momentarily, that points to a fuel issue.

If you're spraying ether into the intake and its not running, you do not have a fuel problem. Bear in mind that ether is very flammable and can catch fire or worse. Be careful.

An engine does not *require* "47psi" or a specific "gph" to *run*. Right now, getting it running and keeping it running it your #1 concern. Note: running does not mean "driveable". "Driveable" is another concern further on down the path of diagnosis.

[lowkey]

34nineteen, he should be looking at the intake seals before worrying about fuel, I posted specs per the manual and my own findings because he was focused on fuel, I have no idea if he has a manual or not so there it is in one post. His wording leaves much to be desired on the running condition but I know what he is dealing with as my bike was acting the same so I "read between the lines".

OP the quick and dirty way to take your mind off of fuel for the time being would be to disconnect the fuel line from the rail and feed it into a bottle, flip the switch on for a pump prime, see flow? Connect the line back up and start focusing on the intake seals.

Do not feed fuel into the TB, only propane/brake clean/carb spray around the seals/flanges on the outside of the manifold, you will see a change in the running condition if only for a couple seconds with this method, works well and you can even pinpoint which cylinder is leaking with this method.

Twinmotorcycles intake seal test:
https://www.youtube.com/watch?v=5MvohPCZazY

EDIT:

OP you could very well have water in the fuel, did you fill up before these issues or run the tank down/dry. Using the above "quick and dirty" fuel flow test above you can see if there is water in the fuel. This method is also the cleanest best way to drain your tank if you end up needing to pull the pump for some reason.

If you have any tuning software available to connect with the bike, you can always use the "injector test" and with a snake camera to view them to rule them out. You can choose which injector to fire and they will spray 3 or 5 times in a row (can't remember). You also mentioned you were worried about the O2, if it was then it will be stored in the ECU as a fault. Keep in mind an O2 needs to come up to temp before the data can be used by the ECU so there should be about 45 seconds to a little more than a min where that data isn't being referenced at all on a cold engine.