XB9 - Rotated Engine Now Doesn't Idle/Run??

[brandn3w]

RESOLUTION

Owner/Mechanic (me) is terrible!! Rear cylinder intake pushrod wasn’t fully seated on the lifter causing HUGE gap and not allowing rear cylinder to even fire/run. Thank God - easy to just seat appropriately and put back together

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Quick overview: Had a rear rocker gasket leak so rotated the engine down following the DIY tutorial here (extremely grateful) and replaced the lower and upper cover gaskets and PVC grommets and hoses while also painting the rocker covers. Once back together, started and idle surged mildly and ran super rich unable to give it throttle without killing it and backfiring thru the intake.

So this is what I've done so far:

• Metered Spark Plug Wires and got >2000ohms so they're good
• Metered Primary Coil terminals and got 2.5ohms on a 200ohm setting - is this my issue??
• Metered Secondary Coil and got 5.99 and 6.01 ohms on 20000ohm setting so they're good
• Metered TPS, but unsure what resistance it should have - any idea?
• TPS Reset using ECMSpy and verified original settings as well
• Checked system spark with ECMSpy and heard front and rear spark - could be weak even if it did 'spark' I'm thinking
• Spark plugs are newer (<500mi) and DCPRE9IEX, but ended up being fouled
• Replaced with DCPR8E
• Cleaned Coil Pack grounds, bolts, and base with sand paper, wire wheel, and CRC electronics cleaner
• Clean tie bar brace and all washer and contact points with sand paper, wire wheel, and CRC electronics cleaner
• Created extra ground from coil to tie bar brace to negative terminal to eliminate poor ground as a cause - did make it start easier and lights much brighter as well as metered 20% reduction in resistance

So at this point I'm thinking the coil is bad, but how odd that I rotate the engine then it's bad all of a sudden? I'm trying to think what I may have missed or disturbed in re-assembly so my initial thought from removing the TPS could have been the issue, but it was not. I also have a screenshot of ECMSpy logging live data as well to help with diagnosis. I took a log as well, but think the picture is much easier to read.

Below is the image and this is what I noticed that seemed odd:

• Spark Advance bounced from 0 to 20 the whole time
• Warmup Fuel is 117%
• Pulsewidth bounced around a lot
• Idle surged 1050 - 1350
• Region was cycling between "Idle" "Open" and "Deceleration"

In any event - with this information and what I've done so far what would be the next step for me to try? OR I can't get 0.5 - 0.7ohms on my DMM for the primary coil at the 200ohm setting, is my inexpensive DMM just not effective or is that my issue? Secondary measured out correctly at 6K (between 5.5K - 7.5K per the manual).

This site is great - I've learned so much and have done a lot with all the information here, but now I'm stuck and need some help so I'd appreciate any thoughts in advance. Thanks!!

[Cooter]

Thanks for the clear information for your diagnostic path. Seems like you have checked everything in the secondary ignition side thoroughly. What made you think spark is the issue?

Step back and look at the whole thing. Do you have gas in it? Is it completely re-assembled (because they hate to run with the airbox off)? What would you look at if you hadn't just rotated the engine?

and absolutely re-check all connections and grounds post engine rotate. I know, I know.. you've 'already done that', but please, step-by-step, take the time to unplug and plug all of them, look for pinched wires and hoses.

And check for an intake leak.

Because, like you, we're all just guessing.

[brandn3w]

Thanks for the quick reply!

I thought spark because the backfire through the intake + black exhaust + fouled plugs. It's getting fuel so it must be spark was my assumption since it takes fuel, air, and spark.

The bike is 100% back together with the air filter in and air box on and together as I thought running without that on may have been contributing, but after putting it all back together it was the same.

It has gas and it's not old gas as I refilled the tank prior to parking it to rotate the engine. I did have this issue years ago though when I thought my KZ440 bobber wouldn't run when it turned out to be empty - took a month to figure that out actually so you're definitely right to question it!

I'm going to look back through the tutorial and go back over the bike and make sure it's all together step-by-step to retrace my path. I've unplugged/re-plugged O2, ignition, coil, IAT, and TPS several times so they should be good and I don't have a CEL either so not sure it's a sensor.

Also - if I subtract my DMM resistance against itself from my reading on the primary coil then the coil tests out within spec as well so it (per the multimeter) is good.

Aside from trying to get it to run and spraying brake cleaner around the intake seals - is there any other way to check? I thought intake seal leaks caused lean conditions?

What hoses should I check? I can't think of any hose other than PVC, tank breather, and the hose that zip ties to the rear shock? Just trying to think...

[Barrett]

Sir: these are the "idle value" or "cells" for the pre-2008 XB12...but should be very close to yours. i would check to be sure they haven't been fiddled with.
i have seen the identical situation to yours 4X now...following an engine rotation, and reinstallation.
every single time it was a failed TPS unit. the conditions: back-firing thru airbox assembly...extremely rich sooty exhaust...fouled spark plugs...aroma of raw fuel from exhaust....refusal to idle....shut-down after 10 seconds or so of throttle input.
CHECK: wiring harness to rear cylinder injector and wire to O2 sensor. both known to chafe and wear thru from rubbing against components atop the motor.



TPS/RPM 0 800 1000 1350
12 100 110 110 125
8 100 100 94 79
6 80 75 68 54
4 75 67 52 47

[Cooter]

What year is your bike? If it's DDFI-2 ('03-'07), make sure the TPS re-set procedure was done including the idle screw and not just pressing the re-set button. The degree looks to be ok, but the throttle blade must match (unless DDFI-3).

Is the fuel feed hose from the pump to the TB ok? Did you take out that protective rag you put in the intake? I've done that... Is the airhorn boot on right? The base flange splits between the floor of the airbox, and there should not be any gap on the inside of the TB at all.

The coil is probably ok. Even if one half of the coil is completely bad, it can idle fairly well. It can even haul you all the way to Bakersfield at freeways speeds on one cylinder (Shut UP Aaron!!)

Spark timing could be an issue. Check the signal from the CPS (Cam sensor or Crank sensor depending on year). Also, a simple cheat is to use a grounded test light next to the spark plug wire (do NOT pierce the wire!!) let the magic of induction work and you can see the test light pulse when it sparks. Is it sporadic? Cutting on and off?

[34nineteen]

Did you put the injector plugs on the correct injectors? There is a separate front and rear plug. If not, they are firing at the wrong time.

[brandn3w]

Thanks so much for the answers!! Just went through the bike again carefully with my treble/bounce light while re-reading the engine rotation step-by-step and everything is in order.

Barrett —>

Those symptoms are EXACTLY what I’m experiencing - 100% on the money! But I metered the TPS and it reacts to throttle input and when using ECMSpy it goes from 5.3 degrees to WOT at 85 degrees. Is there another way to use the multimeter and check for it being faulty? TPS was one of my first thoughts since I had to move/remove it and it has the potential to cause these issues, but my meter shows it reacts to turning so it seems ok? Is there a way to check without just buying a new one?

The wires are all intact and they have some wear to their casing, but nothing worn through or exposed wire.

I don’t think anyone touched the fuel mapping as the bike ran great prior to the engine rotation/gasket change. The ECMSpy was just bought 1 week ago to do the TPS Reset and read live values to help with diagnosis.

Cooter —>

Sorry - it’s a 2007 so I needed the cable and ECMSpy to complete the TPS reset and it couldn’t get voltage to 0.0V but definitely got the plate to 0 degrees and adjusted up from there. I did add some fuel line as a shield around the the idle adjustment cable as heat has exposed the metal, but I just took it off “just in case” that was my issue.

Fuel line is all good and no rag in the velocity stack. Also went all around the velocity stack to verify no cracks or gaps and it’s all set plus whenever I put the air box base on I make sure to seal it around the base - good call out though as I did miss this the first time. I will admit I had to put some really strong downward pressure on it to get it far enough down to seal on the TB so could the intake seals be bad as a result of the force used?

I did not know that about the resiliency of the coil! It metered well and that information makes me stray away from it being the cause - thanks for that.

It’s a 2007 so I’ll have to pull my manual out to see if I have a Crank or Cam PS and I’m not sure I have used a grounded test light so I may have to read up on that process. I do have ECMSpy so I know I can test each coil so if I test it and I can hear/see it spark - would that be sufficient enough to confirm it is getting appropriate spark?

[brandn3w]

34nineteen

Cool build you have going on in your thread!

I was really hoping this was my issue and I keep looking for a reason that they’re switched, but it’s white to the front cylinder and green to the rear cylinder. Please tell me I’m wrong lol I’ve taken pictures before disassembly and Googled images and looked in the shop manual hoping that’s my issue.

[brandn3w]

So I just metered the TPS again and got really high resistance:

Common to Constant Power was 4130ohms
Common to Signal (rest) was 720ohms
Common to Signal (WOT) was 3860ohms

Does this sound right?

Also tried to meter the harness side with ignition and rub switch ON and couldn't get any reading at all. Makes no sense because CEL was on with it unplugged (correct) then plugged back in CEL was off so it must be getting power to it, right?

[34nineteen]

What about this?

Created extra ground from coil to tie bar brace to negative terminal to eliminate poor ground as a cause - did make it start easier and lights much brighter as well as metered 20% reduction in resistance.

Get a battery jumper cable and connect from the negative battery terminal to the motor directly. It seems your bike ran fine before this extra ground wire mod (which I don’t disagree with), so I would investigate this more closely-er. You may still have a compromised ground circuit.

Normally, a user named “lunatic fringe” will offer up a solution, but last I heard he was hunting great white sharks with his bare hands while free diving in the Atlantic. Absolutely legendary.