My Scura has acquired a cough - post TPS adjustment

[Pressureangle]

I recently discovered on mine, while replacing a cheap plug cap that broke, that the premium NGK cap on the other side had open circuited completely. Don't trust appearances. What gets measured gets done.

[PJPR01]

Spent a good hour with GStallons today, we made some good progress, and the bike will idle stably now, but anything beyond that and it's still not operating well.

After our session today, I did check the resistance on my original black plug wires and one is at 4.50 and one at 5.00.  They are only a couple of years old as well.  I also tried one of my new red NGK plug wires that I had made a while back, and both of those have similar resistance at 5.10, so as far as I can tell, with checking the wire resistance by themselves and also while hooked up to the coil (testing ground on the coil and positive end at the end of the plug wire), I'm not seeing any major discrepancy...

Now I'm wondering did one of my ignition coils possibly go bad...in all of this work with the TPS...seems unlikely but who knows at this point.

Spark plugs look good, still nice and brown, not sooty after letting it idle for about 1/2 hour today (with fan on!).

I may have to rip the tank off and methodically check for any blockage in tubing anywhere or anything may have become disconnected...frankly I'm just mystified how this TPS can cause such a change in running behavior, but I guess the bike is very sensitive.  Thankfully my CARC bikes don't have this setup...they're much easier to set electronically and balance the throttle bodies.

 

[docc]

Try checking your TPS mV (again) with the throttle plate zip-tied firmly closed (and all of the stop points relieved).

Still 157 mV?

Stays 157 mV once tightened down?

Remember, the TPS baseline indexes the Fuel/Ignition mapping. TPS out of spec = map out order = potentially dramatic (or annoying) changes in running behavior.

[PJPR01]

Thanks again Docc…Yup I did that again as well this morning before our session with GStallons and still sitting at 0.157 fully closed and all items disconnected, high idle screw loosened and not touching the idle cam, and 4.78 at WOT.  

 

[Pressureangle]

Frustrating. Nothing pops out at me. Can you go through the current symptoms, to clear the air as to status?

I'm leaning towards an electrical issue, whether ignition or fuel. I'd remake all the grounds, special care to ECU and any grounds on painted surfaces. 
Not impossible to have an unfortunate concurrent but unrelated issue, like a failing cam sensor.

[Randy]

Stumble after coming off of idle sounds like fuel issue.

[PJPR01]

Thanks Randy/Pressure,

I'm going to check again every electrical and fuel related connector as well after another conversation with Gstallons.  After taking off the tank, airbox this morning I did find that the thin rubber venting tube from the bottom of the gas tank was pinched in hard behind the starter, completely flattened, so will make a new one.

Will be taking out the fuel injectors and getting them cleaned/reconditioned as well as cleaning the throttle bodies until they are pristine with a new Colgate soft brush toothbrush and some cleaner.

Also have a new set of spark plug wires coming just in case.

Hopefully will make some progress in the next couple of weeks once the parts arrive.

Much appreciate all the ideas and help here from everyone and special thanks to Gstallons for spending time on the phone with me as well.

[gstallons]

IDK if it has ever been replaced but , it would be a good idea to install a new fuel filter and have that out of the way .

[PJPR01]

Thanks G…Yes the filter was replaced a few years ago…all flowing smoothly. 
I installed not long ago a new fuel downspout as well, new fuel sending unit, new valve gaskets after a valve adjustment, I mean everything was running great with no issues or leaks or coughs until I decided to mess with the TPS setting just to see if that would make it run even better.
 

It’s got a new TPS potentiometer now, soon new plug wires , and hopefully reconditioned injectors once I find a reliable place near by.   I wonder if somehow cleaning the housing of the TPS allowed some gunk to clog up something but I don’t see how as it looks like a closed unit.

Anyway…more patience…while I’ve got everything off I may install the clutch line extension described by Scud a while back as I have access to it easily enough now with tank and air box off.

fun fun fun!!!

[gstallons]

Most of this maintenance is done for idle and just off idle "cures" .Hopefully this will affect Paul's problem.

[LowRyter]

Just curious.  I wonder if there is a mark (or memory) of how far the TPS was moved during the reset and if it could be returned to the original position?   Is it possible to set the TPS by ear and to continually adjust it until the cough went away?  Perhaps it would be good to make a pen marker when adjusting.  

My bike has a low rpm power crater and occasional cough when I take off.  It was shown on a dyno.  I have to be careful sometime because it's right when I get my feet on the pegs and taking off.  I have to be vigilant on the throttle.   New plugs really help. 

[gstallons]

I think Paul's TPS is new , so you can't see where it WAS . I am not sure if this is a result or a symptom he was trying to cure.

 Do you know what your TPS v is @ idle now ?

[PJPR01]

This is one of those cases where I probably should have not touched the TPS since I didn't have any issues, no cough prior to deciding to check the TPS setting...it was the 1 step I had never done in the Tank Off Checklist...but unfortunately when I set it to the recommended 0.157 at full close, and buttoned everything up again, that's when my cough appeared for the first time.

Anyway, hopefully I'll be able to solve it with checking everything again.

Last night I checked again some items and I found an interesting item that may have been overlooked before and that was the left hand side spark plug wire wasn't entirely plugged in all of the way to the ignition coil, so I'm wondering if that will help once I get it all buttoned up again.

 

[gstallons]

It won't hurt to make sure it is buttoned up ! Make sure you check the continuity of the entire circuit , like we talked about , too . Measure the resistance of both sides to get a baseline for a proper value .

[PJPR01]

Update:  All fixed!  Finally had some time to get back to the project, have been busy at work and riding the Tour of Texas and other activities so the Scura was sitting waiting for attention.

Anyway, a few weeks ago at Gstallons recommendation I took my fuel injectors to get reconditioned...that was excellent advice and both were in need of it, but the left one in particular was quite under performing vs. the right one.  All of the other items, wires, coils all checked out nicely with no need to replace but I had bought spares anyway just in case.

At any rate, after all kinds of fun cleaning the throttle bodies once they were off, sorting out stripped screws on several of the mounting spots, putting in new hex head screws where appropriate, I got it all re-assembled, set the new TPS adjusted properly at 157 mv fully closed with throttle disconnected, high idle screw loose and idle screw backed out (TPS measures 4.78v at WOT w/o linkage connected) and the tuning began again.

What I found:  The air bleed screws needed to be set differently from left vs. right and in all of my previous attempts I had kept them identical as per all of the prior write ups.  Playing with each of the settings and watching the results on the Carbtune, despite cleaning the throttle bodies thoroughly and the bleed screws as well, there's some inherent mismatch on the throttle bodies, that with an extra 1.5 turns out on the RHS vs. LHS, they balance perfectly at idle without the throttle body linkage connected and it idles beautifully and no cough either.  I managed to set the idle screws at almost identical levels as well w/o the linkage connected using a feeler gauge technique Gstallons had recommended.  

Once the connecting rod was reconnected and dialed in until just one or two threads were showing from the locknut vs. the plastic cup, the bike maintained its balance at idle and was perfectly balanced also  at 3k RPM's on the Carbtune.

Well...off on a test run we go, around the block seems perfect, so let's go for a longer run.  A 100 miles later on a cold Houston day, and it's absolute perfection, beautifully smooth, not a single cough of any sort, and feels like much lower vibrations than before.  Dare I say it runs better than before...I believe so.  Will get some more runs on it over the next day and weeks and hopefully it stays as good as today.

Big thanks to all and especially Gstallons for the time we spent on the phone...hopefully it's set and I can rack up some more miles on it now!