wot misfire... help

[dago mooserider]

I'm lookin for some help figuring out my bad misfire problem. So it only does it when i've been riding for awhile and the motor is good and hot. This is the kicker.... as the speed and gears increase it gets better. So, first and second gear it completely falls on its face, third is better, fourth its not really noticeable and fifth it will wind out to 135+ mph. It idles fine and revs up good when u twist it sitting there. I've replaced the plugs, swapped out the icm and bypassed the bank angle sensor...no help.  I checked for vacuum leaks and cant find anything. Plug wire or coil(s)? Its a 98 but only has 30,000 on it Waddu guys think?
Thanks in advance...
Matt

[Ricky-D]

Please explain in greater detail what you mean by "misfire".

Can you describe what "completely falls on it's face" exactly indicates?

General terms are good but you've already gone  to some length to fix the problem

with no success so more description of the problem would help greatly for the

goal of correcting the ailment.

***

[Michvalk]

Sounds to me like your hitting the rev limiter in the lower gears

[art]

Carbs, I had the same around 80000 miles. I also did the fixes you did and finally changed the carbs instead of rebuilding. Only because I got a good deal on a good set but they may need cleaning and new jets. When the jets get clogged up this happens.

[dago mooserider]

The bike shudders, bucks and backfires a little to and barely accelerates. But only in the lower gears. Its like the timing is off or something. I unplugged the cylinder that i thought was the culprit and ran it on 5 and it still did it. So its multiple cylinders. I think its a spark problem and not the carbs but dont know for sure. Definitly not the rev limiter although it kinda does feel like it.

[dago mooserider]

Art, did u notice it being much worse when the bike was hot? Thats what really has me confused

[Patrick]

Seems like the classic plugged low jet problem. How does run at 1500-2500 rpm ? If it stumbles and just generally runs crappy [technical  term]  at those engine speeds but runs OK above 3K then thats your problem.
Its not a good idea to disconnect and run the engine for long on a waste spark system.
I'd first recommend getting rid of the old fuel, adding new non ethanol fuel with a HEAVY dose of fuel cleaner. Then go ride it at low engine speeds.
That is, unless I'm completely misunderstanding your post.

[R J]

Did you modify or change anything just before this happened?

Do you have a fuel filter on it, one you added or some one added?

Have you looked in the tank for rust?

The answers to the above must give us some idea as to what's wrong.

As a general practice if I add something to the bike and it starts running crappy a short time later, that is the 1st place I go.   I added a inline fuel filter once in Florida at Bike Week.    Put it in the 1st day there.    Took it out 3 days later.  It is somewhere on the beach behind the cabins we rented for the week.  I doubt if anyone would take the time to stop and pick it up.

So, please more information.   Thanks.     

[dago mooserider]

I haven't changed anything recently. The bike has never sat longer than 3 weeks. I had the carbs redone about 2 years ago at factory pro and im pretty sure they put in the larger pilots. I do think the problem has been progressive-getting worse the last few rides. I have done tankfuls of seafoam and didn't notice any difference. I will try it again tho...
The bike seems fine at low rpm and super high rpm its like the 3000 to 5500 range...

[R J]

I'd recheck those little vaccum lines for cracks.

You never said, do you have an external gas filter?

If so remove it for sheet & grins and see if your problem might just go away.

Secret to adding anything in the gas line, it has to flow DOWN hill.    Any rise in the flow will give you a lack of fuel, and it will pop, fart and snort back at ya.

[dago mooserider]

Now that im reading my own post, it is starting to sound like the stupid carbs. 6 carbs what a-hole at honda thought of that....    thanks for the replies guys...   no, no fuel filter. I've not touched it since the factory pro dudes jetted it

[gordonv]

You mentioned Seafoam added. In what amounts?

When adding as a fuel additive, follow can's instructions.

When adding as a solution to a problem, you want mega strength.

1/2 - 1 full can to a 1/2 - 1 full tank of gas. Mix with running time and sitting time, to allow the additive to do it's job. Also running the engine in the RPM range of the problem, should get the additive where you want it (usually low RPM, high gear/low speed on the flats).

It's doesn't matter how long ago you did clean the carbs, they can clog again, over a winters storage.

[R J]

Refer to Gordonv's post and when ya add Seafoam, like he said run it in the Rpm range you said you had the problem for a few miles.

Let it set overnight after running it.

Take it out the next day and run it again in the same RPM.

If it still needs to set overnight do so.

Next day or 2nd day take it out and run it like ya stole it.   If it still craps on ya, you are going to have to go deeper.

[Michvalk]

I wonder if it's possible to have a wire swinging under acceleration and shorting. Might explain missing under accel in the lower gears, but running fine in the higher gears. Just a thought

[R J]

I wonder if it's possible to have a wire swinging under acceleration and shorting. Might explain missing under accel in the lower gears, but running fine in the higher gears. Just a thought

Factory wiring is pretty well covered and contained.

If added wiring it is a possibility.

But, I think he said he hadn't made any changes to it.

[Patrick]

The problem being in the mid engine speed ranges bothers me, thats not normal for these monsters. I'm also thinking vacuum line breaks/cracks or even carburetor diaphragm cracks,etc.

[pancho]

 Hey dago,,,  from the information you have provided, I would be suspecting the fuel delivery system,, If you are sure there are no vacuum leaks, try the carb cleaner method several have recomended, if that does not fix it,, take the carbs apart and clean and inspect.

[Ricky-D]

I think of all the gasoline additives, when considering trying to correct a fuel system problem, Seafoam is the least effective.

There are others that are reported to be more effective to clear up carburetor related problems.

Techron is one that has received praise along with Berryman's B-12.

With any additive that's being used to cure a problem, massive doses is usually the norm.

And being in a hurry is definitely not the regimen. It takes time for these solutions to do their work.

***

[pancho]

Yeah, I should have included  a recommendation for a carb cleaner.. I use Berryman B12 as Ricky-D mentioned,, it works and it is cheap.     $3 at Walmart.

[lljjmm]

Process of elimination - take out the guessing and what ifs, 

First - change out you vacuum lines,  they may appear good, but does not mean they are (Talking from  experience). Not a hard job.

Then you can move on to other stuff such as the carb additives, drain tank to rid of possible water/crud in tank,  carb clean etc. 

[art]

Art, did u notice it being much worse when the bike was hot? Thats what really has me confused

It's been 6 or so years but it did get worse as I road around for a while.I wouldn't say hot but up to temp.

[art]

PS I have had two so called mc mechanics at a total cost of $1000 work on my valk and nothing was accomplished. I do my own work now. Thanks to some guys on this board like Patrick and Ricky-D I have done work on the carbs and replaced the head gaskets and did a valve job. Working on a valk engine is a piece of cake. As to the carbs, if taken care of they do not screw up and work well. Just don't let the valk sit ,It likes to be run at least once a week. I'm kind of worried about my valk because I cannot do anything to it since I had my accident a month ago. I will start it but I cannot even move it.

[dago mooserider]

Thanks for the suggestions guys. I'm gonna dose it with berrymans and see what happens. The problem seems so much like spark to me but if it is the carbs thats actually a good thing.....  my valk has a date with attic rat next month and he'll get these carbs sorted out. I just didn't want him chasing multiple problems.

[Rio Wil]

If I understand the symptoms, I find it hard to believe you have any kind of fuel delivery problem. If this bike runs from 0-135 mph without misfiring when cold (or not real hot), them you don't have a fuel delivery issue.  I would suspect a vacuum line that when hot sags and causes a misfire, perhaps a bad ignition coil or connection on a coil that heats up and becomes a resistive connection.......or maybe a pulse generator gap issue? When carbs are cold and run perfectly, they don't suddenly develop clogged jets when hot.......

 

[Hoser]

I have found that when riding around at low rpm with the preferred mix, close the choke frequently at higher rpm.  It seems to help the process.  Hoser 

[Patrick]

You don't happen to be using an aftermarket ICM are you ?  Other than that, it doesn't seem like an ignition issue.

[longtom]

My two cents would be to agree with Patrick on diaphrams ,maybe needles sticking. aside: curious how you bypassed tilt sensor ? Some of us studied schematics a few yrs ago and never did see hoe to do it.

[Robdawg13]

Thanks for the suggestions guys. I'm gonna dose it with berrymans and see what happens. The problem seems so much like spark to me but if it is the carbs thats actually a good thing.....  my valk has a date with attic rat next month and he'll get these carbs sorted out. I just didn't want him chasing multiple problems.

You're in good hands with Attic Rat - He'll get it sorted out.  He fixed problems with mine that I didn't even know I had...

[dago mooserider]

You don't happen to be using an aftermarket ICM are you ?  Other than that, it doesn't seem like an ignition issue.

No, its an interstate icm. I also tried the stock standard one with no change.

[98valk]

check petcock diaphragm for pin holes in the flexible coating, use magnified eye piece.
 do a search many threads

[dago mooserider]

My two cents would be to agree with Patrick on diaphrams ,maybe needles sticking. aside: curious how you bypassed tilt sensor ? Some of us studied schematics a few yrs ago and never did see hoe to do it.

I literally just hot wired it. The connector has three wires going to it, i forget which was which but i just alligator cliped two of them together-bypassing it. I keep a small piece of wire under the seat just in case it ever goes bad.

[indybobm]

My two cents would be to agree with Patrick on diaphrams ,maybe needles sticking. aside: curious how you bypassed tilt sensor ? Some of us studied schematics a few yrs ago and never did see hoe to do it.

After looking at the schematic, you would disconnect the 3P connector at the Bank Angle Sensor and jumper the Red/White Wire to the Green Wire.

There are two parts to the Bank Angle Sensor circuit. The first is the Bank Angle Sensor itself.  The second is the Bank Angle Sensor Relay.
The Bank Angle Sensor has an ‘internal’ relay which is not energized until the angle of the bike reaches a certain angle. This unenergized ‘internal’ relay supplies a ground to the Bank Angle Sensor Relay through its Normally Closed contacts.  The then energized Bank Angle Sensor Relay supplies 12 volts through the Engine Stop Switch and Starter Button to the Starter Relay.

When the angle of the bike exceeds the allowed angle, an internal contact in the Bank Angle Sensor,  (think of it as a pendulum swinging side to side) supplies a ground to the ‘internal’ relay in the Bank Angle Sensor, energizing the ‘internal’ relay which opens the Normally Closed contacts.
This removes the ground from the Bank Angle Sensor Relay which de-energizes that relay and removes the 12 volts to the Engine Stop Switch, the Starter Switch and the Starter Relay.

The ‘internal’ relay in the Bank Angle Sensor is a latching relay. It will remain energized until the ignition key is switched off.

[dago mooserider]

Well guys, y'all called it... full can of berrymans and rode around at all speeds and plenty wot. Its like jesus himself touched the bike, that stuff is a miracle. Seafoam didnt help btw. It still isn't 100% but after the way it was running i'll take 97% any day. I'll dose it again and see what happens. Thanks to all who replied

[pancho]

Good deal,,, really like those simple fixes.

[gordonv]

Nice to hear you are getting some where with this issue.

One thing no one mentioned, which you found out, it was posted a while ago (2-3 yrs) that any one type of cleaner did not work to fix the issue completely.

Seafoam fixed it X amount.
Berryman"s fixed it Y amount more.
Terchron fixed it up Z amount more.
Now can't notice the issue any longer.

One reason I now use Esso fuel, for the Techron. I don't ride daily, and figure for the same cost of other fuels, I get a little additive to keep my carbs clean, and the bike worry free.

[Hoser]

If it pukes on you at around 6000 rpm, you may be up against the rev limiter as previously   mentioned.  Try shifting at a lower rpm. You can also rev it to the redline in neutral, If it still has a rev limiter hooked up, it will puke.  If some one disabled the limiter in the past, you may hurt something, though.  Hoser