Runs great one day, horrible another! Any ideas?

[2002_wrx]

Hey guys,
    Just bringing the Vision back out of hibernation.  Before I put it away, I had cleaned the carbs, rebuilt the petcock, and fixed all minor leaks with new hoses, etc.  However, I'm having a bit of trouble getting it to run consistently.  It will always start without a hitch, idle on its own, etc.  But....some days it will run perfect, others it won't be rideable.  The symptom I notice most frequently when running poor is that the bike will still rev, but struggle getting up to higher rpms.  (past 5-6k)  I can't really find any changing variables other than the weather.  It seems to run better on warmer days, but today it was warm and it ran like crap.   ???

Any ideas what I should try?  Is this a symptom of poor carb tuning?  (Highly likely since I haven't really done anything tuning-wise since rebuilding the carbs.)

Thanks for your help

[YellowJacket!]

Probably still may be dirty carbs.  Water in the fuel?  How about the YICS?  Are the YICS hoses clamped or is it still being used?  Possible that it may be leaking which will cause lots of problems.

David

[Rikugun]

Is this a symptom of poor carb tuning?

From your description it could be any number of things but seems unlikely to be poor tuning since it's intermittent. Poor tuning would be all the time.

In addition to YellowJacket's suggestions, you might consider the rev limiter. They apparently can fail and may explain your symptoms. Some people simply cut the yellow/black wire (and tape the ends) at the 6 wire TCI plug. Or, you can remove that one terminal from the plug and see if the symptoms go away. If not, you can reinstall the wire to keep the rev limiter functional and search for your problem elsewhere.

[2002_wrx]

I wouldn't think the carbs are still dirty as I cleaned them out 3 times!  They are practically spotless and as clean as I think they are going to get.  I don't think there is any water in the fuel...I cleaned out the tank before filling it up with fresh fuel and the bikes been under a cover since.  The YICS is still being used...however when spraying starting fluid around the tubes nothing happens and I have leak tested the actual YICS box think.  That would be a good thing to double check though.

Rikugun:  I'll check out that rev limiter and see what happens when unplugged.  I wonder if that could be the case...it's not like the rev is cut off at a certain RPM, it just has a hard time revving up quick like it's supposed to.  I'll def give it a try though.  Any chance you could describe a little more detailed what it is I'm looking for?  I'm sure I've seen it, I just haven't put names to everything on the bike yet. 

I appreciate the help guys.

[Hartless]

the tci is going to be the black box next to the coolant bottle with wires going to it.its on the right side behind the side plastic.

[Rikugun]

Here's a great resource page 
http://www.jetav8r.com/Vision/IgnitionFAQ.html

Everything you ever wanted to know about ignition systems. Section 6 covers the rev limiter.

[PeteXS/GS/CB/XZ]

From all that you say, I suspect the rev limiter wire too.  (Mine is still intact and the bike runs fine.) 

[2002_wrx]

Well today I removed the rev limiter wire from the terminal, and it's been running great!  Let's hope it stays that way...I'm going to go start it up a couple times a day to see if it does.  Thanks guys...hopefully that was it!

[2002_wrx]

Well guys, I'm afraid I have bad news.  Apparently it wasn't the rev limiter.  It's running like crap again today.  Must have just been coincidence that it started running well when I removed the wire. 

What to do now...?

I really can't figure this out...it starts up and idles fine every time and the problem is so intermittent that I can't think of anything that would be causing it.

[Night Vision]

check your sidestand switch

[2002_wrx]

alright I'll check it out tomorrow.  I don't think that would affect it though since most of the time I've been trying to get it to run right, it's been up on the center stand.

[QBS]

Side stand switch (sss) failure is manifested by erratic and intermittent ignition cut off.  There is no pattern to the failure mode.  In my worst case experience of it (and there have been many) I was half way around an 18 wheeler on a two lane when the engine just cut out as if I had turned the key.  I had to back off behind the truck with no power and keep from getting hit by an oncoming car.  Bottom line: neither spark plug fires when the sss is in failure mode.

From the operational description that you provided at the beginning of this thread, your problem does not sound like sss failure.

[Re-Vision]

Side stand switch applies a ground when up, dirty contacts might possibly cause a problem like yours.    BDC

[2002_wrx]

Interesting...good to know.  I'll check that out as soon as I get a chance.

[kev10104]

Something simple like changing the plugs might help.

[fret not]

Check for leaks around any vacuum hoses and intake boots.

Maybe the fuel pump?

Also check any and all electrical connections, you may notice something while doing this arduous and intimate task.  One area to check for sure is the handlebar switches.  They get a bit of vibration and some weather, and I have seen kill switches fail on other bikes.  It can't hurt to have clean electrical contacts.

[mshowe]

I am sure you've checked this, but no one else has mentioned it.  Check all of the connections from the rectifier, stator, and tci box (and between all of them).

I am not sure what your 5-6k rpm is looking like, but the first time I had intermittent performance it was electrical.

Just a thought. 

[Rikugun]

symptom I notice most frequently when running poor is that the bike will still rev, but struggle getting up to higher rpms.

When the side stand switch fails it kills both cylinders so I eliminated that as a possibility. The rev limiter kills one cylinder and seemed more likely but is apparently not it.

Being intermittent makes it tough to diagnose - could be a million things but likely to be the last you check.. I usually think electrical with intermittent problems, but no guarantee of course. I'd start with the simple stuff like connections esp. TCI, coils, ignition switch & right handlebar switch.  Is the battery at least 12.5 and 13+ when running? Good luck!

[Tiger]

 :) If you have a spare one, change out the T C I....... ;)

                   8) ....... TIGER ....... 8)

[YellowJacket!]

Just another suggestion to add to the list, but I mention this one because it happened to me in the past.  Check how your fuel line is routed and make sure it does not kink.  Mine did and would run great until the fuel line softened up from the heat then would kink the rest of the way and plug off.

Also, it could possibly be the fent in your fuel cap.  No air going in means no or restricted fuel flow coming out.

And then there is always the old standby "Dirty Carbs".  It seems that no matter how good they are cleaned, they can always use another good and thorough cleaning.  Lots of little passages that can get blocked intermittently and make life miserable.

David