Poor Low Speed Running

[Desdinova]

if the oil or air temp sensor thinks it's really cold wouldn't the computer spray more fuel into the mix?

 

If that's how they work.. that's possible. If the sensor is dead, that would likely = cold. That is also something that would just go south overnight, or I assume a bad connection would have the same result.

 

I was also thinking the ground from the battery where it attached to the frame. This was a somewhat common item on a batch of Victory bikes. They didn't scrape the paint to get a good metal to metal contact where the ground attaches from the battery to the frame. The symptom is similar to what I have going on, so I did a cursory check, but I'm in the process of putting checklist together based on input here and give it one more serious go this week sometime before throwing in the towel.

 

Thanks... I'm liking the sensor theory so far the best.

[dlaing]

The instructions posted on this forum caution you to ensure that the fast idle cam is relaxed fully. However, upon closer examination, I found the small cam roller was still in contact with it's stop, even with the fast idle lever (and cable) fully relaxed. However, the throttle butterfly was still NOT fully closed.

 

There is a small screw on the RH throttle body, head facing downward, that indexes the fast idle cam roller. I released this screw, which allowed the throttle butterfly to close fully. I then tightened the screw so that there was just a very small clearance between the cam roller and it's stop.

Desdinova,

Did you make sure the cam roller was not in contact?

I usually slide a piece of paper through to ensure there is a gap.

Maybe I need to photograph this technique.

 

If that is not the problem, the Micha method or variant there of will probably get it running better.

Set bypasses to 1 turn out.

Set the idle to 1150rpm.

Balance.

Forget about the disconnected 150mV and set the at idle TPS reading to 500mV.

This may get you close enough.

If close enough, reload the PCIII map for your mods, test ride, try the voltage a little higher or a little lower and see if it improves.

 

You might still have an airleak that is causing problems??????

[Desdinova]

Desdinova,

Did you make sure the cam roller was not in contact?

I usually slide a piece of paper through to ensure there is a gap.

Maybe I need to photograph this technique.

 

If that is not the problem, the Micha method or variant there of will probably get it running better.

Set bypasses to 1 turn out.

Set the idle to 1150rpm.

Balance.

Forget about the disconnected 150mV and set the at idle TPS reading to 500mV.

This may get you close enough.

If close enough, reload the PCIII map for your mods, test ride, try the voltage a little higher or a little lower and see if it improves.

 

You might still have an airleak that is causing problems??????

 

Could you do a picture of the bottom facing screw on the RH throttle body. The only thing I see is the pivot point assembly for the CAM.. and we may be onto something here. Still not sure why it would go from fine to crap overnight, but one thing at a time as they say.

 

Although probably hard to glean from all the above, setting the TPS to read 500mv at idle and having an idle lower than 2000 rpm just isn't possible. Forget balance and forget even opening the Air ByPass screws, that's only going to increase the idle from 2000rpm. Again, all this pointing at this other screw you speak of.

 

If you can get a picture with a little photoshop labeling... that would be cool. (yeah, I know... not asking much). I will take all of this and put into a definitive tech article one done.

 

It still may be a combination of things... remembering that it was running fine.. then one morning.. just didn't.

[Tom M]

Although probably hard to glean from all the above, setting the TPS to read 500mv at idle and having an idle lower than 2000 rpm just isn't possible. Forget balance and forget even opening the Air ByPass screws, that's only going to increase the idle from 2000rpm. Again, all this pointing at this other screw you speak of.

 

It still may be a combination of things... remembering that it was running fine.. then one morning.. just didn't.

 

Your bike will probably run fine with the idle TPS set to 500mv if you follow "the Micha method" below. The key is to get the bike to idle nicely at 1100 rpm with both bypasses turned out 1 turn, then loosen the TPS screws and set it to 535mv. Your idle won't budge when you reset the TPS this way. I say use 535mv because that's 3.6 degrees according to the chart here.

 

Micha method

Step one - Set your valves to world settings

Step two - Set your bleed screws to open 1 full turn

Step three - Synch throttle bodies at just off idle (around 1800 rpm)

Step four - Set idle to 1100 using left idle screw adjuster only

Step five - Set TPS to 3.6 degrees

Step six - Ensure idle trim is set to zero

 

Here's the thread where this info came to light: http://www.v11lemans.com/forums/index.php?...=13188&st=0

 

That said, if your bike was running fine one day and lousy the next, it seems like something went bad. Maybe your TPS is dying? I think Dave has posted TPS curve here before. You might want to check it with a volt meter to make sure it's in range.

[Desdinova]

Thanks Tom, good points..

 

The issue is as you noted, "it just happened", was commuting to work every day, then it was actually on the way home one day that it was a bear to start, then the next morning... it started, but I couldn't go...

 

- idle @ 1100rpm isn't going to happen with 3.6 degrees (or 500mv) that's going to be around 2000rpm +

 

If I back off both idle screws completely.. then just turn the left one in (I've tried this with only the right one too), she'll hit 1100rpm at about 200mv, basically at 1 degree. I'm thinking something got out of wack with this other "bottom facing screw" that was mentioned...

 

And to be clear... the idle and revs and carb balance are fine in Neutral. Bike sounds great, idles great, runs great.... starts easily.... . until I try to ride.

 

 

-mkb

[Tom M]

If I back off both idle screws completely.. then just turn the left one in (I've tried this with only the right one too), she'll hit 1100rpm at about 200mv, basically at 1 degree.

 

I think you may be misunderstanding the micha method TPS adjustment. With both air bleeds set at 1 turn out from fully seated use the left idle screw to set your idle to 1100 rpm. Now loosen the TPS torx screws and turn the TPS until it reads 500 - 532mv. I doubt this will fix your problem but it should allow you to get to the 500mv idle target.

[Desdinova]

Thanks Tom, I get what you are saying. It can't hurt and is easy enough to try. The result may be another clue to the underlying issue.

 

Thanks

[motoguzznix]

Desdinova

 

some suggestions:

Check first the voltage across the battery - also when you try to start with the gear inserted. Maybe there is a short in the circuit that lowers the voltage when the side stand is up and the gear in.

 

Are you sure the ECU and coil/injectors get enough volts to work properly? Both are actuated via two relays and these should be checked first.

The relays get the voltage from fuse F1 and F2 - check if tension is lost in the relays.

 

As some people prior to me supposed: if the idle speed is that high, maybe air can intrude into the intake system .

 

My last suggestion: An exhaust valve or seat may had cracked. Perform a compression test or better: set the piston on closed valve TDC (as for valve gap checking), connect the compressor (0,5 - 1 bar) via the spark plug hole to the compression chamber. Pull the exhaust tubes and listen to a whistling noise. If the valves leak you can detect it easily.

[Desdinova]

I was busy with other things this weekend but I did get to check that "cam stop" that was mentioned.

 

I guess it just didn't sink in. Mine is fine. It's the fast-idle cam and there is a bit of clearance, it's not touching, although I could easily see how setting the fast idle cable could muck things if if one wasn't careful.

 

I also on close inspection see some faint cracking of the intake boot, on the side of the throttle body facing the route up to the air cleaner. While it's really mild, I'll replace it in the process of checking this out.

 

Anyway... thanks for the tips.

[raz]

I also on close inspection see some faint cracking of the intake boot, on the side of the throttle body facing the route up to the air cleaner. While it's really mild, I'll replace it in the process of checking this out.

I take it you mean the boot between TB and airbox. A faint crack there wont affect the engine.

[Desdinova]

I take it you mean the boot between TB and airbox. A faint crack there wont affect the engine.

 

Yep... I agree... grasping for straws at this point.

[raz]

If I read your posts right, both cylinders suddenly went crazy. That speaks against air leak a little. Did you check the mentioned temp sensors? You can measure them with any cheap multimeter. If the resistance is something like 2-4 kΩ it's fine.

[raz]

Another idea just hit me... maybe you should check your fuel pressure? A too low pressure might fit all your sympthoms. I'm thinking pressure regulator went bad, letting too much fuel pass it back to tank. Another reason would be clogged fuel filter. You can hear that if you know the normal sound from the pump.

 

Any little car repair shop should be able to test your pressure. It should be 3 bar = 44 psi.

[Desdinova]

Otay!!!

 

As I have several times in the past, I got the bike running today, but this time I had the PCIII out of the loop just in case.

 

I got it to run, idle was still high (1700 rpm) , carbs balances, 501mv, PCIII not in the mix.

 

I then brought up the VDST Software and low and behold, the trim is at -45!!!! That just didn't seem right so I zero'd it.

 

Hmmm bike runs a little better... lets try bringing that idle down with the bypass screws now and see if goes to heck as it has the other half-dozen times...

 

Nope... this time it's fine. I can achieve idle at about 1100 rpm, 500mv, 3.4% throttle, balanced carbs.

 

However, with Stuchi crossover, open airbox and FBF CF Pipes.... we need the PCIII back in the mix.

 

This is going to take some work, because the PCIII was set up (a few years ago) with the trim apparently at -45. The TPS was not set up properly either, which is why they probably adjusted the trim. I was pretty proud of the results I had got once I dynoed the bike and did my own balancing, but now that I have the TPS where it belongs, and the trim at zero, the PCIII map is essentially worthless. It runs sortof ok with the PCII zeroed out, but it's not great.

 

It's now off to find a DynoJet Tuning center that will touch a non-Harley.

 

Off for a test ride now.

[motoguzznix]

Otay!!!

 

As I have several times in the past, I got the bike running today, but this time I had the PCIII out of the loop just in case.

 

I got it to run, idle was still high (1700 rpm) , carbs balances, 501mv, PCIII not in the mix.

 

I then brought up the VDST Software and low and behold, the trim is at -45!!!! That just didn't seem right so I zero'd it.

Desdinova

 

The fuel trim should be adjusted with a COmeter in place - around 3.5 % on a bike without catalyst works fine. Just zeroing it cannot be the right solution as you don't know where the figure really is. Adjusting the trim +-3 makes a substantial difference in the CO reading. With the CO adjusted correctly there may be no need for the PC to make the bike running fine.

 

Normally a PC map works correctly in a properly tuned engine. Setting the trim so far from zero to get it running shows how far from the truth the map really is. I would not bother with it for any longer. Look for a proper map for your bike - there are sources in the forum to get the right one.