Throttle Balancing

Disco · May 20, 2020

So I've taken my bike to another tuner but we've discovered an issue. The throttles are out of balance and the front cylinder is maxed out while the rear is about 10-15% lower. This seems to be very high vacuum and the tuner is unable to get a smooth tune below 25% throttle.

Has anyone figured out how to balance the 1199 throttles? I've done plenty of carbs and one set of EFI throttles, but I can't even find a bypass screw on these.

Khmer1199 · May 20, 2020

Peculiar... when the bike is keyed "ON," the fuel pump primes, the ETV motors drive the throttle valves fully open and then return them to "X%" opening for startup. It's a system check during which the ECU validates operating parameters. If there was such a large disparity between the throttle bodies, I would expect a trouble code to be generated. If any problems arise with the throttle bodies, the manufacturer wants you to replace the entire throttle body assembly. To the best of my knowledge, replacement parts such as throttle position sensors, ETV motors, etc., are items which are not readily available. Pre-owned throttle body replacements, however, are usually easy to locate and relatively inexpensive. You may have to swap in a replacement to confirm your suspicions as everything is controlled electronically via the ECU.

Disco · May 20, 2020

Cheers Khmer. This is less about the sync and more about vacuum balance. Typically there's a bypass screw that allows air into the inlet port behind the closed throttle. These are really obvious on the V4 but seem absent on the 1199. I can see that the MAP sensor is pulling from a small port on the side of the cylinder head, but unless the ECU is adjusting the throttle at idle in an attempt to balance the cylinders I don't see a mechanical way of doing it.

Khmer1199 · May 21, 2020

Agreed... I believe it's all electronically controlled by the ECU. The only opening which extends into the throttle body below the throttle valve is home to the lower injector. Has the emissions canister been removed? If so, were the intake ports capped separately, or was the line to the canister plugged, leaving the tube running from one manifold to the other still in place. No vacuum leaks correct? How about putting a vacuum gauge on the manifold ports and comparing the results from both cylinders (idle, on the throttle, off the throttle, etc.)? Any reason to suspect compression issues? If you have MelcoDiag, hookup and reset the TPS and calibrate the MAP sensors to see if there's any change.

Disco · May 21, 2020

No reason to suspect compression, no smoke, great power - 185rwhp and good curve. The canister has been removed by the previous owner and the ports fitted with screws, so no pipes.

I haven't heard anything about calibrating the map sensors. The tuner is using Tuneboy and in touch with them, but they only agree that it's odd with no solution. The TPS has been done a couple of times. Interestingly when the MAP sensors were deactivated on the previous tune it ran smoother and I gained 20km/tank.....

Khmer1199 · May 21, 2020

That's interesting... not just the statement about the performance with the sensors deactivated, but also that the tuner hasn't encountered such a problem before, thereby preventing him from offering a reasonable explanation of the cause. There aren't too many "one of a kind/never happened to anyone else" problems... someone has likely experienced the same issue. Touch base with some other tuners to see if they can offer some feedback.

Disco · May 21, 2020

I pulled the map sensors out and the front one is full of fuel, pretty sure that shouldn't be the case......

Disco · May 21, 2020

Ran the bike in the following ways:

Both maps connected: idled as normal 1500rpm +/- 100rpm
Vertical with Map A disconnected: ran well
Horizontal with Map B disconnected: coughed, spluttered and stalled

With the Map sensors swapped:
Vertical with Map B disconnected: ran well
Horizontal with Map A disconnected: coughed, spluttered and stalled

So what did I get from this? The Map sensors are fine, but there must be something funky going on with the vertical cylinder as it runs terribly when only working from the vacuum in that cylinder. There is a very strong odor of raw fuel and the tuner did need to pump a lot into it to get the fuel ratio correct. The vertical did show a slightly lower vacuum compared to the horizontal, but it runs fine when based on the vacuum from the horizontal cylinder.

Any thoughts? I'm stumped

Khmer1199 · May 22, 2020

Disco said:
I pulled the map sensors out and the front one is full of fuel, pretty sure that shouldn't be the case......

Yeah, it's something to think about. I've never pulled a MAP sensor, or MAP sensor hose, and found fuel inside.

Disco · May 23, 2020

I'm going to go in search of a vacuum leak on the rear cylinder tomorrow. Seems to be the only plausible culprit

Disco · May 23, 2020

Hooked up a vacuum gauge to both map sensors and got a repeatable -24kpa on both cylinders, so no vacuum leak. The bike still stalls after 20 seconds when running on the vertical cylinder map sensor only. I'm wondering if there's either an ECU reading error or a wiring fault but both seem unlikely as it was giving a reading with the Tuneboy hooked up.

Khmer1199 · May 24, 2020

Curious to hear what you come up with. I would think that by disconnecting a MAP sensor, that your performance would be compromised, if not at idle, then at some point during operation. The ECU should receive an input from the sensors at start up to use as a baseline reference. Each time the vehicle starts, atmospheric conditions or the elevation may have changed. Having swapped the sensors and each one pointing to an anomaly in the same cylinder is telling you something. Fuel in the sensor may be telling you something as well, but as you indicated, that might be a result of the increase in fueling. And if that is the case, it's likely occurring at wide open throttle as intake and atmospheric pressures equalize.

Disco · May 25, 2020

More developments!

I swapped the map sensors and still got the same result: vertical map causes a stall, horizontal map runs well.

So I decided to change the vacuum source. I used the vertical map (including the electrical) for the horizontal cylinder and visa versa. The result was opposite - the vertical map with vacuum from the horizontal caused the stall. So regardless of what is connected to the vertical electrical connection it will induce a stall. This means that either the computer is not giving it receiving the right signal, isn't calibrated (if that's a thing) or the signal is being interrupted somewhere.

I did read some posts mentioning calibration of the map sensors, which seems plausible (much like the TPS) it's just a base voltage for the 0 kPa. Not sure how possible it is to change it, but if anyone knows, please let me know.

chris16 · May 25, 2020

not sure if they drift and need calibration.
what you can do is get a cheap scope and have a look at the signals.
should look like this at idle.

chris16 · May 25, 2020

and check gnd and vcc of the map

Disco · May 25, 2020

Pretty much the plan tomorrow, that and talking to the dealer to see if there's a reset available

Khmer1199 · May 25, 2020

Disco said:
Pretty much the plan tomorrow, that and talking to the dealer to see if there's a reset available

Glad you're making some headway. JP had a MAP sensor issue, last year I believe. If you have MelcoDiag, you may want to give this a try. It may offer further confirmation that neither MAP sensor is at fault, and that the problem lies elsewhere as you surmise. His post follows:

There is two map sensors on the bikes with the melco ecu
Generally when the sensor is defect , the engine run rich on 1 cylinder and stall time to time.

i've faced this problem recently and no dtc codes were thrown because electric characteristic of this sensor was good, but it wasn't sending any information to the ecu

how to check if your sensor is working:
1- start melcodiag and wait it finish to initialize
2- open passive test tab
3 - tick refresh in the frame where MAP V MAP H is displayed
4 - start engine

now as the engine revs , you shall see values of each map sensor been refreshed .

if the value is still the same , never refreshed , so your sensor is broken

Disco · May 30, 2020

Went over the wiring harness and found high resistance in the vertical cylinder MAP signal wire - 1.3ohm vs 0.2ohm on the horizontal. Cleaned it up and got it back to 0.2ohm. The bike doesn't stall with either MAP sensor disconnected, but will benefit from the retune on Friday.

rikkie07 · May 31, 2020

Hey, disco, I don't know the fueldelivery from the 1199 by head but does the fuel pressure regulator has a vacuum connection on the intake manifold? If so then check this for fuel, if fuel is inside then this is most problably your problem ( membrane is leaking fuel in the intake under vacuum). Did the tuner need to use a larger InjectorPulseWidth then normal or a smaller one to get AFR in the window on idle?

Disco · May 31, 2020

The only vacuum ports on the heads are to the MAP sensors and the EVAP cannister, which is removed and sealed up.

I'm pretty sure I've solved the issue and it was all electrical, but we'll see on Friday

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