Continuing - So what did you do to your bike today...?

[Hooli]

A good project Hooli, reckon youll enjoy. Another Mate doing early 50s Matchless, hes having fun. The ones i look at, incredible part prices. 

I'm trying not to make it a project Grog, it's just for commuting & bad weather. It will get days out when I'm not in a HD mood but it'll never be a nice tidy bike without a total rebuild that isn't happening. I'm off work for the next two weeks, so I reckon by the end of next week it'll have all the niggles sorted & then can be used & ignored.

[T250]

I'd be surprised if both sensors were faulty considering they read the same Eric, it's a bloody strange one with your bike. Have you tried an exorcism?

yes, its got me stumped so far as sensors etc are concerned, they all seem to be working. Will do a valve clearance check at some point.

I think I would check and compare readings with the new sensors, we are talking small voltages and I wonder being nearly 1V out is upsetting the ECU?
Sounds like valves etc are okay as you said it ran okay with vac connected but sensor disconnected...

[Hooli]

I've no idea how those sensors physically work internally. But when the bike is running they are subject to pulsing of the vacuum rather than a steady pull. I'll take a wild guess & say it's a resistive track linked to a membrane, so the track could suffer the same wear as the TPS etc. I know I've had a TPS that tested fine, but didn't work when vibrated on an engine.

So yeah, like T250 says I'd test the new one out of interest to compare & try it. Like he says, I can't see it being the valves either.

[Eric GSX1400K3]

Thanks fellas, I'm of the same opinion. Will fit the new MAP once it gets here. Rechecked both signal wires to these sensors and both are sending 5v to the sensor, so no power loss / wiring issue as far as i can tell. 

I did note that the table in the manual refers to atmospheric pressures and the voltage range for each, yet the test requires vacuum pressure.  I went and plotted the values from the table and what I measured, and the lines were opposite, so no way to check how they  correlated. 

Only reference point is 3.8v At atmospheric pressure, both IAP and MAP check out, and the fact that for both the voltage drops as the vacuum increases.

This does not exclude that one is faulty, as a broken wafer
inside  could give weird readings.

From Google: , see the AI response to my question.  I suspect that a faulty MAP could be caused by a cracked silicon wafer...

A MAP (manifold absolute pressure) sensor works by measuring the air pressure, or vacuum, in the engine's intake manifold and converting this measurement into an electrical signal that is sent to the engine's control unit (ECU). This information allows the ECU to calculate the optimal amount of air entering the engine and, in turn, determine the correct amount of fuel to inject for efficient combustion. The sensor's internal silicon chip deflects due to changes in pressure, which alters its electrical resistance and output voltage, allowing the ECU to accurately manage the air-fuel mixture for smooth engine operation.
 

How the MAP Sensor Works

1. Pressure Measurement:

The MAP sensor is connected to the intake manifold and monitors the pressure within it. When the engine is running, it creates a vacuum in the manifold; the degree of this vacuum varies with engine load.

2. Diaphragm Flexing:

Inside the MAP sensor, a small, flexible silicon chip or diaphragm is exposed to the intake manifold's pressure.

3. Resistance Change:

When the pressure changes, it causes the silicon chip to flex. This flexing alters the sensor's electrical resistance.

4. Voltage Conversion:

The sensor converts this change in resistance into an electrical signal.

5. ECU Calculation:

The ECU receives this electrical signal and interprets it as a specific manifold absolute pressure. It then uses this data, along with other inputs like engine speed and air temperature, to calculate the precise air-fuel ratio needed for optimal performance.

How This Information is Used

Fuel Injection:

The ECU uses the MAP sensor's data to adjust the amount of fuel injected, ensuring efficient combustion and preventing issues like a rich fuel mixture.

Ignition Timing:

The sensor's readings also help the ECU control ignition timing for better engine performance.

EGR System Control:

In some cases, the MAP sensor provides feedback on the operation of the Exhaust Gas Recirculation (EGR) system to the ECU.

Factors Affecting MAP Sensor Readings

High Manifold Pressure:

When the engine is accelerating or under heavy load, manifold pressure increases, causing the sensor's chip to flex upward, resulting in more fuel being injected.

Low Manifold Pressure (High Vacuum):

At idle, the manifold pressure is low, creating a high vacuum. This causes the chip to flex differently, signaling the ECU to provide less fuel.

This endeth today's science lesson...

[grog]

Good explanation Eric,lets hope it fixes Bilbo. Hooli, unexpected buys thru my life have been probably up there with the best, still remember as great bikes.Two of my favourites,used day in day out, never cleaned, maintenance only when necessary 1974 Z1 Kawa, 1975 F1 Honda.

[T250]

Good info Eric  perhaps this might explain some of the rough running people have experienced, myself included, just off tickover poodling through traffic, but get an incline at same throttle opening putting more of a load on the engine and it all smooths out due to the flex of the chip inside the sensor and different vacuum? I often wondered about that after chasing STPS, TPS settings and throttle body balancing, also the sensor sits right above a hot engine, which as the sensor ages could affect the silicon/operation?

[Eric GSX1400K3]

Maybe T250, the strange thing is the IAP sits in free air, relatively cold and shows the same values.  Perhaps an age thing, they are 22yo sensors I suppose.

[Hooli]

I know you said you checked 5v to the sensor. Did you also check the middle (yellow?) wire has continuity back to the ECU when when you flex the cabling about? same with the earth. Either could be causing the sensor readings to vary due to vibration when the bike is running.

I suspect the sensor will fix it though, seems to be a thing that you prove a sensor is faulty, it tests ok but a new one works.

[Hooli]

I found out yesterday why the snotter is a slightly slow starter & the last owner suspected the battery, the one fitted is too small. It doesn't give a great health reading on my battery tester either, so I'll replace it at the weekend when I do some other jobs on it.

I need to order a USB/voltmeter thing like I fitted on my Hornet as I'm bound to want the twatnav on there at some point. Lucky there's loads of flat spots on the fairing to shove it in & be easy to see.

Think I'll be stripping the brakes down to clean as well, the front is excellent as I proved when a van appeared in front of me from a layby as I came around a bend too fast. But the rear feels weak & disappointing. It's linked brakes so feels slightly odd, but I want to check them so I know they're ok.

[Barbastro K6]

Another topic, I have fixed the two tank round rubber front  with contact glue because they continuously fall off when handling the tank

[grog]

Agree Barbastro, stops them running away. Rubber grease on side cover grommets also another help.

[Hooli]

Another topic, I have fixed the two tank round rubber front  with contact glue because they continuously fall off when handling the tank

They are escape experts too. I lost one once, got another off someone on here & about six months later the original one appeared in the middle of my garage floor. It obviously got bored wherever it was hiding.

[Hooli]

Snotter job list update, mostly for my own reference.

Indicator switch, it often doesn't work turning left. It'll be full of shit, I've seen that before.
Gear lever to move down a bit.
Get allen bolt M8? To fit nearside mirror.
Replace battery with one the correct size.
Get relay and make ignition switched aux feed up. Use to power grips, jacket, usb socket that's on it's way and aux lights that are also coming.
Try to find why it's crabbing, loosen the front end and wriggle it incase it's twisted.
Fix fuel light.
Fit scottoiler.
Clean callipers as rear brake is shite. Change brake fluid as it looks antique.
Lube throttle and cables so it's smoother.

Fit crash bars, aux lights and usb socket when they arrive.

I think that's it. Nothing major there just lots of little bits to make it nicer to daily.

[Hooli]

UPDATED Snotter job list update, mostly for my own reference.

Indicator switch, it often doesn't work turning left. It'll be full of shit, I've seen that before. DONE
Gear lever to move down a bit.
Get allen bolt M8? To fit nearside mirror. YET TO DO AS IT'S A M10 FINE WITH UNDERSIZE HEAD, BUT I HAVE A PLAN
Replace battery with one the correct size. DONE
Get relay and make ignition switched aux feed up. Use to power grips, jacket, usb socket that's on it's way and aux lights that are also coming. DONE
Try to find why it's crabbing, loosen the front end and wriggle it incase it's twisted. FRONT STRIPPED & REBUILT WITH FORKS TURNED 180 DEGREES, NEED TO TEST RIDE
Fix fuel light. PROVED IT'S THE SENSOR, NOW TO SEE IF THEY ARE STILL AVAILABLE
Fit scottoiler. DONE
Clean callipers as rear brake is shite. Change brake fluid as it looks antique. DONE, BRAKES FEEL EXCELLENT NOW
Lube throttle and cables so it's smoother. DONE, FEELS MUCH NICER
CLUTCH MECH IN SPROCKET COVER CLEANED & LUBED, THAT'LL MAKE IT A LOT LIGHTER & NICER TO USE

Fit crash bars, aux lights and usb socket when they arrive. HMM YEAH, THE CRASH BARS DON'T FIT (WRONG YEAR DESPITE THE ADVERT) LIGHTS DON'T WIRE HOW TO THE ADVERT SAID AND WON'T FIT WHERE I PLANNED EVEN IF THE CRASH BARS FITTED

Yesterday was annoying & not much progress. Seized bolts on the screen meant I couldn't get the clocks out as you have to go in from the top, when I finally got in the bulbs shown as replaceable in the manual are surface mount LEDs so that was a waste of an hour. Oddly though the fuel like works now when you short the wiring so maybe the multi-plug wasn't seated right.

I could put it back together but seems pointless if I can get a fuel level sensor in a few days & do it then.

[Hooli]

Smaller update. The sensor is still available, £133 here or £45 on Webike Japan. That's £65 delivered & well worth it compared to running out of fuel as there's no gauge either.