Anyone had any experience or advice on how to calibrate the fuel sensor for a K75? When I redid the tank I'm not sure which of the two sensors I put in but the low fuel light is coming on at 169 miles (271KM). At that point the bike will start surging as fuel sloshes around if I'm accelerating or if I'm going up a hill/incline. I would prefer to have the fuel light come on at around 150 miles. That's warning enough to get to a gas station. I suspect bending the arm float arm is one way to do it. But wondered if there were a more controlled approach.

best regards.

Use an appropriate lever to move the wheel if it's not frozen.
Regards Martin.

To expand on Martin's post, the controlled way is fully described in text and photos by robmack in this post then supplemented by a post by kennybob. Scroll down to find it. The condition of the sending unit will determine the ease of that method.

Surging is likely to happen on my K75 at ~215 miles. With a full gallon container of reserve fuel onboard, I've run the moto a few times until it has stalled; that's happened at ~225 miles. I set the fuel level indicator lamp to light at approximately 160 miles of mixed mountain and flatland riding then refer to the trip meter to determine how far my luck will stretch. Miles per gallon tend to range from 45 to 52, solo but I'm not frequently contending with grades common in the Bay Area. Exactly how much fuel remains after the lamp is lit depends upon how fast I've been riding, the head- or tailwinds and the pitch of the roads.

You should probably raise the float a little for earlier indication. Is your tank's fuel return outlet at the tank's ceiling emptying onto the right side of the tank? If it is, a hose can be attached to it then routed to dump on the left side of the tank nearer the fuel pump to wring out a few more miles from the supply.

Laitch wrote:To expand on Martin's post, the controlled way is fully described in text and photos by robmack in this post then supplemented by a post by kennybob. Scroll down to find it. The condition of the sending unit will determine the ease of that method.

Surging is likely to happen on my K75 at ~215 miles. With a full gallon container of reserve fuel onboard, I've run the moto a few times until it has stalled; that's happened at ~225 miles. I set the fuel level indicator lamp to light at approximately 160 miles of mixed mountain and flatland riding then refer to the trip meter to determine how far my luck will stretch. Miles per gallon tend to range from 45 to 52, solo but I'm not frequently contending with grades common in the Bay Area. Exactly how much fuel remains after the lamp is lit depends upon how fast I've been riding, the head- or tailwinds and the pitch of the roads.

You should probably raise the float a little for earlier indication. Is your tank's fuel return outlet at the tank's ceiling emptying onto the right side of the tank? If it is, a hose can be attached to it then routed to dump on the left side of the tank nearer the fuel pump to wring out a few more miles from the supply.

Hey guys, Thanks. Sounds quite reasonable. Maybe to look at the spare sensor and check it out first then swap it for the one in place.  My mileage on the silver bike is less than 40 mpg and that's with a T-windscreen. My Red bike gets 40+mpg and that's with a R100RT fairing with a barn door windscreen. The silver bike is a work in progress whereas Red has been my main ride for 163,000miles. I'm thinking there is some work to be done on Silver, like cleaning the injectors and work in the instrument pod. It's coming along. But hey thanks again. I'll be asking more questions about small details like the instrument pod. Waiting to get a LED replacement kit before tackling that.

Off-topic: do NOT replace the generator warning bulb with an LED. The alternator needs the filament resistance to kickstart power generation.

Dai wrote:Off-topic: do NOT replace the generator warning bulb with an LED. The alternator needs the filament resistance to kickstart power generation.

+1 No need to say why.

When I put LED's in my instrument pods, I take a pieces of black electrical tape and put a 1/4"(6mm) holes in them and place them over the blue and red lenses for the high beam and low fuel lights. Makes them less annoying at night when I may be riding for long periods with them lit, especially the high beam indicator.

Dai wrote:Off-topic: do NOT replace the generator warning bulb with an LED. The alternator needs the filament resistance to kickstart power generation.

In my experience using a LED in place of a traditional bulb in the charge indicator slot of the instruments only delays when the indicator light goes out. In fact, I don't have a bulb or an LED in Big Block's minimal dash at all and she begins churning out full charge just off idle, rising to 14.3V regularly. But hey, it's a beasty of a different sort anyway.

Now, on an Airhead (and perhaps early Guzzi) you absolutely need a functioning bulb in there before she'll even begin to think about charging.

Dai wrote:Off-topic: do NOT replace the generator warning bulb with an LED. The alternator needs the filament resistance to kickstart power generation.

Hi Dai, on this one subject I will disagree. I replaced all my bulbs with LED's on the Red bike including the alternator warning light. As per Scott Drake's comments about this If I rev the engine up to about 2000 rpm then there is enough power to get the alternator going and after that it performs the same as a bulb. And I've had this change in place for several 10's of thousands of miles without issue. Speaking of which I've not heard back from him. At last report he did not have the instrument pod LED's in stock. So I was wondering if there is any other sources. A friend
passed this link to me but I don't see them as providing the instrument pod lights.

https://www.superbrightleds.com/vehicle/1987-bmw-k75c-vehicle-led-lights?make=11&model=2854&year=1987

jjefferies wrote:At last report he did not have the instrument pod LED's in stock. So I was wondering if there is any other sources.

I think you're looking for a 194 wedge base single LED for that application (alternator lamp) but you can compare the one in Red's instrument with the selection at Superbright or other vendors.

Most electronic stores will have them as in Jaycar, Tandy. I tried blue backlighting and then settled on red. For some reason green LED's are expensive.
Regards Martin.

MartinW wrote:Most electronic stores will have them as in Jaycar, Tandy. I tried blue backlighting and then settled on red. For some reason green LED's are expensive.
Regards Martin.

Is Tandy the same company as Tandy, i.e. Radio Shack, in the US? And are they still in business down under?

One in the same, they used to be along with Dick Smith's all over OZ. There might be one or two left in OZ, Dick Smith evolved into a electrical appliance store and disappeared . All we have left is Jaycar and it's clone Altronics.
Regards Martin.

I get all my instrument LED's from Super Bright LED's. The wedge base single element 120 degree for the back lighting and the indicators.

https://www.superbrightleds.com/moreinfo/instrument-cluster-gauge/194-led-bulb-1-led-miniature-wedge-retrofit-car/197/852/

Point-Seven-five wrote:I get all my instrument LED's from Super Bright LED's.  The wedge base single element 120 degree for the back lighting and the indicators.

https://www.superbrightleds.com/moreinfo/instrument-cluster-gauge/194-led-bulb-1-led-miniature-wedge-retrofit-car/197/852/

Hey thanks, good pointer. What color did you get for the instrument pod back lighting? And does it work for you? Not too bright or dim? What about the alternator light? The kit I got from Scott had a red one which was adequate to energize the alternator as I mentioned previously. Just wanting to know if these have the same or similar  draw.

I've used red, blue and green LED's in my instrument clusters and they all work well. Only thing I've noticed is that the 1/10th mile digit on the tripmeter can't be read at night with the red lights.

I leave the bulb in the battery idiot light. I let my bikes idle in the garage during the winter to charge the batteries. With the LED, I was having a hard time keeping the rpm's high enough to self energize the windings in the alternator.

As you've (mostly) all found out, using an LED in the gen bulb position requires a big handful of revs to kickstart the charging. A standard bulb starts charging at about 900 rpm. If there's enough residual magnetism in the rotor then the alternator will stay activated at lower revs. You may get lucky and it stays charging at normal tickover. IME I found that charging dropped out at about 1100rpm. Didn't like that.

Dai wrote:As you've (mostly) all found out, using an LED in the gen bulb position requires a big handful of revs to kickstart the charging. A standard bulb starts charging at about 900 rpm. If there's enough residual magnetism in the rotor then the alternator will stay activated at lower revs. You may get lucky and it stays charging at normal tickover. IME I found that charging dropped out at about 1100rpm. Didn't like that.

Exactly!

Since the bulb is illuminated for very little time, it's life and current usage is not a factor. It's more important to me that the field is excited at low rpm when idling, especially during winter storage when the monthly engine idle in the garage is how I keep my batteries charged up.