Gas delivery problem after a few miles

[dewane]

Hi,

I have an '83 R65. Have had all kinds of problems with the left carburetor but have rebuilt it and have a new float and needle as well.

I'll be riding down the road at a good freeway speed and it starts to feel like it's running out of gas. This could happen after two miles, or after 10 miles.

I've adjusted the float height and have also pulled the tank cap - ever felt an engine when there is no hole in the tank cap and it slowly runs out of gas until you get more flow? It's EXACTLY that kind of feeling. None of these has helped.

I'll roll off the throttle, wait maybe 30 seconds, than it's OK until it does it again in two to 10 miles.

As noted, I've had all kinds of problems with the left carb and I think it might be leaking. An odd symptom for this though??

I'm having to put this into service as a daily commuter and it's about 40 miles each way. Right now it's extremely dangerous to ride it like this and will take the car until I get it sorted.

I also got gas all over my hand when attempting a float height adjustment on the way to work today. I don't want to be rear ended, or set myself on fire either - I'm very serious, even though it sounds like a joke. Second and/or third degree burns and several weeks in the hospital are not a joke.

Thanks.

[Bob_Roller]

Have you checked the rubber diaphragms in the top of each carb .

They tear and get holes in them as the rubber gets non flexible with age .

Also, are you sure it's the left carb giving you this problem ?

Check the fuel line where it does through the air box for kinking and the like .

I'm assuming you have Karcoma fuel tap, the fuel line comes out of it at the three o'clock position .

If so, there should be a fine metal mesh screen in the fuel tank that goes over the intake tubes, may want to check to see if you have a clogged screen .

If you have a Germa fuel tap, the fuel line comes out at the six o'clock position, there is a 14 or 15 mm nut that screws onto the bottom of the fuel tap and has a barbed fitting for the fuel line .

Remove the nut and there should be a fine mesh plastic screen filter in there, check it for clogging .

[donbmw]

I also could be  a ignition problem. I have had my 82 R65 give me fits when it was acting like a fuel problem and it turned out to be ignition leads.

don

[montmil]

Have you checked the rubber diaphragms in the top of each carb. They tear and get holes in them as the rubber gets non flexible with age.

Dewane,

My 1981 R65 would display the exact symptoms you described. The issue would occur randomly but most often, with me, at 55-60 mph but not every time. Aggravating and, as you say, unsafe.

The problem was a tiny puncture in one of the carb's diaphragms.

I'd also confirm that the petcock's in-tank filter screen is not clogged. Also, fuel line is cheap. It's also prone to delaminate and flake within its i.d. Are you running a fuel filter?

If the issue is being caused by a fuel flow problem, there may be a small piece of the fuel line or debris lodged in the float needle's seat.

[raypond]

It could be the breather hole in the petrol cap is blocked. I've seen it happen on two bikes. With no air getting into the tank a vacuum is created that stops fuel flowing to the carbs. Just loosen the cap, it'll quickly tell you if this is the problem.

Cheers
Ray

[Julio A.]

Looks like the gas flow to the carburetors are restricted.
There is a lot of possible causes to this problem, and most of it are already stated above.

Clogged lines, jets, a torn diaphragm and a sticking float needle are likely problems.

My right side float did that once, it would float upwards and would refuse to get back down; result of a rusty pin.

[dewane]

Hi guys, thanks for the replies. The carb diaphragms are new. I did get a new tank, which points to a screen issue. It wasn't rusty but there certainly could have been some junk in the bottom I can't see. I transferred the old fuel tap to this new tank.

I did remove the gas cap and that wasn't it either.

I am definitely not sure that it's one carb or the other. Seems to affect both.

Fuel lines are new, and are clear, so I can see that flow is working, might just be really slow. I might just get some new lines and redo that. I do have an inline filter, one of those ones that looks like a toy top.

I also have a new dynacoil and leads and cap from Motorrad Electrik (sorry my memory fails me, forgot his name now). So that's probably not the issue. I have heard that all fuel problems are electric on these old boxer twins, and it still could be that, but will sort the fuel stuff first.

[Bob_Roller]

I don't think this would be your issue, but the ICU for the electronic ignition is located under the tank, it has a finned aluminum heat sink on it .

There is supposed to be a heat sink compound between the ICU module and the heat sink itself, to aid in heat transfer from the ICU to the heat sink .

Just a thought !!!!

A word of caution, there are ICU's with heat sinks bonded to them, you can't separate them, without damaging the ICU itself .

I don't know how to tell them apart, but we had one member here, where he got the two separated, but tore the ICU open, I think it was on a monoshock R65 .

[tvrla]

The thing to remember about the heat sink paste and cooling the ICU, is that the paste doesn't aid cooling or the connection. It's the metal/metal contact that transfers the heat. The heat sink paste helps fill the small voids and prevent corrosion. There is something that supposedly creates a better connection, but don't recall what it is.

In any case, the original paste could have dried out, and if it was really slathered on, could be really inhibiting the transfer of heat. So clean it off well and smear just a thin coating on one side. Remember, this stuff doesn't promote heat transfer, but inhibits it. So don't use much. In fact, it's a good idea to polish the two surfaces, even wet sanding them with fine paper on plate glass, then polish. The more contact surface, the better it cools.

And I agree, these symptoms could be caused by the ICU overheating.

[raypond]

In very round figures the bike will use 100ml of fuel a minute. If any less than that is getting to the carbs it will cease to proceed. It's a very easy thing to check and eliminates any doubts about screens, filters, taps or lines.

[steven m]

What is the orientation of your fuel filter?  Sideways or vertical?  It may be refilling too slowly.  You might try pulling it out of the system to see if the problem goes away.  If it does, voila...

[dewane]

Hi, fixed the problem this weekend. I pulled the line and checked the flow below the inline filter. It was a pitiful drip, I mean pitiful - I'm surprised it could run at all. Seemed like 10 ml per minute rather than 100ml.

The filter was vertical, past the bend - I have a petcock that is the one that exits at 3 o'clock.

So pulled the tank, checked the screen that covers the intake lines to the petcock. A few red things on the screen, maybe rust or a gasket that is deteriorating that I blew out with some canned air. Opened the petcock and everything looked fine.

Got some clear fuel line at O'Reillys and removed the inline filter. Just rode the 37 miles into work with nary a problem.

Total cost of fix: $2.60.  

I got the inline filter I removed at San Jose BMW - it was one of those ones shaped like a top, that have golden filtering material inside. My theory is that these are normally used with tanks that have two petcocks. Which is every model except the R65.

Thanks to everybody here for helping me to keep this old bike on the road! Especially Bob who ran down the possible issues, and others who shared their issues and theories as well.

Dewane

[Bob_Roller]

Good to hear that it was a simple fix, after a bit of work though .

Inline filters serve a useful purpose, but they can become a forgotten item after a while .

Wouldn't be a bad idea, to put down the date of your fuel filter change in your maintenance records .

[Rob Valdez 79 R65]

[split] [link=http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1334628513/0#0][splithere][/link][splithere_end]

[bruce_launceston]

Keep an eye on the internal filter screen, the red flakes could well be tank liner. It can start flaking off.

It's reasonably straightforward to reline the tank with POR15 or similar product and I think it is worth doing as it should prevent any corrosion along the bottom tank seams where moisture can sit inside the tank.