F650 engine problem. Any advice?
 

Hi,

I ride a BMW f650 funduro, model 1999.

Currently I am in Kathmandu, Nepal, travelling from the Netherlands to Australia. The bike has problems which I describe below as accurate as possible.
1. The engine suddenly loses power, rpm falls back to stationary level but the engine stays running. This happens frequently but unpredictable. *
2. Opening the gas throttle has no effect on the rpm. Rpm stays on stationary level, engine gives some hard "bengs".
3. The only solution is to shut down and restart the engine. The problem seems to be solved but returns shortly after.
4. The problem as described appeared for the first time after a passed a major pothole. However I don't experience a relation between potholes/bumps and the occurance of the problem.
5. I had this problem leaving Sauraha (Chitwan NP) till the main road, a distance of about 6 km. The problem occurd maybe twenty times. However, being on the main road driving to Kathmandu the problem didn't occur. The next day, driving to workshop the problem was back again. So there seems to be some relation between the problem and the temperature of the engine.
6. I never had this problem before. *

Kathmandu Motorcycle Service Workshop has knowledge of European motorbikes. According to the mechanic the problem was probablt caused by failure of the carburators. So, they checked, cleaned and repaired the carburators. To no avail, *the problem persisted. Then we looked at the electric system, checked all wires and connections but found no visible damage. We measured the resistance of the sparks caps: 300 kilo ohm, which is much. So we replaced the caps with brandnew ones. The resistance of those caps was just 1 kilo ohm. I mad a testdrive again but to no avail, the problem was still there. After the testdrive we checked the resistance of the spark caps again. It was still 1 kilo ohm, so there was no electric pulse which damaged the caps. *

Has anybody a clue what causes this problem, what to do, how to go on? I am a bit desperate now!

Thanks, Mathew

Have you tried turning the throttle butterfly near the carb by hand?
It maybe that your throttle cable has popped out of the grip / snapped?

Also check that your spark plug isn't bridged (as in debris closed the gap of the electrode)

A bms-c reset might help too but it sounds like the throttle cable may well be (hopefully for you) the problem.

You need to go back to basics here... Unfortunately, I know SOD ALL about this model specifically.

Check everything methodically...

Fuel.... Check the filter. Are the vacuum pipes clear. Is it flowing freely.

Spark... Earth the plug to the frame and rev the engine.. Does it keep sparking ?? Is it a constant and rapid spark ?

Air filter... Clean ??

Carb ... All the vacuumn hoses intact ? Can you move the throttle by hand ??



The way you say that it comes and goes makes me think it's either electrical or a fuel delivery problem.

I'm guessing Fuel ...
 

I would check fuel flow out of the fuel tank. Also check for WATER in fuel tank. The petcock filters (they live inside fuel tank) may be clogged. easy to take out and clean!

Also, the Carb (or Carbs? Did the Funduro have ONE or TWO Carbs? :confused1: may have some sort of small inline filters at the fuel inlet point ... or? Sometimes are clogged. Go on line to BMW Funduro owner site and ask questions.

Drain float bowl(s). Remove pilot jet(s) and very carefully clean. have a very close look as the passages are TINY and may be clogged or have Varnish build up. Replace PILOT JET(s). Also pull Main Jet and any other jets and carefully clean ALL internal passages. Blow out with compressed air.
Do NOT lose any little parts. Go slow. THINK.

Make sure float needle is not clogged with debris (the float actuates the float needle and it then releases fuel into float bowl. Crap can get under the float needle contact point and clog. Float needle is a little pointed thing with rubber tip.

If you have a steady spark then must be fuel. Replace spark plugs if uncertain about them.

Good luck and thank goodness it's not fuel injected. Carb repair is cheap by comparison. bier

Agree with Ted. Sounds like you are either not getting enough Fuel to engine or your spark is failing under load but idling ok.

Start with Fuel flow. Change the Fuel filter.

Then try Change the air filter

Try Change spark plug

Try n swap coil

Does your model have a mass air flow sensor? it could be sending a wrong signal to the bms. Some after market filters rub oil on them, not good, or the connection has jarred loose, it's on the "snorkel" 6 inches or so underneath prior to the air filter intake. Easy to pull out and clean, worth doing even if it's not your problem. Caution, use good electrical cleaner spray.

Hi Mathew
Suggest you e-mail your BMW service company in the Netherlands and describe your problem as they may be able to give you options to work through. It sounds like a jet blockage from bad fuel, even though you have had them cleaned the work may not have been done correctly did the workshop in katmandu use plenty of carby cleaner? Good luck-Bruce

good morning i have the same problem with mine funduro f650 (1996), have you found the solution? thank you .

The thread is 7 years old so if the OP didn't reply I doubt they will now.

All the suggestions above are valid.

I would add a compression test. These terrible old Rotax engines have weak head gaskets and automatic decompressors, so both a possible way to turn a 40 HP engine into a 10HP one. The decompressor thing in the head would make for an intermittent fault and be unfamiliar to Bullet mechanics in Kathmandu. Would tend to make a hissing noise though.

Also, try the Chain gang F650.com website, lots of info parked there in the FAQ section.

Andy

Problem solved
 

The problem was caused by the rectifier. It died. If the rectifier doesn't function properly, the voltage goes up. Beyond 16,5 Volt, the electronic ignition device shuts down and the engine rotation falls back to stationary level. It was the first time I and the mechanics of Kathmandu Motorcycles Service faced this problem, so it took us a while to find out. The problem was probably caused by overheating of the rectifier. I bought a new rectifier and the mechanics improved the cooling by placing the rectifier on an aluminium plate.

Thank you very much
 

thank you