Broken down in South America, I need help diagnosing my problem

[Brainrotting]

Hello, I'm new here (site recommended to me) so be gentle

Problem: Motorcycle turns over but won't start

Motorcycle: BMW F650 GS Dakar 2006 US import

Background.

The motorcycle now has over 60,000 miles on the clock
NB: To date I have not checked the valves/shims neither have I replaced the fuel filter

I have just ridden through Brazil where the quality of fuel is very low, possibly as low as 85 RON and I think it has a percentage of ethanol in it too. When I entered French Guiana and filled up with high quality fuel I immediately got over 30% more mpg. I was very happy!

In Brazil I had poor mpg, and I sensed that the bike had become sluggish in nature – it no longer had the same acceleration or torque, made me realise that I should get the valve clearances checked. I am aware that I should have done this sooner. Having never done it before I've been putting it off until symptoms like back firing occurred. I was hedging getting to Suriname or Guyana before doing it but I have now broken down. The bike hasn't been backfiring and the mpg and sluggish nature improved with the better quality fuel in French Guiana. I've not noticed any particular problems with starting the motorcycle.

Two days before I broke down I was riding in 3rd/4th gear and the bike surged and perhaps briefly cut out two of three times betwwen 3,500 & 4,500 RPM. When I stopped and switched the engine off I had problems restarting it. I could hear the Moditec unit making a whirring noise in between starts and I allowed 5 or more seconds before hitting the ignition button again. In between the starts I noticed that the rev counter would flick up in time with a noise form the Moditec unit and I assumed it was calculating air/fuel mixture etc. When I got home I reset the Moditec unit by disconnecting it for 20 minutes. Following this the motorcycle restarted on the third attempt and I observed what I consider to be normal behaviour as it calculated the air/fuel mix between each start.

The following day I went out on the motorcycle for an hour and stopped for 10 minutes. When I tried to restart the bike it wouldn't fire up. I eventually got some help bump starting it and all was good but I was now more concerned. When I arrived home I switched it off and it restarted immediately first time.

The next morning the motorcycle wouldn't start at all. It turns over but doesn't fire up. When I turn the motorcycle on I no longer hear any noise from the Moditec unit and it no longer appears to be doing any start up checks. The rev counter remains at zero in between restarts. The motorcycle wouldn't bump start, and I even got a very slow tow to see if it would start but the rear wheel just locked up and it wouldn't fire up.

I have checked the wiring loom, battery connections, air filter, all appears good. I have plenty of oil and there is fuel in the tank.

My thoughts are:

Valves... have I ****ed up my engine?
Are the fuel filter, pump or injector needles ****ed from the poor fuel in Brazil
Is my Moditec unit ****ed
Is the Brazilian fuel problem a red herring?

Thanks for your help.

 

[Micky]

Hi .... we were using very low octane in Mongolia and some of the Stans, the bike's, both 650 single GS's, ran rough, coughed and farted, but continued to run nonetheless.

While in Iran last year hooked up with a couple of guys, one on a 650 GS and he had the same problems as yourself. Turned out to be the prop stand kill switch ... it had died in the kill position. Remove the plug from the kill switch wire and short out with a paper clip, (red and white wire I believe) and see if it starts.

All the best

 

[Red Rock]

Hi Graham,
Sorry I can't offer any technical advice, but hope someone can help and get you on your way.

Look forward to your next instalment of Brainrotting on youtube. Great adventure, great channel!

Good Luck

 

[(RIP) Kaister]

it does sound like the sidestand switch - but if its not....

i know nothing about the particular engine, but from first principles i would say you don't need the valves looking at

all your problems will be fuel related ( you imply it turns over quickly and i would see no reason to suspect the battery )

all the problems started in a poor fuel environment - so don't get sidetracked .
The rev counter flicking is because it gets a signal from the ecu, i would imagine - and this is cos the bike is trying to start - again down to fuel problems

Sounds to me like fuel pressure related, or blockage in the fuel system / filter.

Can you get some 'easy start' spray can and spray it into the airbox to check it starts with this ?


rear wheel locking is normal during bump starting - don't worry - you're just not doing it right use 2nd gear,not first

 

[Sooty09]

The fuel filter is also the fuel pressure release valve. The pump is not like the modern clever things on later GS models and operates at full pressure, any fuel not required by the injector is bled off by a valve in the filter. Its a crap system and the reason the GS650 filter is £70.00+.
If the filter is very old and clogged the regulator valve could fail so the injector is not pressurised enough to atomise the fuel. Its possible the regulator works closed when left for a few minutes causing temperamental running.
The GS single forum or the international BMW riders club (The Chain gang I think the section is known as) will be able to supply first hand knowledge of this well known problem.
Its a part of the bike which should be changed at major services, If its 60,000miles old and running on poor fuel I would look here for the problem.
PS I have heard of new filters causing a similar problem to bikes which previously ran perfectly because there were a few bad batches with the wrong spring rate.
I have posted the help request on the GS singles section. Brainrotting if you are logging in here also check their section.

 

[Brainrotting]

Problem Diagnosed

Thank you all for your help and suggestions. Thankfully a lot of information came my way and it's helped diagnose the problem as a faulty fuel pump. There is no doubt that I will change my fuel filter and check the valves when I find somewhere suitable but now I just need to get a part imported and I can get on my way once more.

What a great resource UK GSer is

 

[Micky]

Thank you all for your help and suggestions. Thankfully a lot of information came my way and it's helped diagnose the problem as a faulty fuel pump. There is no doubt that I will change my fuel filter and check the valves when I find somewhere suitable but now I just need to get a part imported and I can get on my way once more.

What a great resource UK GSer is

Glad you got sorted Brainrotter

Keep us informed as to your travels ....