F650GS Single Spark 2000 a wee story

[ahebron]

A couple of weeks back Rhyna and myself set off on our bikes for a trip up country.
All going well till about 3 hours in and her F650 GS Single Spark starts to loose power which is a bit of a problem as there are a few hills to cover and it is standard NZ State Highway which is one lane each way. Eventually she pulls over with the bike running very badly. Call the AA and they take the bike and her home and I ride the faultless R1150GS home.
I do a bit of research and see the filter pressure regulator has never been changed and the bike is a 2000 model and has at least 115000kms on it so order one from Motorworks in the UK. In the meantime I decide to check the valves and find the exhaust a bit tight both at .203mm. Crank locked, timing at tdc and valve gear removed and new shims fitted. All good.
I fit an additional fuel filter inline with the new pressure reg/filter so it is cheaper to replace that than the pres/reg.
All good I thought but the bike wont start, pops, farts and smells of petrol. Double check timing and correct still wont start, then it starts after a bit of cranking and use of the throttle, idles smoothly and revs through the range but wont start after turning it off. Running a freshly charged car battery with truck jumper cables.

Frustration is setting in.

Decide to disable the decompression lever with a balled up piece of electrical tape wedged behind it so it is off and the bike starts first touch of the button. Remove the tape and the bike wont start, flick the decompressor with my finger on first rotation and it fires.
Maybe the starter motor is a bit slow so remove the starter and give it a thorough clean it just had the usual black carbon but everything else seemed ok, reassemble, fit it to the bike and it runs backwards

Take starter motor off disassemble and find a wee indent that I had out of whack, realign and hey it spins the right way but still wont start again flick the with my finger decompressor lever and it fires straight away.


I think I am chasing two different problems here
One the blocked filter that caused the bike to run rough, what came out of the filter was black and the filter was filthy inside. And maybe this was causing the fuel pump to overheat and run badly. I have experienced this on a BMW E36 318ti Compact I bought as non runner and the fuel filter was blocked which caused the fuel pump to burn out.
Two the non starting due to the decompression lever not disengaging with centrifugal force when starting. Either the starter motor isnt turning the engine fast enough, the decompressor is sticking but it feels very loose and the spring is still in place. Or we dont have enough engine compression.
Unfortunately my compression testers are for cars but I have just ordered one that will do bikes and small plugs.
I am bit concerned how I will do a compression test but think I will have to remove the decompressor and reassemble the bike to get it warm and do the test. I would like to leave the decompressor on but cant see how I can safely do this and make it start.


It was always a noisy bike to start but that seems to have gone away. But not the time it took to start.
I cannot see a reason why I cannot take the decompression lever off the bike as it seems to start fine without it.


So has anyone got any advice or helpful tips preferably ones that involve repairing the bike and not torching or driving into the sea.


Thanks
Adrian

 

[Deleted account 200123001]

Any chance of turning the text black it's a bit faint?

 

[GSaddict]

I think your ink cartridge needs replacing

 

[Packer]

Any chance of turning the text black it's a bit faint?

Highlight the entire post and read white text against blue background.

I'm confident that BMW would not have fitted a decompressor if it wasn't needed. Perhaps the exhaust valves have burnt a bit and you have low compression allowing the starter to spin the engine up and as the rev's increase there is enough compression for it to fire.

 

[Deleted account 200123001]

Highlight the entire post and read white text against blue background..

did that too.

 

[ahebron]

Give this a go
F650GS Single Spark 2000 a wee story
A couple of weeks back Rhyna and myself set off on our bikes for a trip up country.
All going well till about 3 hours in and her F650 GS Single Spark starts to loose power which is a bit of a problem as there are a few hills to cover and it is standard NZ State Highway which is one lane each way. Eventually she pulls over with the bike running very badly. Call the AA and they take the bike and her home and I ride the faultless R1150GS home.
I do a bit of research and see the filter pressure regulator has never been changed and the bike is a 2000 model and has at least 115000kms on it so order one from Motorworks in the UK. In the meantime I decide to check the valves and find the exhaust a bit tight both at .203mm. Crank locked, timing at tdc and valve gear removed and new shims fitted. All good.
I fit an additional fuel filter inline with the new pressure reg/filter so it is cheaper to replace that than the pres/reg.
All good I thought but the bike wont start, pops, farts and smells of petrol. Double check timing and correct still wont start, then it starts after a bit of cranking and use of the throttle, idles smoothly and revs through the range but wont start after turning it off. Running a freshly charged car battery with truck jumper cables.
Frustration is setting in.
Decide to disable the decompression lever with a balled up piece of electrical tape wedged behind it so it is off and the bike starts first touch of the button. Remove the tape and the bike wont start, flick the decompressor with my finger on first rotation and it fires.
Maybe the starter motor is a bit slow so remove the starter and give it a thorough clean it just had the usual black carbon but everything else seemed ok, reassemble, fit it to the bike and it runs backwards
Take starter motor off disassemble and find a wee indent that I had out of whack, realign and hey it spins the right way but still wont start again flick the with my finger decompressor lever and it fires straight away.


I think I am chasing two different problems here
One the blocked filter that caused the bike to run rough, what came out of the filter was black and the filter was filthy inside. And maybe this was causing the fuel pump to overheat and run badly. I have experienced this on a BMW E36 318ti Compact I bought as non runner and the fuel filter was blocked which caused the fuel pump to burn out.
Two the non starting due to the decompression lever not disengaging with centrifugal force when starting. Either the starter motor isnt turning the engine fast enough, the decompressor is sticking but it feels very loose and the spring is still in place. Or we dont have enough engine compression.
Unfortunately my compression testers are for cars but I have just ordered one that will do bikes and small plugs.
I am bit concerned how I will do a compression test but think I will have to remove the decompressor and reassemble the bike to get it warm and do the test. I would like to leave the decompressor on but cant see how I can safely do this and make it start.


It was always a noisy bike to start but that seems to have gone away. But not the time it took to start.
I cannot see a reason why I cannot take the decompression lever off the bike as it seems to start fine without it.


So has anyone got any advice or helpful tips preferably ones that involve repairing the bike and not torching or driving into the sea.


Thanks
Adrian

 

[ahebron]

Highlight the entire post and read white text against blue background.

I'm confident that BMW would not have fitted a decompressor if it wasn't needed. Perhaps the exhaust valves have burnt a bit and you have low compression allowing the starter to spin the engine up and as the rev's increase there is enough compression for it to fire.

An update
Today I removed the spring in the decompressor and the bike fired first hit of the button.
The decompressor is still operating but the spring that pushes it into the exhaust valve has been removed meaning the counterweight can flick it off at slower engine speed which allows the bike to start. This is still running it on a freshly charged car battery with truck spec jumper cables.
I can now get then engine up to operating temp to do a compression test when my new tester arrives in the next few days.

Adrian

 

[ahebron]

Todays update
Compression tested it engine warm, WOT and gauge reading 195psi.

With the decompressor spring removed the bike starts first hit of the starter button which is something it has never done before.


Adrian

 

[ahebron]

The bike is still running fine and starts first press of the starter button which is something it has never done before, it also drives a lot better with the engine smoother.
My thinking on this is that someone in the past has adjusted the valve timing slightly to possibly make the bike start better. I recall reading somewhere that someone stated BMW advised a timing adjustment at one time.
When I reassembled the timing after doing the shims I set the motor up as per BMW manual, I tried to do the cable tie the chain to the sprockets trick but that didnt work for me as the chain bunched on the main sprocket off the crank.
This is the only reason I can see for the motor refusing to start after the work I did.
It still has its decompressor but without the spring so it releases sooner, maybe the starter motor is a bit tired but it works kn ow so I will leave it till the next issue.

Adrian