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Hi Dennie and Pete,
My bike splutters with just a fraction of throttle open too, but it will go. That is until I rev it further and then it really sounds bad, like knocking or something and then most likely dies.

Pete, is BMS battery management system?

So would a crankshaft sensor fault come if the timing was out? Maybe I bumped the chain when checking the valves, though I did zip tie them.

Haven't been out to check my bike yet. It's pissing with rain here (we're currently flooded in) and my shed can be miserable with all the rain dripping through. I live inland from Cairns (Julatten), flooding is common and not a big problem.
Oh, and I don't have a compression gauge, I'll need to get to town when the flooding goes down and get one.
Cheers,
 

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Hi Dennie and Pete,
My bike splutters with just a fraction of throttle open too, but it will go. That is until I rev it further and then it really sounds bad, like knocking or something and then most likely dies.

Pete, is BMS battery management system?

So would a crankshaft sensor fault come if the timing was out? Maybe I bumped the chain when checking the valves, though I did zip tie them.

Haven't been out to check my bike yet. It's pissing with rain here (we're currently flooded in) and my shed can be miserable with all the rain dripping through. I live inland from Cairns (Julatten), flooding is common and not a big problem.
Oh, and I don't have a compression gauge, I'll need to get to town when the flooding goes down and get one.
Cheers,
HI Baz the BMS is the computer that runs the engine, sometimes referred to as the BMSC.
It gets signals from the Idle air valve, the throttle position sensor, the crank sensor and the oxygen sensors and then decides how much fuel to give the bike.
One easy thing you could try is to disconnect the voltage regulator. Just unplug the plug that has 3 wires ( that comes from the alternator) and the one that has two wires ) that goes to the battery.
Then start the bike and see if that makes any difference to the running. That will tell you if the rectifier/regulator is overcharging and causing your problems.
There are two different timings.
The valve timing is set by the timing chain that comes from the crankshaft and goes up to the camshaft. It has to be spot on or you can up putting a valve through the top of the piston. Only ever turn the engine in its normal direction of rotation when checking that the timing marks on the camshaft sprocket line up correctly. It is good practice to turn the engine over a few times by using a socket on the crankshaft or by putting the bike in gear and turning the back wheel.
Then there is the ignition timing. It is set by the crank position sensor, that sends a signal to the BMSC to tell the brains of the bike when to fire the spark.
Pete
 

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Hi again,
Thanks for that Pete. I thought it was called the ECU, I guess it is on some bikes. Anyway thanks for clarifying all of that.
So if tomorrow is possible I shall plan to check the rectifier as described first, then go from there. I'll report back.
Dennie hope you don't mind me jumping on your thread? If our bike does share the same problem I hope it helps whatever I find.
Cheers,
 

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Hi Dennie and Baz, here is some information on the crank sensor.
A "Plug and Play" replacement.

The 650GS has a single sensor to determine the rotational speed, crankshaft position and the stroke. The sensor operates on the flywheel instead of the camshaft.

The BMSC engine management ECU measures variations in engine rotational acceleration to distinguish between the exhaust and compression strokes. The crankshaft slows down approaching the top of the compression stroke. BMW describe the sensor as a magnetic sensor rather than a hall effect sensor in the workshop manual.

The signals generated by the sensor are very small pulses which are difficult to measure with any low cost traditional test equipment which can lead to difficulties in determining whether the sensor is operational. In addition to this the on board diagnostics system in the engine management ECU does not always generate fault codes indicating the lack of detection of signals from the sensor. One fault code which can be generated is a speed sensor fault code which is not named well and can be misinterpreted as a rear wheel speed sensor fault. This can lead people to believe the BMS is faulty where the fault can be in the sensor.

The sensor operation can be impaired or fail where there is any metallic particle build up on the sensor. Potential sources of metal particles are the starter motor and the starter clutch, there would be more but those two in particular would be a source of ferrous particles.


Looks like inspecting the sensor first is a great idea. It appears to be a coil and magnetic pickup.
So as they say metal filings will upset it, also make sure the plugs and connections are good.
Check for continuity of the leads and sensor.
Pete
 

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Hi,
I might have got lucky, not sure as I'm still flooded in so I can't test ride it.
First I re-read all of the stuff on crossroadz (I had read it a year ago when this all started) but I never read this...
I read Bike Boys starting procedure and I just don't know if I was ever waiting long enough before. BMW don't let us know exactly how the ECU works resets etc so maybe this was all I needed to give the ECU time to do its thing.
BUT I also tried it running without output from alternator - no difference
Then I disconnected TPS and manually moved it while running and trying to match the throttle position. I did find that although I still got problems it wasn't as bad and I seemed to be able to make it run better at higher revs. At least with it left on idle and then manually moving the TPS and having the bike respond confirmed the TPS wires are good all the way to ECU.
Then I put it back together and run it, it seemed to work ok but I was afraid to push it. One reason was because I was never sure the oil was at the right height. I followed the procedure exactly as it was here...
Bmw G650x Challenge Oil Change Proceedure | RVB Precision
but somehow I still think I had way too much oil in it as I was getting a lot out of the sump pressure relief (I know this because I forgot to reconnect the airbox tube for the first run).
Anyway I run it until it was bloody hot (fan on for more than a minute and then rechecked height. It was way to high and seems a little brown and milky with lots of tiny air bubbles. The bike did sit for about a year and I did notice the coolant had gone down a bit before the first start, so I added a little water. The oil was new about a year ago when I did the change and like I said it has just sat while life got in the way for a year.

Anyway, before I drained a bit of oil it seemed to be revving ok, then after it was running the same but just sounded like it didn't have to work so hard (maybe I am imagining that).

So Dennie, make sure you are starting it like the bike boy says.. and I think it got better after doing this a few times. Maybe resetting it a bit each time???
I'll test ride it asap and let you know how it is.

Cheers
 

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Hi Baz as far as oil level goes, the procedure is to get the engine up to operating temperature, then let it idle for a minute or so. Then turn it off and check the oil level.
It is a bit of a dark art really.
The best way to make sure the oil is right is to change it, change the filter and put in the recommended amount.
The engines are pretty good on oil consumption and rarely need any topping up.
Hope you have found the problem. Seems that the odd starting procedure where you have to wait until the brains of the bike get a handle on what is where gets a few people.
Pete
 

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Discussion Starter · #27 · (Edited)
hi Baz and Godoh. About oil - I did it not for first time, also if oil is exceeding then it go to air box, so if there's no oil in air box - all is ok.
Crankshaft sensor was inspected visually, but I cannot test it other way that by resistance - it's ok, I believe it's only possible to fully test it by dealer computer.. new sensor is 300 $ and like a month waiting - looks too expensive to order it just for a test,
Also yesterday I tested TPS sensor on board, measuring not resistance but voltage - all looks perfect. Tried to move throttle as slow as possible, so it's only one digit from .xx volt changed one by one - all is good, no spikes/cut outs, so I believer TPS is totally ok. it goes from 0.3 to 3.4 volts.

Starting procedure - honestly I do exactly like it described every time since I own the bike.
 

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Hi Dennie, seems that you have checked everything possible. The crank sensor sounds expensive for something that is just a piece of steel and a coil. The only way that I could think to test it is to use an oscilliscope to look at the waveform when the bike is running. I am guessing that is out of the question for you in your situation.
TPS sounds like it is working, sorry I wish I had more knowledge of those bikes.
I hope you find the problem soon
Pete
 

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Hi Dennie and Pete,
I was able to have a quick short test ride yesterday and my bikes seems to be working fine now. Over the weekend I'll fix a few things like clutch switch, headlight, rear brake, then put it back together and have a proper ride.
Dennie my TPS was definitely going to over 4V, I wonder if this difference could be causing trouble. What if you remove the TPS from the bike, but leave it connected. Start the bike and see if manually moving the TPS you can 'match' the sensor to the throttle, and see if this can improve the running of the bike.
Cheers,
Baz
 

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Discussion Starter · #30 ·
And I got to dealers now.. they checked my bike , and my crankshaft play is above 0.2 mm. And this can cause crankshaft sensor errors. Looks like I need a new engine.
 

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HI Dennie, sorry to hear that it is a bigger problem like that. It could just be that the crankshaft bearings are worn.
It may be possible to strip the engine and change the bearings if the rest of the engine is in good condition.
Depends on your mechanical skills, other than that another engine from a wrecked bike would be a reasonably cheap way to go.
let us know how it turns out, and
Good luck, stay well and I hope the troubles with the invasion end soon
Pete
 

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Discussion Starter · #33 · (Edited)
HI Dennie, sorry to hear that it is a bigger problem like that. It could just be that the crankshaft bearings are worn.
It may be possible to strip the engine and change the bearings if the rest of the engine is in good condition.
Depends on your mechanical skills, other than that another engine from a wrecked bike would be a reasonably cheap way to go.
let us know how it turns out, and
Good luck, stay well and I hope the troubles with the invasion end soon
Pete
There are not bearings, but bearing shells I believe. 150 $ for each.
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And these comes with crankshaft or must be individually selected. It's not possible here anyways, dealer don't have such parts and even if they order in - in current situation in Ukraine it will be like 3+ months of waiting.
Don't know what to do for now.
 

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Hi Dennie, yes i remember reading once that the original design by Rotax had ball bearings, but BMW had them changed the main bearings to shells.
It does seem strange that they failed so fast.
From memory you were riding along and all was going well then all of a sudden the engine failed and would not accelerate.
From my understanding there are teeth on the outside of the flywheel that the ignition pickup is triggered by.
I am wondering if the flywheel as come loose and that is what is causing the problem.
Also the flywheel is most likely on a tapered shaft, if it is there is a small woodruff key that keeps it in the correct position, if the flywheel is a bit loose the key gets worn, this allows the flywheel to rotate which throws the timing out.
I suggest that your next move is to pull the side cover off the flywheel side ( where the ignition sensor is) and carefully inspect the flyweel and shaft.
If it has come loose that would explain the sudden problem.
Good luck
Pete
 

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hi Godoh! Yes, I also think about this. And inspect/clear metal shavings there too.
Seem to recall, have a look at the sprag clutch(?) metal shaving may have originated from ? Stick on ignition pick up? I' m relying on memory, check faqs here for sprag clutch. As said unusual for main bearings to fail at such low milage
 

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Discussion Starter · #37 ·
Seem to recall, have a look at the sprag clutch(?) metal shaving may have originated from ? Stick on ignition pick up? I' m relying on memory, check faqs here for sprag clutch. As said unusual for main bearings to fail at such low milage
Yes will look there too. It's unusual if it's real mileage. From 77k km only last 8k km is my own.
 

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Hi again,
Bad news I'm afraid. I got the bike back together and even finished off small jobs like mounting new fork guards etc.
I test rode it to the nearest town today and for the first 10km it rode smooth and well. Throttle response was good and fuelling seemed almost perfect.
Then 1km from town (after giving it a little extra throttle) it started spluttering exactly like it would if a carby bike had run out of fuel, so I backed off and coasted in to the fuel station and filled up.
Then I got going again and rode gentle for the first 1km before opening it up to enjoy the power... and then it spluttered and died. I couldn't get it going again until it had cooled down for ten - fifteen minutes. Once going I rode it very gentle but it started to splutter (by this I mean it was like riding a bucking bronco, on, off, forward and backward) and then it died again. I got it jump started straight away and kept going (5 km from home now). But I had to try to keep the throttle at idle or damn near close to it otherwise it would splutter again. It died again and thankfully started again and I got home but never took the throttle much past fully off.

So... it rode well getting up to 120km/hr for 10km until I opened the throttle for more power and then it spluttered.
I rode home between 50-80km/hr staying in a high gear and letting the throttle remain mostly closed.

Any ideas?
It's a public holiday here now, tomorrow I'll ring the local mechanic but dollars are tight, so any thoughts are appreciated.

Thanks,
Baz
 

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Baz it sounds like a fuel issue. I would probably try taking the fuel pump out and checking it carefully.
They are known to have short wires to the pump that break.
Other than that you could get the fuel pressure checked. But that would probably be more expensive than replacing the pump.
If you take the pump to an autoparts shop and ask for one the same it will cost about $40. If you try and buy one from BMW they will want to sell you the filter pump and mount in one piece for $700 odd.
I would just replace the fuel pump and see.
Clean the injector while you are at it,
The next step in fuelling is the fuel pressure regulator. They seem to be more expensive so I would suggest the pump first ( autoparts one) and clean the injector to see what happens then.
Pete
 

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Hi Pete,
I just thought to myself, the first place I broke down today was outside my mate Pete's place. He's real good with carby bikes, but not with FI unfortunately. Anyway...
I did take the fuel pump out of the tank a year ago when all this started as well as clean the injector. Thing is though, other than check wires and see that it does pump fuel to the injector body, I couldn't test anything else. I didn't replace it because it was $700.
I wanted to buy a BMW checker thing (plug in thing?), but they are also $$$. I will see if the mechanic has one and could do a quick check before I pull the pump. You think this a good idea or are you believing the pump has a high chance of being at fault?
Cheers.
 
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