F650GS 2002 Single Spark issues / mods / improvements?

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Thread: F650GS 2002 Single Spark issues / mods / improvements?

  1. #1
    Bike
    F650GS 2001
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    Aug 2018
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    Default F650GS 2002 Single Spark issues / mods / improvements?

    Hi Chaps,

    My F650GS 2002 Single Spark, which I've owned for a couple of years, seems to be running well (touch wood!) but I'm mulling over possible issues / mods / improvements as follows...

    I'm getting 55MPG with what I think is normal riding: 75-80 on motorways and 50-65 on A/B roads. I'm not unhappy with the consumption but I've noticed that the (standard) exhausts look a bit sooty- if I run my finger inside it's definitely black (but not wet). Is this normal and if not, what can be done about it?

    After losing my rear duck's arse hatch last year I bought a replacement but so far haven't fitted it because it looks as if it might go AWOL again. The two sections of the duck's arse (or whatever we should call it) don't fit together properly in spite of having the little cross-piece add-on fitted. Is there any solution to this or should I just make a lanyard for the hatch?

    Checking the oil level is almost impossible, because even with a bright torch I can't see the through the sight glass! I'm sure this was an accepted issue because the twin-spark oil cap has an integral dipstick - would one be a direct replacement or should I modify my oil cap and add a dipstick?

    My mate JayDee1942 (see his recent thread on solving his twin-spark's refusal to rev over 4000rpm) has opened out the tiny coolant level peephole in the cladding with a dremel so he can actually see the coolant level. That's rather a clever mod as I've been removing the cladding to do this but I still have to remove the cladding to check the battery acid level, which is a complete PITA. Does using a sealed battery mean this laborious chore becomes unneccesary?

    The hand protectors are riveted to metal bracket which clamp round the bars. Is it a difficult job to drill out these rivets so I can get the brackets blasted and painted and then refasten them with nuts and bolts?

    I had a problem with the a chain tensioning bolt working loose which resulted in the plate through which it runs in the rear of the swinging arm being destroyed and from what I have read this is quite common. What's the best method of prevention - loctite or using nylock nuts?

    Is there any function to the "possum scraper" addition to the chainguard or is it just a styling affection which can be discarded?

    The headlight - what headlight? I have bought a pair of LED halo/spotlights and I am debating how to mount them. I know that there is a bracket which bolts under the top yoke which enables you to mount running lights but are there any drawings or dimensions available?

    This bike has only done 17k so I'm keeping my eye on the water pump and the rear suspension linkage but I don't think there's any need to be particularly concerned yet, but any other tips would be gratefully received!

    Thanks in advance!

  2. #2
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    I can only comment on some of the issues.

    55 mpg does seem a bit low for an F650GS but it depends on how hard you ride it. If you are worried about the engine running a bit rich, I would check the state of the spark plug after a long run - the electrodes should be a light brown in colour. Black sooty deposits would indicate a rich mixture.

    I found it almost impossible to check the coolant level on my F650GS using the sight glass - I wouldn't be surprised if the earlier oil level sight glass was similarly useless. If I had the earlier F650GS and couldn't use the oil level sight glass, I would probably have just knocked up a suitable dipstick (calibrate against sight glass level) to poke through the filler cap - it's not as though you have to check the oil level very often. Alternatively, it looks as though the later filler cap with built in dipstick will fit.

    Modern Gel batteries are maintenance free and don't need to be checked - in fact, there's nothing to check!

    I replaced my water pump at ~10k miles purely as a preventative measure so I didn't find myself constantly worrying about it. The problem is that the outer water seal relies on the grease between the two seals to lubricate it and there's no way of easily checking this grease or replacing it. After 14 years, I was doubtful that the grease was still in good condition and so replacing the pump removed all this doubt. That said, having to take off the clutch cover to remove the water pump impellor was a complete pain.

    I took the rear suspension bearings apart to check them after I got the bike and they were all in very good condition. However, the same couldn't be said for the swinging arm bearings. Water had got into one of them and it had seized up. I would therefore recommend doing the same checks on yours but replacing the seals at the same time (basically made out of felt if I remember correctly and relatively cheap).
    2006 F650GS in Black
    9,300 Miles

  3. #3
    Bike
    F650GS 2001
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    Thanks for the reply.

    Initially I thought that 55MPG was a bit thirstly but then I rationalised that JayDee1942's twin-spark does 65MPG so this was the the downside of the less efficient burning of a single-spark. I shall try using a less vigorous wrist action and see what happens, and indeed, a plug chop might be a good idea. However, if it is running rich I'm a bit confused about what can be done to lean it out.

    The current battery doesn't seem to have been damaged by the two full discharges it suffered due to the relay problem a few months ago but when it finally expires I'll fit a sealed battery. I currently have a makeshift dipstick hanging on the garage wall for periodic oil checks but when I fit the new battery I'll open out the coolant sight port and also adapt the filler cap to include a dipstick. That, coupled with an external electrical socket will allow charging through an Optimiser or using a photovoltaic panel should mean removing the plastic just for services to get at the air filter etc.

    The water pump is behaving at the moment but I've got my eyes on it and plan to replace it next winter. There's no play in the swinging arm bearings either but I've got replacement parts ready if it deteriorates, and these include rubber seals, not felt ones.

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  5. #4
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    GS/Gd Dakar 2003
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    Agree with suggestions already posted, look at preventative check on suspension/ SWinging arm not just bearings, but seals too, as these deteriorate , let in water, not well greased from manufacture =wear like SHB

    Re seeming rich mixture look at air filter, clogged? Dirty, collapsed? especially if never replaced with your low mileage, bit of a bugger to get too
    MPG on borderline of low for this model, depends how you ride, hilly area etc, check rear brake not binding , well known fault, rubber cover on brake slave cylinder deteriorates, lets in water, piston sticks, I know from experience . Ok when set off, but didn't release fully during rides, eventually had to prise pads open to get home
    hand protectors - drilling rivets out and replacing with bolts doable, take it easy so drill doesn't slip, replace with rivets if got rivet gun, or nylock nuts and/or Spring washers with bolts as belt n braces job, h/ bars vibration .. .. . . .
    suggest same with chain adjuster, loctite works ok, but remember it's an adjuster
    2003 GS Dakar
    BMW Panniers, top box, tank bag
    + loads TT stuff that came with it!

  6. #5
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    F650GS 2001
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    Thanks, I recently checked the air filter when I had the bike apart to sort out the load relief relay problem - it had been recently renewed. However, even if the air filter were partially restricted shouldn't the fuel injection system balance the fuel mixture and the result would be decreased performance rather then a rich mixture? I live in south lincolnshire so hills are few and far between and I have no brake binding problems although I'm aware of the possibilities of getting them.

    WRT the handgrips, as long as there are no gotchas with removing the rivets, and although I've got a rivet gun, I think the hand protectors will look better with stainless torx screws with nylocks underneath rather than rivets!

    When threadlocking the chain adjusters you have to take the bolts right out, treat them and then wind them back every time they are used. I read somewhere that nylocks were not a good idea although I don't understand why; perhaps aerotite nuts could be used?

  7. #6
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    What a motorcycle fuel injection engine relies on is the O2 sensor in the exhaust to tell it whether the fuel-air mixture is correct. In principle, if this is not working correctly then you could end up with a rich (or a lean) mixture. I would do a spark plug colour test first to try to establish whether there is a problem or not.

    Nyloc nuts are reusable and would be fine for this application especially as all you want it to do is to stop the adjuster bolt from unscrewing.
    2006 F650GS in Black
    9,300 Miles

  8. #7
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    'Morning AWJDT,

    JayDee and I came to the conclusion yesterday that after a plug check the first quick-and-dirty (cheap-and-easy) test should be the O2/lambda sensor change - on offer for £20 on Ebay, with a 2-year warranty. Has anybody got any experience on using unbadged lambda sensors?

    After reading up on them it appears that the major difference between many is just the electrical plug rather then the sensor itself!

    Regarding the chain tensioners, I concur with you - lock nuts it is then!

  9. #8
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    To keep everything in perspective, I've just had a look at the average mpg figures reported for different model years for the F650GS. For 2002, the figure was 50 mpg compared with 60 mpg for my 2006 model. On this basis, your 2002 model petrol consumption looks pretty good compared with the average for that year! At 55 mpg, that's still a range on a full tank of petrol of over 200 miles which isn't too bad.
    2006 F650GS in Black
    9,300 Miles

  10. #9
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    Thank you AWJDT, my mind rests a bit more easy!

    Could you tell me where you find these figures please?

  11. #10
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    As you were thanks, scratch that - easy enought to find!

    However, when I switched the fuel units from US gallons to UK gallons the average consumption is as follows:

    2002: 63.4mpg
    2006: 69.8 mpg

    This doesn't tell such a rosy story...
    Last edited by Andy.I; 10-05-2020 at 08:52 AM.


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