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Malfunctioning F800GS

Discussion in 'Parallel Universe' started by MotoLara, Jan 10, 2011.

  1. Steveman

    Steveman Been here awhile

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    Not very much really. I am talking about what is practicable or lets say reasonable. Considering what one wants to do with his bike. And replacing pistons is imho not what one wants to do for one or two big trips. The reasons for pinging are well known.
    Refering to what you write about how many octane points you can (probably) save with ignition/injection alterations you should also take into account that a knocking sensor would not help more if the mechanical basis (low compression pistons or different combustion chambers) is not designed accordingly.

    Unfortunately my linguistic skills are not good enough to scientifically explain the many reasons how and why pinging happens and -very important and often ignored- that engineers distinguish between various variants of pinging and knocking. Joel said he can even hear it, which I doubt for high rev pinging as this is very often not to hear. However, as you say here

    and here

    you confirm my approach. More or less. I wasn't looking for a high tech solution which could affect future production of the F8. I was talking about a short term solution for exactly "the few" hardcore riders you mention here

    And do not tell me you really believe that BMW would give your "just tick a box and pay more option" even a try. :D

    As said above the sensor alone would not cure the problem, at least a few other changes would be necessary. Midnullarbor describes the problem more detailed and his approach is different than mine. Not simple as I tried but more related to a complete technical change of the whole system to cure the problem for ever. By the way I do agree to his approach as an overall and forever solution for all bikes of a production line.

    Everyone who ever worked in the automotive industry knows that they calculate with less than half a cent and multiply this with the number of bikes to be produced. No way of a simple change here imho.

    For sure the least professional method which however COULD work as many people have proven. But without checking a few parameters like combustion pressure, heat expansion etc. not so easy to do for a series production.

    Steve
  2. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    Thanks Joel ... I've got it now ... Lots still to learn!
  3. JRWooden

    JRWooden Homeless motorcycle vagabond ... and ... loving it

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    Here's the one I saved - this guy has a tool that maybe JOEL doesn't even have ...:lol3
    A shatox meter and a knock engine....

    http://volvospeed.com/Review/misc_performance_volvo_reviews/lucas_octane_booster.html

    "When mixed in a 100:1 ratio of fuel to additive the Lucas Octane Boosted averaged a RON reading of 101.4 and a MON rating of 91.8. Giving Lucas in a concentration of 100:1 an AKI of 96.6 when mixed with 93 pump fuel. With a ratio of 100:1 this make Lucas the most concentrated additive.

    When used an a concentration of 50:1 103.1 RON was achieved with a MON of 93.5 giving it a AKI of 98.4.

    To date Lucas octane booster is the only booster tested that had significant results with only one bottle in the tank. One bottle is enough to make 10 gallons of 96.6 octane out of 93. "

    with octane boosters some of the "confusion" comes in (by the intent of the manufacturer) with the way they claim "2 points" of octane boost.... most folks would think that means 87 octane becomes 89 octane ...
    in the fine print (for some brands) we find what it really means 87 octane becomes 87.2 octane....
  4. Midnullarbor

    Midnullarbor Been here awhile

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    Quite right, Steveman, it is all rather uphill & difficult, and I wouldn't want to hold my breath while waiting for a Bavarian "Engel" [or Angela ?!] to come to the rescue on this issue.

    The home mechanic-extraordinaire could carve an additional head-gasket from something a full 1-mm thick, but then there's the question of reliable leakage-resistance . . . and of course, the problem of optimal electronic tuning . . . etcetera.
    And would the increase in detonation safety margin be significant, without knock-sensor feedback?

    And if you are taking off the head, then you might as well go that one bit further, and take off the barrels as well . . . and the new pistons will still leave much the same problems [as the thick gasket].
    All very discouraging . . . and yet so easy for the factory to offer a cost-effective improvement.
  5. JoelWisman

    JoelWisman Long timer

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    Ok, I posted some of the scientific crap about various forms of knock, what they do, and how they are detected by the some engine management systems.

    Proof reading (something I rarely do) I see I left a couple of important things out.

    Auto or pre-ignition induced by after glow (sometimes called incandescence), or continued combustion as new charge is inducted is FAR worse then spontaneous or compression knock. Heavy knock causes local heat stress, high pressure and powerful shock waves.

    An engine that knocks heavily, repeatedly and fairly continuously breaks the lans off of pistons, peens crank bearings, cracks piston skirts and is generally unpleasant to repair.

    pre or auto ignition when sever does all of the above but also melts the piston and exhaust valves and it does it MUCH quicker then heavy knock.

    Many factors that contribute to knock also contribute to pre-ignition, but the 4 biggest contributors to pre-ignition are 1: running too hot of a spark plug. 2: too lean of an fuel air ratio. 3: the carbon deposits that come from too rich of an air fuel ratio or dogging and babying the engine. 4: a super hot engine from overheating (don't just check the catch tank, it being full doesn't mean a fracking thing) often caused by low coolant level which will lead to insane upper cylinder wall temperatures but NOT show on the temperature gauge till it is catastrophically hot.

    NUFF THEORY, theres a lot more but it's increasingly fringe and complex, some is still debated by scientist for goodness sake!


    I don't know how to teach you to hear it other then to cause it and let you listen. I can cause knock in any F8 at low RPM with the throttle alone up to about 5,000 RPM. Beyond that RPM the F8 doesn't knock unless something is fundamentally wrong with the fuel, combustion chamber or engine management. There are actually a number of youtubes of low RPM knock on F8's posted by people that think it's rod knock or something broken in the engine and are super pissed BMW won't warranty their engines. Oddly dealer techs have either claimed they can't hear it or don't know what it is. I have been tempted to explain to them that it's just mild and brief detonation and that I can make any F8 do the same, especially with the shit gas they are likely running, but i'm thinking they would just piss on me. If others want to help them out, please be my guest.

    I have heard high RPM knock under 2 conditions. Massive carbon build up, usually from dogging and treating the engine "excessively mildly". I love the term "excessively mildly"! I saw it used in an email reply to me from BMW FSE Delpizo, but I digress.

    The other time I heard it was on an engine with heavily plugged fuel injectors AND low coolant (and yes, the catch tank was full)

    Both F8's knocked at redline completely audibly through a helmet at freeway speed. I really don't think you can miss it on THIS engine with stock cans IF you know what to listen for. If you are not experienced in what this kind of engine sounds like while having H/S detonation, or listening for it, of course you would miss it.

    Pre-ignition on the other hand is usually pretty quiet at mid to high RPM. If it has ever occurred on an F8 I rode, I didn't hear it and doubt I have ever experienced it, though if I was going to it would have been on the bike with all the carbon build up.

    Pre-ignition is totally recognizable by one characteristic, when to the level of harmful it will cut the cylinder that is knocking to zero power output or negative output. This may not be obvious on a flat 12 or v8. Can even be hard to notice on a 6, but on a twin, it is unmistakable as the bike will become a dog or if it's intermittent, become hurky jerky.

    There are other things that can cause a loss in power but all should be treated as an emergency on a high performance engine like the F8.


    Now, the PRACTICAL. what to do to control both........

    Crud, one more bit of theory. There is a term that is bandied around frequently in specs and brochures and repeated by many that should know better including me. That term is "compression ratio" and it's a term that is virtually meaningless.

    As an indication of a dimension, or to denote something you changed, it means something, but thats it. Compression ratio has NOTHING to do with knock, power, efficiency, or almost anything else. Hard to believe to those not in the biz, but it's true. Compression ratio is meaningless for predicting anything other then the stroke if you happen to know the bore and piston shape.

    What is meaningful is "mean compression" at a given RPM, and that term is even more telling if you also know "volumetric efficiency at a given RPM.

    Engine A has a CR of 13:1 and at WOT (wide open throttle) at 3,000 RPM a volumetric efficiency of 72%. Ok, heres the math 13*.72=9.36 Now we now the "mean compression is going to be 9.36*ambient absolute atmospheric. at sea level, the atmosphere is about 1 bar so 9.36 bar will be mean compression or 135 psi if you prefer

    Engine B has a CR of 11:1 and at WOT at 3,000 RPM a VE of 93%. 11*.93=10.23. wowzers, all other things being equal engine B with an 11:1 compression ratio is going to knock easier then engine A at 13:1 !!!!!

    But all things are rarely equal and engine design has a BIG effect on knock susceptibility but one thing is certain, CR has nothing to do with it.

    Why is this important? Am I just picking on terminology? NO, though I'm not above that :)

    If your engine knocks and you don't feel like installing a low compression piston, theres another way to easily change mean compression. REDUCE THROTTLE :D

    Thats right, closing that big flap in the throttle body just kills volumetric efficiency cause thats what it is designed to do.

    Using engine B, closing the throttle till you get 50% VE will reduce mean compression, uh, not quite 50% cause we didn't start out at 100%, but a lot, certainly WAY below the mean compression you will ever see knock unless your burning a gas diesel mix (which incidentally will blow the hell out of a KLR as well at high throttle).

    Now heres a big one. closing the throttle at redline 50% will reduce VE and power about 40%. Thats cause there are other pumping losses that will go down involving the valves and exhaust. Closing the throttle 50% at 3,000 RPM won't reduce VE a crap cause a 50% throttle opening will hardly affect the small volume of air the engine is pumping at just 3,000 RPM.

    This is also why the last half of the throttle doesn't do squat at low RPM but has a big effect at high RPM.

    Ok I lied, I need a bath and am heating water on the stove cause my gas main broke between the street and house which isn't pleasant in Missouri in the winter so the truly practical stuff in an hour or so.
  6. Bayner

    Bayner Long timer

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    You could also inject more fuel in an ffort to reduce internal temperatures to the point it eliminates your pinging. I have no idea how much it may take but may be the easiest solution in the long run.
  7. JoelWisman

    JoelWisman Long timer

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    Ok, so heres how the bmw S1000 and K1600's as well as many many cars now do it. They have fly by wire throttles (E-gas) upon knock detection they back off throttle a few degrees, then they close the throttle a little.

    Severly retarding ignition and enriching fuel mix at all is going by the way because of emission requirements. Knock control while preserving emissions is one of the biggest things pushing e-gas onto high performance vehicles.

    Lets take a closer look. The F800 is supposedly 82% VE at 3,000 RPM WOT with 12:1 CR. that means WOT 3,000 RPM =9.84 bar mean compression. Latent heat (look up on wiki) is not our friend here and it's directly related to how much you compress a gas. compress it less by applying less throttle and tendn=ency to know falls off rapidly.

    Next the air heading towards the intake valve picks up heat from the intake manifold. run at a higher RPM and the intake air isn't in contact with the manifold as long and charge air initial heat goes down reducing knock.

    The charge also picks up heat in the combustion chamber while awaiting spark, a lot actually. Increase RPM and the charge waits a shorter duration and charge temperature goes way down.

    Next, for complex reasons, turbulating the charge in the engine promotes a harmogeneus mixture and lowers the chances of knocking. Turbulance is far greater at higher rpm.

    All this and much more I haven't written means when you hear knock or are using suspect fuel, get off the throttle and choose a much higher RPM.

    Asa for afterglow induced pre ignition, it's not common but many things affect it. Make sure your plug is the correct range. If your plug looks pretty white and your going to be pushing hard, choose 1 step cooler plugs. But carbon build up is the biggest cause.

    here are 2 safe ways to remove carbon and one thats quite risky unless you really know what you are doing.

    Way number is to remove your head and gently scrape it out. Way number 2 is the Italian tune-up. Many hopefully don't know this, but when you bring your bike in for excessive pinging, hard starting, jerky throttle and a host of other complaints, the first thing we do is try to ascertain how you tend to ride your bike. If any symptoms point to carbon buildup or just general cobwebs in the motor and we think you run the engine at low rpm's often, heres what happens.

    We wait for you to leave or at least be NOT outside the dealership. Then someone like me gently warms up your engine to normal operating temperature. If the gas is suspect or old we drain it and put new premium in. Next we get on the freeway (out of ear shot) in second gear and scream the hell out of the engine right against redline for 10 miles or so. Does WONDERS for bikes that are ridden excessively mild or dogged at low RPM. I have seen clouds of smoke emitted from the tail pipe and watched that cat turn red as tuns of crap that never should have been there burns off.

    I'm good at hearing knock but I would still NEVER do this with fuel I had any question about and even with the highest octane fuel, couldn't do it if build up was too extreme cause that will cause the mean compression to be too high to ride at high throttle at any RPM.

    So, keeping the throttle too high at too low of an rpm, what else is counter productive for a bike that is going to go around the world and maybe ingest low octane fuel?

    That high flow air filter and fancy high flow exhaust! Have you guessed it? Yep, you increased volumetric efficiency there by raising your mean compression on a bike many would agree already has pretty high mean compression to ride in third world countries. Counterproductive :)

    Barring cetane mixed with your octane (very bad), have some really shit gas causing ping. Run very high rpm at very low throttle and put some foil tape over half of the tail pipe outlet. In other words, RAISE exhaust back pressure. This has the same effect as EGR. With more back pressure not as much of the exhaust is expelled and some more stays in the combustion chamber. Exhaust has already burned so it is inert and dilutes the combustion charge without affecting fuel mixture. This brings combustion temperatures down and hugely reduces knock susceptibility.

    If you have an Akro and pulled out the baffle, you did the opposite and your bike is much more susceptible to knock then when it left the factory. If the baffle is still in, it's about the same back pressure as the factory can, as BMW intended it.

    Really radical and kind of a pain but 100% effective. take your PAPER fuel filter out and soak it in clean water. Poor mans water injection, repeat every other mile. This also increases intake resistance lowering VE and also confusing the injection temporarily and increasing fuel mixture.


    The best solution is for everything on your bike to be running correctly and to use good and high enough octane gas, but barring anything short of cetane in your fuel, you can ride this bike anywhere if your ear is attuned to knock when it starts occurring you do some of the above, most importantly shift, get RPM way up and throttle down.
  8. Steveman

    Steveman Been here awhile

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    Ok, thanks. Thats interesting....

    Mh... looks like this is a serious instrument. Damn, the cheap one costs more than if you let that little twin knock and repair it afterwards :D

    Sounds great to me....

    I have to admit that till now for me "2 points" were 2 points as described and not two tenth(?). Not the serious way of doing it imho.

    Many thanks for bringing some ligt into this....

    Steve
  9. Steveman

    Steveman Been here awhile

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    +1 not much to add from my side except that I really can imagine that an additional head gasket or maybe a tailor made thicker gasket could work fine. Maybe even without other changes or just with a little bit of a good octane booster added. The more I think about it the more I like the idea of having a red lamp saying "its knocking mate do something". Maybe this can be achieved somehow. As soon as you know the problem its a smaller problem...

    And no doubt, I still think that the way you described it is the far better (and of course only professional) approach, but how to convince the Bavarians to change something which only a few riders really do need? :evil

    Steve
  10. Steveman

    Steveman Been here awhile

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    Joel, thats heavy stuff for me as non native speaker, but its very interesting and I think and hope I understood most of it.
    However your explanation of CR and that it has nothing to do with tendency to knock more or less is in my opinion not absolutely correct. you are sure right with mentioning other things than CR alone, combsution chamber construction, air inlet, pinch point, spark plug design and thermal value, cylinder temperature etc. etc.

    In the early 90ies I spent hours and hours on the Dyno and we did serious tuning of Kawasaki and Honda racing engines. Of course only 4 cylinders. We had serious trouble with the Kawa superbike engines due to high rpm knocking. Maybe you can hear it, we could not, at least not on 4 cylinder engines running on the Dyno with 12 to 14000 rpm. But you could feel it and I have idea how I could describe that.

    We have tuned the engines exactly to Kawasaki Kit Engine Specs but Kawasaki was always somehow close-mouthed about deatails not described in the kit manuals. And you know what cured the problems? After a hint from Mr. Rob Muzzy (he owned a Kawa SBK team) he gave me on the phone we replaced the kit spark plugs (40 bucks each in 1993!) with cooler standard plugs and used aircraft fuel with 104 instead 100 octane. No more problems. No knocking, nothing else changed just the fuel. And most interesting, the knocking only occured on engines where we raised compression (at this time 12.5:1 to 12.8:1) as Kawasaki described in their kit engine manual. The standard engine never had this problems. Considering that the kit engines had massive coolers and running with much lower water and oil temperatures the only reason for knocking was the higher CR. I just mention that as you say it plays no role, which imho is not correct. I see high CR's as a major reason why engines knock although they are not overheated and are mechanically healthy....
  11. Midnullarbor

    Midnullarbor Been here awhile

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    Steveman, if I may speak for Joel . . . he was not meaning that the "compression ratio" ("CR") was literally unimportant, but that we must not fall into the trap of thinking that the engine's nominal CR is what applies in all circumstances of engine operation ~ nor can the CR be considered as precisely comparable between different engine models/types [in terms of its effect in compression heating of the fuel mixture].
    Please allow for some looseness of American rhetoric !


    Camshaft timing, engine speed, throttle position, and other factors will affect the actual or "effective" CR (which I am sure you were already fully aware of, in view of your experience with engines).
    And you are right of course, in that for any particular engine [without other changes] an 11:1 CR piston will cause less compression-heating than a 12:1 CR piston.

    As I mentioned in an earlier post . . . I still don't fancy crossing Peru while cruising at 5000 rpm in second gear, at one-eighth throttle !
  12. JoelWisman

    JoelWisman Long timer

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    When you raised the CR, that and VE raised "mean compression". CR has an effect, but it's not particularly useful as a measurement unless comparing apples to apples.

    For instance, changing throttle from 5% to 100% doesn't affect CR in the least. It is a static measurement and unaffected by throttle or anything else that affects VE.

    As to your description of the Kawi, now I understand.

    Terminology isn't 100% standardized but there are between 2 and 4 different names for types of abnormal combustion depending on how you lump things.

    Knock, so named because you hear it audibly knock, is the sudden explosive ignition of end gasses. It is only the explosive ignition of end gasses because that phenomenon doesn't occur until pressure is way high due to combustion being already underway. Knock is what makes pistons look like all the ones I have seen here and with my own eyes on exploded F800 engines.

    What was happening with the Kawi was not audible because it wasn't knock but rather "pre-ignition". The text book cause of pre-ignition (though there are others) is too hot of a plugs after glowing and starting orderly normal combustion at the wrong (too early) time. You can feel it but you can't usually hear it. It can be felt ok usually on a 4 cylinder but is 3x more feel-able on a 2 cylinder.

    This is a good explanation of terminology http://en.wikipedia.org/wiki/Engine_knocking

    In any case, raising the CR increased energy density and therefore specific heat which overheated the standard plug. Textbook preignition.

    Make sense?
  13. roadspirit

    roadspirit souvlaki for breakfast

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    Ok, so it is : Downshift to keep the throttle low and keep the rpm high. Also keeping our exhaust and airfilter stock helps. I don't fancy it either as Midnullarbor said, but at least it is good to know that there is a way to reduce impact.

    The only thing i didn't get, due to english not being my native language, is this:
    what do you mean by that? are you suggesting that we place the air filter back in place while it is wet?

    thanks for all the advice
  14. Steveman

    Steveman Been here awhile

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    I think Joel made a joke. A true water injection system would lower the temperature and increase the power output as with cool air you're able to inject more fuel without letting fuel/air ratio getting t00 rich.

    So if you put in a wet air filter this - as a joke - may raise your power output. A poor mans water injection :D
  15. Steveman

    Steveman Been here awhile

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    Sure, your (and Joels) explanations are most appreciated!

    Ooops, OK my fault as I didn't understand it that way. Apologise. No doubt, CR cant be taken as comparable parameter between different engines, thats a fact.

    :D Honestly, American rhetoric and spelling is easier for me than British. I worked for Chrysler so many US terms are not so uncommon. Unfortunately the last 15 years I did not need my lingual knowledge and if then it was pure British English. But at least most Brits say "Steve you're talinkg fookin American stop that darn slang!" :D

    Yep, I fully agree, thats not great fun....

    Thanks
    Steve
  16. Steveman

    Steveman Been here awhile

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    Not sure if VE is what I think, I guess (!) that it could make sense in this case if its volumetric efficiency. However, I fully agree with the above said!

    100% right


    Additionally it is a problem translating the Austrian/German terms into English as very often the translation is not 100% spot on,

    Exactly as I understand it. Additionally it can be said that it appears never in the last third of the rpm range but most of the time from low to mid revs. We too just call it "knock" or "engine knock", these terms describe and mean what you said above.

    OK, I see you absolutely understood what I tried to describe. Unfortunately what you describe as "pre-ignition" is in our laguage also called "knocking", in fact "high rev knocking". Which is literally and physically wrong. Its not knocking and it makes no audible knocking sound. So pre-ignition is correct but menas something different translated to our language. Whatever, we both now know what we are talking about. This pre-ignition stresses the pistons, bearings, rods etc. and leads to a power loss. I am sensible so I can feel it, even on the Dyno but I can not hear it as in fact it makes less noise than common knocking and additionally the exhaust noise, wind, etc. makes it difficult to hear anything. I believe if you say you can hear it on a twin or single cylinder due to the reasons you mentioned above and the fact that these engines normally dont rev so high.

    I'll read it. Thanks.

    Yes Sir, absolutely!

    Thanks for sharing your knowledge, most appreciated. And thanks to you all for not flaming me because of my lingual deficits :freaky

    Steve
  17. roadspirit

    roadspirit souvlaki for breakfast

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    ok! :)

    Anyway, trying to lower my fears I was thinking, probably there are numerous F8GS out there doing road trips in S.America and in Central Asia, globetrotting in general, going to places that good fuel is hard to find and chances are that you will get crap fuel.

    How many F8GS make it safe? How many break? So far, cases that I know of, are Alberto's and Naomi's here, Raymond Behm's bike (http://behm.lu/blog/en/home/) that also broke down in Peru, and Uli's F8 (http://www.alser-on-tour.de/english) that broke down in Alaska.

    Are there other known stories of broken F8GS on the internet? (other forums, other blogs etc) ??
  18. MoToad

    MoToad Been here awhile

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    You know those expressions 'Back in the day" or "When I was a lad"? Well, bein an old fart, I gotta try one. Back in the day we were proud owners of all kinds of "Beaters". This classification covers all those $200 vehicles we would buy and, seemingly drive for an eternity. I've had and seen friends drive heavy knocking cars, and I mean real lemons, pouring smoke and running on 7, 6, or 3 and all we'd do is add more cheap oil (recycled Nugold here in Canada) and change the plugs. Countless miles put on these pieces of crap. So, what happened? How did technology reach such a state that the smallest mistake can convert your $15000 brand new happy ride into your nail biting worst nightmare.
    This thread has turned into such a detailed philosophy class on high tech mechanics I thought I'd just expand on it a bit.
    God, give me back my good ol Blue Flame (67 Blue Volvo station wagon with telltale smoke.):1drink
  19. JoelWisman

    JoelWisman Long timer

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    That old 140, unless u were a cool kid with an 1800 or ancient even then 544, made 108 HP from 1.8-2.0L of displacement, a tun of Hydrocarbons and ran on leaded gasoline.

    Throw away the catalytic convertor and run leaded gas in the F800 and it will make 85HP from 0.8L and be at zero risk of detonation.

    All the high tech wizzbang makes the F800 sip fuel while making massive power but it is true that it's not as tolerant of putting the wrong stuff in the gas tank.

    Ironically, it's a lack of 1980's technology (knock sensor) that makes the F800 less tolerant of bad fuel then the Volvo B18 and B20 power plants were through sheer inefficient mass.

    P.S. A round the world trip in a B20 powered Volvo will cost you more then a new engine for your F800 at todays fuel prices, and be a whole lot less fun, so modern technology isn't entirely without merit :)
  20. MotoLara

    MotoLara ADV rider wannabe

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    Mark 'Radioman''s F8GS engine went tits-up in Tucson, Arizona. The story here