Dakar Dazed II - the return! Part 1: Project LC4-50

Discussion in 'Racing' started by JMo (& piglet), Jan 26, 2013.

  1. Sparrowhawk

    Sparrowhawk Long timer

    Joined:
    Sep 26, 2005
    Oddometer:
    3,008
    Location:
    Eastern Washington, USA
    In some circumstances you could but not likely with this engine. With the smaller stroke you need to run the top of piston a little higher at TDC to maintain the same compression ratio. (You are only squishing 450 cc into the space above the piston where you used to squish 650 cc.) That makes it closer to the lower end of the valves when they are open (the end of the exhaust stroke). You need to reshape the top of the piston to prevent contact with the valves and there could also be issues with ring placement depending on the particular engine cylinder/head design. The nice thing then is you have a piston that could be placed in the standard stroke engine that would raise the compression ratio over stock. Cool idea.
  2. JMo (& piglet)

    JMo (& piglet) Gone a bit Baja

    Joined:
    Apr 1, 2007
    Oddometer:
    5,926
    Location:
    Somewhere west of Laramie...
    Top explanation there Sparrowhawk! - I don't think either John or myself could have said it any better!

    As you say, to raise the compression ratio back to where we would need it for reasonably decent performance, the piston in effect needs to move a little closer to the top of the cylinder/combustion chamber... we are hoping that by essentially doming the top/centre of the piston, it will create the necessary compression, while still allowing clearance for the valves, and at the same time not buggering up the whole efficiency of the chamber itself... (suck squeeze bang blow).

    The only other thing I would add to give Greg (or anyone else) a clearer picture of the mechanics of the conversion is that in using a longer rod with a shorter stroke but in the original cylinder/barrel - we are effectively no longer using the lower part of the cylinder wall that was swept with the stock crank and rod...

    Hopefully that clears up any confusion!

    Jx
  3. greglewis

    greglewis Adventurer

    Joined:
    Sep 5, 2011
    Oddometer:
    68
    Location:
    Oak Park, Illinoisistan - the straight road state
    A big Thanks to all of you. Sparrowhawk - I like your idea of drawing a picture - "See Spot run" always worked for me!
    Any idea where I could find some of the engine's measurements - rod length (center-to-center), piston (crown-to center-of-wristpint),crankpin-to-center-of-crankshaft?

    Greg
  4. motorollie

    motorollie Adventurer

    Joined:
    Nov 20, 2012
    Oddometer:
    44
    Nice... looking forward to see how it will perform at the Hellas Rally... see you in Greece!
  5. JMo (& piglet)

    JMo (& piglet) Gone a bit Baja

    Joined:
    Apr 1, 2007
    Oddometer:
    5,926
    Location:
    Somewhere west of Laramie...
    Is that you Ollie? I thought I recognised the photo in your avatar!

    It would make a great Heroes' bike huh?

    Jx
  6. NordieBoy

    NordieBoy Armature speller

    Joined:
    Dec 2, 2006
    Oddometer:
    7,172
    Location:
    Kiwiland
    They were protested against so the ASO had to act.
    It came down to them not bringing proof they were road legal with them. One of their customer quads had his paperwork and was allowed to race.
  7. beasty

    beasty Adventurer

    Joined:
    Feb 5, 2012
    Oddometer:
    27
    I'm probably showing my ignorance here but if you retain the bore of the 690 won't that make the 450 a very short stroke engine?
  8. Hillbilly501

    Hillbilly501 Ultra n00b

    Joined:
    Oct 29, 2010
    Oddometer:
    172
    Location:
    Drinking from the firehose in Brisbane, Australia
    I hope this isn't a silly question, but when you front up to the scrutineers with 690 written on your bike to a 450 race, I'm assuming batting your eyelashes won't cut it and the French don't do 'scouts honour' so how do they go about checking what the displacement of your motor is without actually pulling the whole thing apart and measuring things?
  9. cross-country

    cross-country .

    Joined:
    Aug 2, 2005
    Oddometer:
    1,767
    Location:
    Grand Junction, CO
    In comparison the KTM 350 is 57.5, only 2.5mm longer.
  10. cross-country

    cross-country .

    Joined:
    Aug 2, 2005
    Oddometer:
    1,767
    Location:
    Grand Junction, CO

    I'm guessing by measuring the amount of air displaced by running the motor through.
  11. beasty

    beasty Adventurer

    Joined:
    Feb 5, 2012
    Oddometer:
    27
    A bore of 102mm (690) would require a stroke of 54.9mm to make 449cc
  12. motorollie

    motorollie Adventurer

    Joined:
    Nov 20, 2012
    Oddometer:
    44
    Yep.. my first rally after Heroes Legend 2009 actually :) Was about time...

    It would make a good bike for HL, although you could run the full 690 there. I think it's a good project ... good to see people try something different. The only downside could be the weight. And as mentioned... the French scrutineering ;)
  13. RoninMoto

    RoninMoto Wanderer

    Joined:
    May 12, 2010
    Oddometer:
    1,719
    Location:
    In the mountains?
    Jenny,
    Thanks for posting this on FB.. I might not have found it otherwise. Good luck and I'll be watching from where-ever I am :deal

    John,
    This is all you could talk about when I was there in September. To many sleepless nights thinking about it and you finally had to dig in? So awesome. Keep up the good work. Let me know if you need an ADV test bike :lol3
  14. charapa

    charapa Been here awhile

    Joined:
    Dec 4, 2010
    Oddometer:
    535
    Location:
    Huanuco, Peru, SA, home in Mid-Coast Maine, USA
    Jenny,

    Great project! I don't know how you do it, but these kind of projects really mess me up! I can sleep anywhere and at anytime I choose to, EXCEPT when I have a project like this on my mind! I guess it is the Mechanical Engineer nerd in me coming out! When I get something like this project in my head, I just can't sleep... I end up doing CAD in my head all night. Now... If I could only do CAD in my dreams... then we could get some sleep AND get some things figured out! :evil

    I grew up in the Amazon jungle on a large mission base. Everything was motorcycles for us. We had the run of machine shops, aircraft "clean" rooms and aircraft parts, TIG welders and more. I grew up thinking every 14 year old knew how to run all this stuff! What we DIDN'T have was "off the shelf" parts available. So we made and adapted our own. We would take our Honda XL100s and put Honda 305 dream pistons in them and use carbs off other bikes. Compression was so high we had to run 100/130 aviation fuel! We split our own cranks, repositioned the pins, shortened rods and then balanced them ourselves... Was this NORMAL for a JR High kid??? :lol3

    They sometimes blew up, but it was great fun! :rofl:rofl

    So... I follow with bated breathe this thread. As I now live in Peru (again) and operate a Moto Adventure company, I follow each SA Dakar personally and will be there cheering you on (and lending any technical or logistics support you may need while in Peru!).

    Cheers! :clap :clap :clap Toby
  15. Jurassic

    Jurassic Long timer

    Joined:
    Apr 25, 2008
    Oddometer:
    1,068
    Location:
    Scotland
    What a great post! Nice one Charapa. :thumb
  16. Baja Dad

    Baja Dad Long timer

    Joined:
    Jan 3, 2011
    Oddometer:
    2,396
    Location:
    Norco California
    I have two 690s's a 2011 and a 2008, I would love to do this to my 2008 .
    sounds great-- best of both worlds
    a 690 motor and a 450 motor for one bike !!!!!!!!!!!!!!!
  17. JMo (& piglet)

    JMo (& piglet) Gone a bit Baja

    Joined:
    Apr 1, 2007
    Oddometer:
    5,926
    Location:
    Somewhere west of Laramie...
    Hey Hillbilly! Yes, as cross-country says above, the scrutineers have ways of checking the swept capacity of engines, should they be in any doubt - I imagine this is particularly important with bikes that share similar engines in a different capacity (such as the KTM EXC in 450 & 530 capacities for example). Of course usually the block (which is one of the components marked by the scrutineers) has the cc size cast into it, but that is not to say it might not have been over bored for example...

    We would certainly be up-front about it, and indeed want them to check it, just so there is no doubt in anyone's mind!

    The idea is also to race the event on one engine, without ever having to take it out of the frame, so the original seals are all intact... just to show there is no funny business going on...

    Jx
  18. JMo (& piglet)

    JMo (& piglet) Gone a bit Baja

    Joined:
    Apr 1, 2007
    Oddometer:
    5,926
    Location:
    Somewhere west of Laramie...
    Hi Toby! - thank you for such enthusiasm and support! - we may well be calling on you, if only to find out where to buy beer!

    I do hope we've captured the imagination with the project - and not just because it is 'different' but that the benefits are also clear...

    Not only do we consider this a good way to minimise mechanical issues during an event like the Dakar, but financially it makes a lot of sense [for a privateer] to use a bike/engine combination that isn't going to be scrap, or at the very least need a total engine rebuild after a season of racing (or one Dakar)...

    The 690 chassis is also very stable, and the bike itself generally far more forgiving and comfortable to ride over extended distances - pretty much half the Dakar distance is liaison remember (and technically, more than half, as there were a number of stages this year that had long neutralised sections in the middle).

    Certainly over this summer I will undertaking some long 'endurance' test rides on the bike, not least to see how the fuel-economy is affected by the reduction in engine capacity. The Rally Raid Evo2 Tank kit will mean we have about 22 litres on board, and a lot of the 450s are running as little as 25 litre tanks with, it seems, no real risk of running out?

    Of course this bike will be slightly heavier than a converted WR/CRF/EXC style enduro bike, so where we gain in EFi fuel economy and mapping, we might lose again, especially is soft and sandy terrain...

    But we also have the option of fitting Rally Raid's 5L auxiliary tank to the rear of the bike too, which ought to be more then enough for even the longest Dakar stage, but hopefully we won't actually have to fill that all that often.

    Jx
  19. tehdutchie

    tehdutchie Long timer

    Joined:
    Jun 15, 2009
    Oddometer:
    2,146
    Location:
    Amsterdam or on Twitter @antal
    Why not make life easier, get some 450rr engines and sx-f frames. Standard 24 liter tank and you are sorted..

    At the moment I am wondering if the project is about entering to finish the race, a marketing exercise, an engineering expedition or just a way to drum up funding ( probably a mix of all?) :-)

    All of the above is NOT meant in a negative way :-) so please dont read it as such.
  20. 640 Armageddon

    640 Armageddon Do or Do Not. There is no try.

    Joined:
    Mar 4, 2009
    Oddometer:
    3,567
    Location:
    Greece
    I guess the cost of the 450rr engines is quite high no? Have no idea how much and then you have to add spares etc. The sum quickly goes sky high... :huh And as you suggested ''engines'' (plural :D) so the cost for a privateer is quite high.
    Then, for the 690 engine, because all the internals are kept the same, the head and the gearbox are stock. Already used parts are available so you can have everything cheaper.

    Other than that I feel exactly the same as I think Jenny does for this event. This should be an endurance race for both rider and machine. If they want 'development' they better change the rules and not allow engine changes. :deal Don't get me wrong, but for me, this race was, and still is the ultimate test for rider and machines. I think the downgrade idea :D is very nice as you get a 450 which is overdesigned (because all its parts were for a bigger engine). Neat :freaky

    I think that's it but then again Jenny will come up with a better answer :huh