Airhead racer rebuild

Discussion in 'Airheads' started by pommie john, May 20, 2008.

  1. pommie john

    pommie john Long timer

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    Well it's been on the track for more than a few years and it's time for a rebuild and upgrade.
    It used to look like this
    <a href="http://s5.photobucket.com/albums/y178/pommiejohn/?action=view&current=ecreek01.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y178/pommiejohn/ecreek01.jpg" border="0" alt="Photobucket"></a>

    Now it's all over the garage floor.
    I've braced the frame at the rear to stiffen up the rear loops in the hope it will help that hinged in the middle feeling when powering out of corners.
    <a href="http://s5.photobucket.com/albums/y178/pommiejohn/?action=view&current=frame2.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y178/pommiejohn/frame2.jpg" border="0" alt="Photobucket"></a>



    <a href="http://s5.photobucket.com/albums/y178/pommiejohn/?action=view&current=frame1.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y178/pommiejohn/frame1.jpg" border="0" alt="Photobucket"></a>

    The side braces have been there all along, but the triangle at the rear is the new bit.
    As soon as it's back on the track, I'l report back on the handling.

    The engine is braced to the top tube.
    <a href="http://s5.photobucket.com/albums/y178/pommiejohn/?action=view&current=brace.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y178/pommiejohn/brace.jpg" border="0" alt="Photobucket"></a>

    And is raised about an inch.
    <a href="http://s5.photobucket.com/albums/y178/pommiejohn/?action=view&current=chassis.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y178/pommiejohn/chassis.jpg" border="0" alt="Photobucket"></a>
    #1
  2. Bigger Al

    Bigger Al Still a stupid tire guy

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    Jeebus, that's pretty!!:clap


    Crap, now I miss racing even more than I did yesterday............
    #2
  3. Nick Makwell

    Nick Makwell Bavarian Murder Weapon

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    That looks fantastic John - what sort of horsepower is your bike putting out?

    I doubt an R65 would need that sort of bracing (40rwhp?) Can you explain how you did it?

    Also, what class are you racing in? Post Classic after 1973?

    Pictures are good!
    #3
  4. P B G

    P B G Long timer

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    Who manufactured that fairing.

    I have an S on my bike now, and would love to go to a non-bar mounted, similar to that.
    #4
  5. Stagehand

    Stagehand Imperfectionist

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    QuickQuestions:

    If you raised it an inch, how does that affect the driveline matchup? (trans/shaft/swingarm) and also how does it affect getting to your oil filter? :ear

    it looks like the front cover had a little surgery as well-- like to see details of that.
    its a fine bad ass looking bike, thats for sure :D
    #5
  6. Uncle Ernie

    Uncle Ernie Long timer

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    I was wondering that, too. I'm also wonding WHY he raised the engine? How would that affect the handling and feel?

    Maybe there's no need for an oil filter for racing if he changes the oil at the end of each day?
    #6
  7. kixtand

    kixtand Long timer

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    I can't speak in this case, but all of the other folks I've talked to either have to drop the front of engine of they make that part of the frame removable.
    #7
  8. kixtand

    kixtand Long timer

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    Raising the engine gives you more cornering clearance. A lot of folks will also move the engine forward a bit in addition to raising it to give you more weight on the front end (although it does not look like that was done in this case.)
    #8
  9. pommie john

    pommie john Long timer

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    Morning all. Thanks for your kind comments.
    Time to answer a few questions

    In race trim it puts out 88bhp at the rear wheel. the most we saw on the dyno was 92, but that needed velocity stacks that were so long I couldn't get my feet on the footrests.
    Many people don't believe the figures, but I can dig out the dyno charts if necessary.
    I race it in Post Classic pre1972. It started life as an R75/5 so that makes it eligible even though it has been bored to 1000cc.
    I do have to use an early crankcase which had problems with crankcase breathing when two 500cc pistons were flying up and down at 8500rpm, but some mods fixed that.
    #9
  10. pommie john

    pommie john Long timer

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    The place that raised the engine have a jig that rotates about the swing arm pivot to ensure the transmission lines up still. So when i say the engine was raised an inch, I really meant the front was raised an inch and the back a bit less.
    As for the oil filter, I have to take out the engine mounting bolts, remove the exhausts and drop the engine a bit to get at the filter. I just put a jack under the sump. No one said race prep had to be easy!

    I have a custom made slimline oil cooler take-off plate .
    <a href="http://s5.photobucket.com/albums/y178/pommiejohn/?action=view&current=adapter-1.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y178/pommiejohn/adapter-1.jpg" border="0" alt="Photobucket"></a>

    I've machined a load of stuff from the front timing cover. The more observant amongst you will have noticed it's a late model timing cover, the fins on the side give it away. If anyone complains that it's not in the correct period, I'll fill between the fins with devcon. The later cover is necessary so I can use a Boyer ignition.
    <a href="http://s5.photobucket.com/albums/y178/pommiejohn/?action=view&current=front.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y178/pommiejohn/front.jpg" border="0" alt="Photobucket"></a>
    #10
  11. pommie john

    pommie john Long timer

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    Kixstand is correct about the reason for raising the engine. Cornering clearance. I did try it with the engine in the normal position and it definately turned into corners better, but I kept hitting the rocker covers on the ground so we had to raise it.
    I later got hold of some Mahle race pistons which are 16mm shorter than standard ones. You then machine 16mm of the cylinders and end up with an engine that is 32mm narrower. I never have clearance problems now, and could probably go back to the original engine position if I could be bothered.

    Mahle piston
    <a href="http://s5.photobucket.com/albums/y178/pommiejohn/?action=view&current=piston.jpg" target="_blank"><img src="http://i5.photobucket.com/albums/y178/pommiejohn/piston.jpg" border="0" alt="Photobucket"></a>
    #11
  12. pommie john

    pommie john Long timer

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    It's a Ducati 900SS replica fairing. I can't remember where I got it but plenty of places make them.
    #12
  13. PaulRS

    PaulRS Dutch fool

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    Hi.

    I like what you're doing:clap

    But what about the rear frame? You still use the bolt-on rear?

    I've seen a plenty of old-skool racers fitting an X-shaped re-inforcement between the main frame and the top of the shock mounts.

    Paul.
    #13
  14. pommie john

    pommie john Long timer

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    It is a bolt on subframe, but it's been modified to take a P&M seat which is a bit narrower. It's also been lowered to take into account my ,err, Pedrosa sized legs.
    I'd be very interested to see what others have done to beef up the subframe.
    #14
  15. Nick Makwell

    Nick Makwell Bavarian Murder Weapon

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    Thanks for the replies - I can understand the bracing now, 88rwhp!! Holy hell.

    My R1100S probably didnt put that out!

    Friend of mine when I was a postie raced Nortons in PCRA (pre-72).
    #15
  16. kixtand

    kixtand Long timer

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    Many thanks for the replies and insight. I am in the process of putting together a /5 race bike myself, so anything you can share is much appreciated.

    What size valves and carbs are you running?

    Thanks again--

    kix
    #16
  17. Stagehand

    Stagehand Imperfectionist

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    Sorry for the possibly stupid questions, but do you shorten the head studs, pushrods, and conrods, as well?

    Does it change the angle of the pushrods?

    I guess I am curious about your compression ratio

    Do you run with a starter?
    OR Is it a total loss electrical?
    #17
  18. Alfons

    Alfons Been here awhile

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    Congratulations, pommie john!

    may I humbly ask which exhaust system you are running? To me that looks like Supertrapp silencers. If so, which type is that?

    greetings from Germany

    Alfons
    #18
  19. pommie john

    pommie john Long timer

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    Not stupid questions at all. We shorten the studs and pushrods but not the conrods.

    Yes it does change the angle of the pushrods so the pushrod tubes have to be bent a little to make them line up with the cam follower tunnels.
    The changed angle of the pushrods is a problem because they are not pushing in a straight line they seem to flex. I am thinking of getting some seibenrock pushrods to try.

    Compression is not too radical at about 10.5:1
    #19
  20. pommie john

    pommie john Long timer

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    You're right they are Supertrapp. The downpipes were made specially for me, but the supertrapps are just the normal ones with a racing outlet. They are about 480mm long if that helps.
    #20