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The SR500 chronicles - compression

Discussion in 'Technical and Troubleshooting Torque' started by Chairman, May 18, 2005.

  1. Over the past 6 months, I've had opportunties to share my experiences rebuilding the SR500 cafe racer that some will have seen and most will have heard.

    In that time I've:

    - rebuilt a carb by the side of the road,
    - blown out a tyre at freeway speed (and found the inner tube wrapped around the rear hub),
    - fired the exhaust baffles out of the muffler
    - split an external oil line, dropping all the oil onto my leg and the rear wheel as I took a sweeper off the freeway,
    - had a regulator disconnect itself, sending an unregulated 35V to all my 12V globes (flash! - ride home from Flipper's at 2am with no lights)

    and sundry other minor annoyances.

    Today i strolled out to start the bike (after a few days without using it) and kicked it over to TDC (standard SR500 procedure) only to have it rotate past TDC under its own momentum. Hmm...not good. Try again - same thing. Out with the plug, kick it over with a finger in the hole and - no compression!

    So its either a sticky valve or a holed piston. So the motor is out, rocker cover off and over the next few days I'll explore the top end. If it looks a bit shagged, I might put in the 540cc kit and port & polish.

    The long and short of this is that I'm aware that many newer riders won't have seen the inside of a motor, so, if you want to have a look at what's going on inside yours, PM me. I promised to host a spanner day ages ago, but it hasn't happened so for those curious about all the whizzy bits inside your motor, feel free to come and have a squizz.
  2. So when is this exploritory surgery to take place?
    Or is it an on going saga :D
    I'll be in for a perv
  3. Yeah, I'll have to come for a looksee. Must get my bike operational first though.
  4. Yeah, I'd be curious. I need to learn - it was highlighted to me on Monday just how little I understand bikes in general.

    Shame the spanner day never happened - I know I'd still be keen.
  5. hey mark ,
    you forgot the engine bolt fell out as well . :LOL:
  6. Little things, like bolts falling out, electrocuting myself by putting my finger across the capacitor, losing the indicator lens whan it vibrated off, having the main oil line unbolt itself (separate incident to the steel line splitting), breaking spokes, and a small fire when I reconnected two wire arse-about are under the general heading of "sundry other minor annoyances".
  7. That bike's got loads of "character" - surely it can't be Japanese?!!!
  8. Mark, you must really love the bike or wallowing around in oil, grease and muck. If I'd had to do that much to a bike I think it would have been down the the tip...:LOL:
  9. Ever seen - or heard - Mark's SR?

    It's a seriously cool piece of kit. :)
  10. Gromit - no I have never seen Marks SR. I have heard that it's sound is legend and I do like the look of the bikes that I have seen about. In fact I think there was on on Bikesales a few weeks back they wanted just under 5g's for it I think.
    If I had the dough I might seriously considered it. I was just pulling Mark's leg in the fact that he does seem to be underneath the bike a lot (fixing it that is, not falling off it)
  11. I remember reading you can fit engine parts in a SR500 from a Porsche... some thing about valve adjuster?? I'll try and find the web page... But they claimed that the valves were more stable and didn't need to be adjusted so often and the sticky valve problem was eliminated also...
  12. You're quite right - the valve adjusters on a Porche have the same thread as the SR and a larger contact patch so they don't wear as fast. You do need to attack the rocker with an angle grinder to make them fit back into the rocker cover however.
  13. You'll find a photo (including before, after and if-I-win-the-Lotto) at http://www.acevic.org.au/MarksJunk/SRstuff.html. Sadly I don't have a .wav of the exhaust note, but if anyone wants to help me record it, I'd be very grateful.
  14. Forget the .wav file. Just start it up, he'll hear it (wherever he is)! :LOL:
  15. I have a decent mike and the means to record... I'm happy to do the job.
  16. how the hell did you manage to kick the thing over with your thumb over the plug hole!!!!!

    you must be a contortionist!!!
  17. So here's an update. The problem was the exhaust valve. Once the head was off, I did the standard test - fill the exhaust port with petrol and sure enough, I was suddenly standing in a pool of fuel. Inlet was leaking a little also. Cylinder bore has a little scuffing on the inlet side, but the hone marks are still visible from when the head was rebuilt about 10k ago.

    Out with the lapping paste, polish the valve stems and lap the seats and the valves are back in the head. Reassembly will be on Saturday, as I need to machine a blanking plug for the completely useless inspection port that is supposed to tell you when you're at top dead centre. Why is it useless? Because TDC is self evident. On an SR500, TDC is where you can stand on the kickstarter and it won't move. If it does move, TDC was the spot just before your ankle broke.

    And, it wouldn't be a true bodge-repair without something going wrong. Of course, it was an old favorite - I dropped something down the camchain tunnel. Just a plastic cable tie - it probably would have been pulped and caught by the oil filter, but I hate being defeated by this stuff. So, after a bit of thinking, I made a "dropped cable tie extraction tool" (special part #500) and in a trice it was out of the crankcase and on the garage floor. Whew!