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Lucas rita ignition problem?

Discussion in 'Norton Commando Motorcycles (Classic)' started by Pete Komarek, Mar 28, 2019.

  1. Pete Komarek

    Pete Komarek

    Joined:
    Sep 8, 2018
    In a previous post i talked about low end bogging on a rebuilt MKIII. The bogging is severe enough you must rev to 4000+ to take off. The bike will idle but pops intermittently. It acts like a lean bog BUT
    -carbs are clean, brand new. 19 pilot, 260 mains, 106 needle, 3.5 slides. I checked for swarf, all clean. Bike had same problem with old carbs

    - Cams were fine when I rebuilt the top end.
    -Installed as new cam chain-went by specs
    -Appeared on the right side so ignition or carb, I have good spark.
    -Left side black plug from idling, right side black to brown.
    -With choke it runs pretty good, w/o choke boggy.
    -Advanced the ignition to see if timing was off (strobe timed), no difference
    -Lucas Rita ignition- pulled the cover and checked the clearance of rotor to pickup-.008" one side, .016 other side.
    -Spun the rotor in a lathe, spins concentricly

    Would the difference in clearances cause a poor spark or timing to one side?

    I am stumped
     
  2. dynodave

    dynodave

    Joined:
    May 28, 2003
    Yes it will throw the timing stagger way off. Rita rotor tapers were not made that perfect. You must bias it during assembly to make them exactly the same on both gaps.
     
  3. Pete Komarek

    Pete Komarek

    Joined:
    Sep 8, 2018
    Thanks Dave. Next step.
     
  4. Pete Komarek

    Pete Komarek

    Joined:
    Sep 8, 2018
    So... got a degree wheel and checked the cam timing. It was off. When i installed he cam chain I counted links instead of rollers. Waiting on the cam seal so I can install the rotor and time it properly. The intake cam lobe centerline is at 107. Optimum is 102. Will this make much difference on a stock 850? Will advancing the timing help?
     
  5. dynodave

    dynodave

    Joined:
    May 28, 2003
    Last edited: Apr 5, 2019
  6. Hillbilly Bike

    Hillbilly Bike

    Joined:
    Oct 18, 2018
    Dave, I helped Pete with the cam timing, I race Triumphs so I have done a lot of cam timing, but none on Nortons...We are sure the timing is set on the factory punched marks...So you say let it be at 107 for street use?
     
  7. dynodave

    dynodave

    Joined:
    May 28, 2003
    There is no reason to tweek a normal stock cam. You should make a normal 42-45 RWHP if tuned well. If it is a stock cam then it should run fine. If it doesn't then you do have another problem.
    Observing the crank and intermediate gear marking/placement is the most often mistaken and hardest to identify and see.
    The cam gear marker is 12 deg CCW from straight up...Which happens to be the angle/position of the lifters.
    This shows the RH valves in overlap and the LH cylinder on compression.


    [​IMG]
     
    Last edited: Apr 5, 2019
    Pete Komarek likes this.
  8. Pete Komarek

    Pete Komarek

    Joined:
    Sep 8, 2018
    Thanks Dave. By gear mesh do you mean the alignment with the crankshaft pinion? We painted the alignment marks and verified they mesh correctly.
     
  9. Pete Komarek

    Pete Komarek

    Joined:
    Sep 8, 2018
    Yes exactly how we did it this time.
     
  10. Pete Komarek

    Pete Komarek

    Joined:
    Sep 8, 2018
    I appreciate the picture!
     
  11. Pete Komarek

    Pete Komarek

    Joined:
    Sep 8, 2018
    So... Reset the cam timing, re-assembled the ignition. Started her up, sounds great. Quick blast up the road and my new bronze exhaust nut starts spinning off so back to the garage. Hillbilly Biker helped me strobe time it and I took off for a short blast. Wow, nice power, everything working well...*^$*^%#$^%bike dies at 80 mph. Starts up again but dies pretty fast. Now I have to push it up a hill to coast back to my house.
    3 minute ride. Compression test shows 150 lbs left, 90 lbs right, a seizure on one side. Plugs do not have any aluminum on them so hopefully no metal in the bottom end.
    When I disassembled the motor to rebuild,
    the cylinders had a fresh hone and used pistons with new rings already so I just did the valves, etc.

    The Cat Piss Special strikes again
     
  12. acotrel

    acotrel

    Joined:
    Jun 30, 2012
    I always use a degree disc to set the cam timing and strobe the ignition. And you should know when your motor is jetted too lean. If it coughs or goes like buggery, it is probably too lean. Usually you only get seizures when the main jets are too small. If it is too lean at mid throttle, the bike becomes a pig and coughs, as you change up through the gears, when riding it. With my bike, I know immediately if it is too lean, because I am always aware of how it is performing.
     
  13. Pete Komarek

    Pete Komarek

    Joined:
    Sep 8, 2018
    Plug color looked fine. 260 mains. I've seized two strokes before but never a four stroke.
    The acceleration was excellent going up through the gears. No coughing, hesitation, no warning. Then again this was my first ride with correct cam timing. Never rode it before the rebuild.
     
  14. Hillbilly Bike

    Hillbilly Bike

    Joined:
    Oct 18, 2018
    I was there with Pete, a degree wheel was used to check cam timing.. The ignition total advance strobed at 28 degrees at 6000 rpm... it was checked by both of us...The spark plugs showed no signs of detonation....I suspect it was a tight piston fit done by the previous owner...
     

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