« previous next »
Pages: [1]   Go Down

Author Topic: Timing marks reversed.  (Read 1871 times)

0 Members and 1 Guest are viewing this topic.

manther

  • Guest
Timing marks reversed.
« on: January 04, 2009, 04:28:56 PM »
Started following my Clymer to set the timing on my '77 cb750. The 1-4 points close when the 2-3 marks come around, and the 2-3 points close when the 1-4 timing mark lines up... Whats up with that?

Thanks -J
Logged

Offline number13

  • Hot Shot
  • ***
  • Posts: 521
  • 1973 CB500, 2002 VT750DC
    • Sound Exchange
Re: Timing marks reversed.
« Reply #1 on: January 04, 2009, 04:32:58 PM »
Is your advance unit on backward?
Logged
Bikes parked out front mean good chicken-fried steak inside.

Offline Steve F

  • I have "some-timer's disease" because I'm an
  • Old Timer
  • ******
  • Posts: 2,929
  • "To Ride Is The Reason, The Destination The Excuse
Re: Timing marks reversed.
« Reply #2 on: January 04, 2009, 05:21:16 PM »
The cam part of the advancer unit seems to be put on 180 degrees out,  Have you had the advance unit apart lately?  The whole advance unit is located to the crankshaft with a pin, so the points cam would be the only likely culprit.
Logged

Offline OldSchool_IsCool

  • Really feeling like an
  • Old Timer
  • ******
  • Posts: 4,350
  • WARNING: Objects in mirror appear to be LOSING!
Re: Timing marks reversed.
« Reply #3 on: January 04, 2009, 05:26:28 PM »
Probably TOO obvious, but the 1.4 points are on the LEFT, 2.3 on the RIGHT.  Blue wire on the 1.4 and yellow on the 2.3.
Logged
Can I have a motorcycle when I get old enough?
If you take care of it.
What do you have to do?
Lot’s of things. You’ve been watching me.
Will you show me all of them?
Sure.
Is it hard?
Not if you have the right attitudes. It’s having the right attitudes that’s hard.

Offline scunny

  • Old Timer
  • ******
  • Posts: 4,618
  • don't call me expert
Re: Timing marks reversed.
« Reply #4 on: January 04, 2009, 05:27:30 PM »
from memory so this could be suspect but the advance unit has a mark on it where you line up the points cam when reassembling
Logged
past-cb100,ts250,cb500,cb500,gs1000,gs650g.phillips traveller
present-CB 650 retro
            VTR1000F3
           XL250S riverbed rocket
           TS250[sold]
           TS185[sold]
           XL125S[sold]
           MT50 (white)
           MT50 (red)[sold]
           KN250/XS400 project
           XR/XL250 bitsa under construction
           SL100[sold]
           XL250R
           pedal(pub bike) leaks oil
my gallery http://gallery.sohc4.net/members/personal/scunny

manther

  • Guest
Re: Timing marks reversed.
« Reply #5 on: January 04, 2009, 05:57:11 PM »
I haven't had this part of the bike apart yet, but i'm at least the third owner. When I set out to adjust the timing, the bike was running. Just had a flat spot after 3800 rpm's. Might not even be a timing issue. Might be a float level issue or others, but wanted to check the timing. If the plate was put on 180 degrees wrong, would it run?
Logged

jsaab2748

  • Guest
Re: Timing marks reversed.
« Reply #6 on: January 04, 2009, 06:24:11 PM »
Shouldn't the 1-4 points just be starting to OPEN when the 1-4 "F timing marks line up? Same with the 2-3 "F" marks?
Logged

Offline OldSchool_IsCool

  • Really feeling like an
  • Old Timer
  • ******
  • Posts: 4,350
  • WARNING: Objects in mirror appear to be LOSING!
Re: Timing marks reversed.
« Reply #7 on: January 04, 2009, 06:27:45 PM »
Quote from: manther on January 04, 2009, 05:57:11 PM
If the plate was put on 180 degrees wrong, would it run?

No, the pistons would be near the bottom of their cylinders, not the top.  

You mention the points CLOSE at the wrong time.  What about OPEN?  If memory serves, the coils generate their spark as the magnetic field collapses in response to current interruption in the primary circuit... which happens with the points OPEN.
Logged
Can I have a motorcycle when I get old enough?
If you take care of it.
What do you have to do?
Lot’s of things. You’ve been watching me.
Will you show me all of them?
Sure.
Is it hard?
Not if you have the right attitudes. It’s having the right attitudes that’s hard.

manther

  • Guest
Re: Timing marks reversed.
« Reply #8 on: January 04, 2009, 06:52:10 PM »
it's been about a week since I tried this. But, I made this "ignition on" test light by clymers specs. It's just a 12 volt light bulb hooked up to to D batteries, with an aligator clip coming off the negative side of the batteries. and an alligator clip coming off of the light bulb hooked to the blue wire on the 1-4 points. Somewhere close to when the 2-4 "F" mark lines up the light lights up. Here's a picture of my test rig.

(from week old memory) The points are touching causing my test circuit to connect and then the light comes on.
« Last Edit: January 04, 2009, 06:54:42 PM by manther »
Logged

manther

  • Guest
Re: Timing marks reversed.
« Reply #9 on: January 04, 2009, 06:56:07 PM »
Also I should add that by now I've loosened those three adjustment screws on the plate, and moved the plate all kinds of different directions, and have no idea where it originally was...  Good times.
Logged

Offline bryanj

  • Really Old Timer ...
  • *******
  • Posts: 14,116
  • CB500 Number 1000036
Re: Timing marks reversed.
« Reply #10 on: January 04, 2009, 08:09:31 PM »
Dont know why you have batteries in ther just get a 12 volt bulb in a holder with a wire to contact and wire to case. Put one wire to spring on 1-4 contacts and other to engine case. with ignition ON (and kill switch!!!) bulb will light up when points open which should be when "F" mark lines up with static mark after setting gap at 14 thou. Then transfer wire to 2-3 sping and repeat with2-3 "F" mark
Logged
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!
Pages: [1]   Go Up
« previous next »