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Is my bike ok?
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15,255 Posts
Discussion Starter · #1 ·
1980 CB750F

So, I slid this bike down road a few weeks ago and today is the first chance I've had to really take a look at it. I have spark on all four cylinders,so apparently my ignition was unharmed. The ignition cover got ate through during the slide and that area was full of gravel. The tip of the ignition rotor suffered some damage,but it seems to be working as it should. When you go to start the bike it snorts,pops and backfires... perhaps it's off time mechanically? I just can't imagine what could have happened that would have caused that? The thought crossed my mind that when the bike smacked the pavement that it could have caused a cam chain tensioner to break allowing this. I dunno. I'm gonna study up on the FSM,but I'm open to any suggestions as well. Thanks in advance for any advice.

Oh,andI've been having a cold start issue that turned out to be a non-working accel. pump. It pumps fuel like Grant took Richmond when I bench test it, but as soon as it's on the bike it won't squirt. :nuts: One thing at a time I guess...
 

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The Hell You Say!!
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2,956 Posts
I would pull the valve cover and check the cam chain. Did the acel pump break when you laid it down? Hopefully you can get it running man. Post up what you find and I'll help as much as I can.


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lb/hp is what it's about!
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10,448 Posts
Thanks buddy. Time has been scarce. I'll holler back. I need to ride. :(
I know that feeling. One KTM is suddenly running way lean, the starter solenoid went bad on the Duke, the xl350 is spitting and sputtering if I give it any gas, the engine in the GSXR fired right up when it was in the Katana frame but now that it has been transplanted will only run for a couple seconds, and the Triumph is giving me all kinds of fueling problems. Sucks when everything goes bad at once. :letsride: :(

Anyway, I have no idea what it could be but I'll keep a eye on what happens and maybe learn something.
 

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Is my bike ok?
Joined
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15,255 Posts
Discussion Starter · #5 ·
So I figured this out. Kinda strange,but simple once I had some time to look at it.

The tip of my rotor was a little damaged,so it was obvious it had encountered some gravel while it was still spinning. Luckily, the pulse generators were unharmed...somehow.

I set the motor up to check static timing and my rotor was way past 180* out. That shouldn't be possible since the locator dowel on the back of the ignition advancer was still intact.

Static timing should look like this setup on the 1.4 mark:


But instead it looked like this:


Turns out, the rotor tip is not keywayed on to the main shaft of the ignition advancer,rather it's just a press fit. It had gotten spun out of phase on it's shaft. Some careful readjusting with some channel locks and she roared to life. :letsride:
 
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