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Intermittent Engine Running Problems


d3ac0n

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The problem is intermittent. She runs good, sometimes for hours at a time, then the problem that occurs is misfiring out of left cylinder, hesitation, bog then ultimately the motor dies. When this happens, it's a HUGE struggle to get it to start back up. Sometimes impossible.

From what I've noticed, the only correlation to this problem is alot of throttle, anywhere from 3/4 to full throttle. But it is intermittent. that doesn't always cause it. I've been struggling with this problem of its runs good then it turns to complete crap ever since I bought her about a year ago. I've tried a lot to no avail. I really hope someone can help me.  Thank you so much in advance for all who may decide to chime in!

I'll explain all that I've done

- Replaced cracked intake boots with new ones (no cross over tube)

- Replaced stock reeds to vForce4's

- Performed leak down test, it was leaking through intake gaskets, yamabonded them, re-checked, no more leaks, motor held pressure

- Compression check Left cylinder = 125 psi , Right cylinder = 130 psi

- Cleaned 35mm pwk Keihin carburetors, ensured 16mm float, went down 1 size in main and pilot since it was running rich. Now @ 158 main & 45 pilot ( I ride at 2,000ft above sea level ) They are on the middle clip position. I've tried 2nd from the top (above middle) this made the problem happen real quick.  I've tried 4th from the top (below middle) couldn't get it to idle. My air screw mixture screws are at 1 & 1/2.

- Made sure to properly synchronize the carbs with snail meter

-Replaced ignition coil (spark plugs weren't always sparking with the original) thought that was my problem. New ignition coil provided proper good spark but didn't fix the problem

-Checked flywheel for rust and pickup coil gap, everything was good. I'm @ 4 degrees advance.

-Checked wiring harness for hot spots or melting. It looked good.

-Re-packed the exhausts with new packing

TORS was removed by previous owner

NOW please don't make me feel worse than I already do for this HUGE mistake I made, it still painfully troubles me today, I sold the original yamaha cdi box because I didn't think I needed it. I got a high output 200w stator  + voltage regulator/rectifier + a "high performance cdi box" from RaceTech Electric to better power my LED lightbar. Thinking this new "high performance cdi box" would outperform my old original yamaha cdi box I sold it like a fool.  I am worried maybe my problem is due to the CDI box since I bought a cheap $10 one off amazon and connected it.  The amazon CDI box instantly mimicked the problems I randomly encounter, only difference is, the problem wouldn't go away and it ran even worse than usual.

When she acts up, the Left exhaust pressure is very weak in comparison to the right exhaust.  I'll put my hand over it to feel the difference. Also there won't be smoke coming out of the Left exhaust for a few seconds then suddenly it'll spit out more smoke than the right.  Very weird because when it runs good none of this happens. Both exhausts push out equal pressure and equal smoke. Possibly this is due to the Left cylinder compression being 5psi below the right? Left = 125psi , Right = 130 psi

Anyways, I'm leaning towards bad cdi box, faulty/shorted wiring harness, or a full on rebuild at this point but I'm new to banshees and not sure if there's anything I've overlooked or anything else I should inspect.

All input and feedback welcome. I'm open to any and all advice at this point. I'm willing to do just about anything for a fully successful riding trip with my new baby

 

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  • 4 weeks later...
  • 4 weeks later...

The problem has been fixed! 97Screamer was correct. Although I cannot tell you which electronic was the main culprit, what I can tell you is the ignition coil on it WAS NOT OEM yamaha, I replaced it with a brand new yamaha OEM one. Replaced race tech electric stator with brand new OEM yamaha stator. Replaced race tech electric cdi box with a used OEM yamaha cdi. Problem solved. Runs better than ever!

To all who read this, learn from my mistake, dont chance it with cheap aftermarket electronics on banshees, totally not worth the headaches!

Edited by d3ac0n
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