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  1. #1

    Electrical needed

    Got my '93 sl650 to the water after a rebuild and new paint etc and had a BAD day. Wouldn't run for beans. Finally realized that only the center cylinder is firing. Compression good on all 3 cylinders. Both Mag and PTO cylinders wet with oil/gas mixture, but a very light spark on all wires. Loaded it back on trailer and came home. Since I do it all by myself, I even banged the heck out of my shin getting it back on the trailer since the ramp was kinda crowded and I was trying to hurry!

    Anyway, came home and went thru my book and read the forums. Started with checking the coils. It says check the ohm meter for the "offset", which in my case was .2. Then I check each bk-wht to black on the each coil (with the wires separated) and pto reads .3, center .4 and mag .3. It's suppose to be .6 on each. Subtracting the offset, I say they are .1, .2 and .1 It say all 3 in series should be 1.8, I get .6 for all 3 in series! The reading from the coil blk wire to the end of the plug wires were all 3,300 as they should be (with the caps removed) and all 3 were correct from the black wire to the inside of the actual plug connector 8000-9000

    Now, the center cyl was firing and it would idle, poorly, on just the center, but that's it Can the center fire with just a .1 ohm increase from the others?

    Are ALL the coils bad, or am I doing something wrong....any ideas???????

    I haven't done the exciter reading, etc, yet!

  2. #2
    Click avatar for tech links/info K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Can you recheck those primary ignition coil readings with a different meter? Possibly a better grade meter?

    Not saying your meter is wrong, just looking for confirming data.

  3. #3
    I'll get a new one tomorrow! It's a cheapo! I will post new results tomorrow night! Have to be gone all day! thanx

  4. #4
    Join Date
    Jul 2007
    Cedar Rapids,Iowa
    Did you run the ski before the rebuild? If it had good spark then, I would check all your connections and grounds. Is were the grounds connected clear of your nrw paint. Very unlikely two coils would just go bad. How good is your battery.

  5. #5
    It had been mothballed for 7 years because I cooked the PTO! I will check ground reading! And, yes, I was thinking that 2 coils going bad was kinda strange! I'll get right back re: ground reading before I have to leave for the day!

  6. #6
    Did some fast checks on continuity/grounds. Readings from the lower jug nuts range from .2 to 1.0 From the piston tops to the main base plate ground read .1 From the Head nuts to base plate ground are real about .7 - 15.0 The safety switch is ok! I get the same readings from the internal Elect Box grounds to the various spots. The readings from the head bolts to the jug bolts are anywhere from open to 146.5 to 80.0

  7. #7's a new wrinkle. I said that the compression was good...but....I just rebuilt the engine. It has new rings, one new piston and all cylinders were honed. It has not run more than 3 minutes since putting it back in. I checked the compression and center is 90, pto is 60 and mag is 60. don't know how that can be unless they haven't had time to seat, obviously?????????

  8. #8
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Medina, Ohio, United States
    If you rebuilt the motor, put the correct size pistons and rings in, all gaskets are in place, and everything is torqued as it should be, your compression readings should be in the 120 +/- range, regardless of break in. Something is wrong.

  9. #9 me stupid! I just said screw it and ripped the top end off! Lo and behold, I didn't check the ring gap and they sent the wrong ones....and stupid me put them in and forgot to check the ring gap! Book says .008-.018" THE SMALLEST RING GAP OF THE 3 CYLINDERS .145" Hello, call me ignorant and stupid! Pretty hard to get a decent compression with that! One of the old rings that I took off the center cylinder measures .024 in all 3 cylinders! I replaced those with ones that I was lucky to get 60 psi! Did I say call me stupid? I did a 2 day Fed X. I'll report back when I fix this blunder!

    By the way, even though I had run it (center cylinder firing only) after I put it in the water to try and tune it (before I realized the compression was screwed) when I took off the heads, the cylinder water ports were full to the brim with water? Shouldn't that have been blown out?

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