Pretty new to this forum (6 months) and have been getting great info on how to attack issues on my 83' ATC110. So here is the scoop. I replaced my motor with one that had the upper end rebuilt not too long ago (new valves, piston, rings, etc) as mine had low compression and bad oil leak. Got the motor in and used the carb it came with (was suppose to be new OEM). Had nothing but issues with getting it started, so did a compression check and was getting about 165lbs. Getting spark but would not start. So I swapped out back to my old carb and she fired up on the first pull. Ran great but then soon died. Found out I had a vacuum leak near intake. Solved that issue & she ran great again. Went out to start it a few days later and no deal. This went on for about a week where it would start on first pull & run fine then another time nothing.

So I went about and started troubleshooting. Found out I had either a weak spark or no spark out all. Completely checked the entire electrical system. Coil, CDI, pulse unit, AC gen, wiring connections throughout, kill switch, coil wire, plug, etc. Found out I had a bad coil and bad ignition wire (going to plug). Replaced it with an aftermarket generic coil from Hyperparts (red coil). Installed it and she fired up on first pull. She seemed OK for another week or so then the old spark and no-spark crap started again. Did the whole check again and found my pulse unit & gap were fine (per tests in my Honda shop manual and this forum suggests), AC gen ohm/output tests seemed OK (puts out around 17~19v AC on a few pulls, ohms look good), all connections are clean and no shorts and open circuits in wiring harness, kill switch is good, but the CDI unit doesn't seen to be sending any voltage to the coil if I put a volt meter across the coil and pull the starter (per the schematic there is an output from the CDI that fires a signal voltage to the coil. I get nothing when the bike will not fire.

So I conclude that the CDI, since I don't have the right tester, is bad. I have one coming from Dr ATV (after market are only $25), but here is one final kicker I can't figure out. On the cheapo aftermarket coil, if I check for resistance against the primary and secondary coil, I get nothing (its open circuit) on the secondary coil. WTF?? Its suppose to be brand new so why would I get nothing? Could a bad CDI unit that was intermittent burn out my new coil? Or could I have had a bad coil that cooked my CDI? The Honda book clearly states that you should get resistance on the pri and sec portion of the coil. This is true for all coils aftermarket or not right?

I have also read in another manual that constant trying to start a CDI system in which the bike will not start can overheat the coil and burn it out. Since I have tried to start this SOB many times without it firing leads me to believe I did this. Can anyone offer wisdom, suggestions or direction???

I just bought an aftermarket CDI, a DIFFERENT coil & as back-up..... a stator coil on its way from Dr. ATV. Should I just pull the coil that is suspect, install the new one and the CDI and see what happens (but leave the stator out)? All my tests point to the CDI but the lack of resistance in the secondary portion of the coil baffles me.

One additional info tidbit. I have not checked the valve clearance yet as I assumed that decent compression led me to believe that the valves are OK. I know the spark issues have nothing to do with this but should I check anyway since I am not too familiar with this motor??

Suggestions?? I want to get her on the trails in time for Memorial Day holiday. Please help guy!! She's a nice resto bike I have been working awful hard on (check out my page for pix of the 110)!!

Thanks,
Sam
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UPDATE: So I go to try once again to see if the 110 will fire as its been dead again for about 4 days. I reinstalled the old CDI unit (ignition module) and in one pull she fired up. I let it run for about 15min just to see if it would die and it purred like a kitten.

WTF?!! So I know from reading on this post and talking with my buddy who owns a TRX125 that others have also had this issue. Any ideas?

Can a CDI ignition module go intermittently bad and run for a speall then just go bad? The new one should be in any day now but this just doesn't make sense to me.

Come on now....won't anyone take a stab at this?

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I would look for a wire going to ground
Look for a pinched wire possibly past forks behind headlight or coming out of engine case
Any where wire runs
Even the ignition switch could cause issue
Problem is frustrating being intermitant
Could be as stupid as only does this when handle bar turned right or left
That is why I would look for pinched wire or insulation rubbed off
Thanks
Ray

 

All great suggestions, however I've been down that road and found nothing. What I have found is that the CDI module was indeed my issue. Replacing has solved my woes! The sucker starts on the first pull now every time (except when she is good and hot then it takes maybe three pulls).

Thanks!