Need 1985 250R Electrical Help

[newby200x]

I picked up a 1985 250R a few weeks ago and have been battling an issue w/ it ever since I got it. I got it running, but it never would open up, it would just fall flat on its face at WOT. After tweaking w/ the carb w/ no improvements and doing some research, I found that the CDI on it was probably the culprit, due to the fact it was a cheap aftermarket unit and rattled when I shook it. I bought a used OEM CDI off of ebay that claimed it came off of a running machine. I plugged it in and had no spark, plugged the aftermarket one in and had spark...so I returned the OEM unit. Ordered the next OEM CDI, once again guaranteed good working unit, plug it in...no spark. Plug the aftermarket back in..spark??? Do I just have bad luck and received (2) faulty units? Or could there be an issue somewhere that is not letting the OEM CDI work? Is there something that could be frying the CDI's? I plan on going over the entire electrical system, cleaning grounds, and testing for shorts...but I can not figure out why one CDI would work and the other not, other than bad luck of (2) bad ebay buys.

[shortline10]

Are you sure your getting 85 cdi boxes ? I thought 86-89 Atc/trx were different ?
Been a year or so since I messed with a 250r cdi so my memory sucks at times lol .
I have seen the China cdi boxes give great spark but won't let the bike rev enough to go into the power band .

[newby200x]

That's the issue this china CDI is doing. The 85 CDI is a round plug, and the 86 CDI has 2 plugs. I've been getting round plug CDI's.

[shortline10]

Did you try and start it with the used oem cdi ? Or just checking for spark at the plug .
The 250r motor at a slow revolution is hard to see a spark , I usually run a cordless drill on the flywheel with the plug removed when checking for spark .

[newby200x]

I didn't try and start it, just checked for spark at the plug. I'll give it a shot though.

[barnett468]

.
ok, another thing is that some of those chinese cdi's need one or more of the wires removed from the honda plug and reinstalled int a different hole whch sounds like this may be your problem . . i would ask someone that has a honda cdi to look at their plug on their harness and tell you which wire goes in what hole . . if yours does not match, that is the problem and you need to put the remove the incorrect wires and put them in the correct holes.

there is a tiny piece on the side of the wire end that needs to be depressed so it can be removed from the plug.

there is a guy called dr cdi or something that has wiring diagrams that might help if no one posts the info you need quickly.

.

[barnett468]

I didn't try and start it, just checked for spark at the plug. I'll give it a shot though.

when you check for spark, its easiest to see in a shaded area . . the darker the better.

[newby200x]

Found the issue...which sounds stupid, but I wasnt kicking it over hard enough. The chinese cdi shows spark on an easy turn over, but the oem takes a little more oomph. Easy fix, but sure was throwing me for a loop. Thanks for the help

[shortline10]

See their :) easy fix and don't feel stupid , took me a while to figure it out when I first ran into this issue many years ago lol .





Found the issue...which sounds stupid, but I wasnt kicking it over hard enough. The chinese cdi shows spark on an easy turn over, but the oem takes a little more oomph. Easy fix, but sure was throwing me for a loop. Thanks for the help