No spark on a honda cr 85

I would first suspect the stator. you need to have an ohm meter and ohm out the stator when it is warm...its possible for the cdi to be bad but not typically when it heats.

A few things,start simple disconnect the kill switch,remove the spark plug cap from the wire,check all your coneections from the stator to the cdi box to the coil.Still no spark your going to need a multi meter to check the stator and coil.If all this checks out to be good then it is your cdi box.A word of caution test these parts before replacing as they are not returnable and could get costly.A good shop could diagnose your problem in hour time.It may be money well spent if you do not understand your bikes ignition system.

may be just a bad wire that goes to plug or electrics--get a clymer repair book for testing procedure

The Voltage From The Stator To The CDI Should Be Around 40 Volts(AC) At Cranking Speed. Be Sure Your Meter Is Set For (AC) Not (DC). The CDI Changes The (AC) Input Voltage To (DC) Output Voltage To The Primary Terminal At The Coil. An Electrical Shock Hazard Exist If Stator Voltage Is Checked With Engine Running. Always Perform This Test At Cranking Speed (R.P.M.) For SAFETY. 120 Volts (AC) Can Be Present With Engine Running.

The stator can be checked by using an ohm meter checking for any shorts to ground. The CCI box needs to be checked using OEM testers or substitute a known good unit for TS.

what comes out of CDI box? if you have it going in it is rectified and more will come out. If not change CDI

has it a cdi unit if so most proberly that allso check u got power coming out of mameto status with a volt meter plate

There may be several things causing this fault (your sure the plug is fine?)

The ignition systems on these bikes are pretty basic. The Stator plate provides power to the CDI unit, which builds up until the pulser tells it to send the power to the coil and produce the spark

1. is there voltage from the stator plate (under flywheel) - you can test with a basic multimeter.

2. is the pulser sending a pulse - also can be tested with basic multimeter

3. is the CDI blown? - swap out to test

4. Is the Coil blown? - can be tested with multimeter

it is also very possible that you may have got a couple of wires mixed up when you switched engines.

stator, CDI or pulser. Probably the CDI. It is a common problem