Thank you in advanced for helping me with this really frustrating problem !

I just purchased a Honda TRX-125 for my 11 & 13 year old's, and it seem to be fine when I picked it up, but then I discovered that it dies after running about 15 minutes !

Symptoms: Starts immediately. Runs well, good accelleration. After it starts to heat up, starts misfiring, then needs more and more gas to keep running, very little power, finally can't keep running even at mid-throttle, and dies. Wait a couple of minutes, starts-up again fine, then within a few minutes sputters and dies again.

What I have done so far: Replaced battery(new), Pulled carberator and cleaned throughly (3 times), Cleaned and oiled air filter, replaced spark plug, , Replaced Main Fuse Assembly, Valves Adjustments (.003 in.) twice .

Tested so far: All electrical components (Ignition Coil = good, CDI has strange readings on resistance and fails 11 of 30 tests from the Clymer Manual, Voltage Regulator also has some odd measurments, Charging and Exciter coils = good, fully charged new battery). However despite the resistance tests of CDI and VR, always has good spark when I pull plug and test for spark upon engine failing. Performed a Compression Test 160-170psi w/o oil, 175-180 psi w/oil added to cylinder.

Other notable issue: Battery is at full charge (battery tender) when I start up cold. After I start up, the voltage never exceeds battery voltage (12.52v) at any RPM 2000-10000. While running, I measured between where the main fuse goes, and got only a reading of 0.2 amps. While running, I disconnected the battery and measured the ground to hot lead voltage from the vehicle, and got a 0v reading (yet the vehicle is obviously producing power which is being sent to the CDI and ignition coil to keep the machine running (so I know it's not running off the battery). Also the previous owner had just replaced the battery last December ('03), and 3 of the 6 cells were completely fried, which is why I replaced it, but I am thinking the Voltage Regulator is fried too (so I bought another one on eBay).

My assessment is bad Voltage Regulator, but I want to find out if anyone else has experienced a similar issue ?
Is this also a symptom of a bad CDI ?

Has anyone ever tried an aftermarket CDI like www.procomengineering.com sells for either TRX250ex (ATV), or XR/CRF50-230's (Dirt bikes) ? They are cheap ($45) and have a good return policy, especially since Honda discontinued the Shindengen OEM ones.


Any help would be most appreciated.

Sincerely,

John Martoccio
Fox Lake, IL
john at fastad.com (if you put it together)

 

Sounds like you got a good handle on things.
Sometimes stators have two separate windings. One for the ignition and one for charging. Its possible the one for the ignition is opening, when hot.
The charging system should put out close to 14 volts at 4000 rpm.
Next time it dies, immeatitly check for gas in the float bowl. Loosen the screw, on the bottom of the carb and see if gas comes out. If it doesnt, you may have a plugged tank vent, or carb vent.

 

I am fairly new to the atv scene, but does the atv have a filter screen in the fuel tank at the petcock like a motorcycle? If I am reading right, sounds like you always have a spark at the plug. Mis-firing when running out of fuel is common with bikes and autos..Sounds like maybe a fuel problem to me. I will be curious to see what you find. Good luck.

 

Thank you for following up. I wanted to comment on some of the suggestions, and perhaps add some more information to this dilemma.

Thought I found the problem, with one of the two mounting studs on the carburetor stripped (in the body) and was not tightening down and leaving what I was thinking might be a small crack for raw air to be sucked into, but that wasn’t it either. As soon as it starts warming up, it starts to misfire and is starved for air/fuel (even though it seems to be running rich) until eventually, no matter how much throttle I give it, it dies out.

As to the charging problem, since I am not getting any recharging power at the battery, I decided to see if I am getting AC coming off the charging coil. At starter-speeds I am getting 9.8 vAC, but at running speeds I am getting between 26.5 vAC at idle, to over 90volts at highest RPM’s. It’s obvious that the coil is putting out power, so now it is looking more-and-more like electrical issues Voltage Regulator or CDI. I just ordered a V.R. on Thursday (eBay), so I am waiting for the replacement to come-in, install it first and see if there is an improvement, before purchasing a new CDI.

I was speaking with someone else, and was told that the Voltage Regulator failure was unusual with this model. But my first analysis was that the CDI failed 11 of 30 resistance tests and V.R. failed all of the tests (according to Clymer's manual) seems now, pretty accurate. The issue that bothered me was that the Clymer manual also said my ignition coil's secondary winding should be 3.7 to 4.5 ohms resistance, when I believe they meant K Ohms (3700 to 4500), so I was thinking they might have made other mistakes. I have since ordered a PDF of the Honda TRX-125 Manual to be double-sure I don't have any other specification issues.

I have just never seen such a wide range of problems on one vehicle before !

I have also read about another site in another forum here, that pointed me to http://servicehonda.com/test and when I checked them out, I found that they offer better microfiche cross-references to discontinued parts (as I found a CDI for mine) and all the parts at considerably better prices than bikebandit.com or at dealers I had called.

Thanks everyone...
-CPUjohn

 

check your plug to see what color the tip is. u could be running very rich and getting too much gas

 

Sounds electrical. possibly the coil

 

MY 03 RANCHER HAD QUIT CHARGING TOO A WHILE BACK. I WENT TO THE DEALER TO GET A VOLTAGE REGULATOR AND HAD TO ORDER ONE. THEY SAID THEY HARDLY EVER GO BAD. A WEEK LATER IT CAME IN AND I PAID AROUND 80 BUCKS FOR IT AND HAD THE SAME PROBLEM. THE SECOND DAY I STARTED THE RANCHER AGAIN AND WITHE THE VOLT METER HOOKED TO THE BATTERY I STARTED CHASING WIRES AGAIN. BENDING AND TUGGING AT PLUGS AND SO FORTH. GOT ALL THE WAY BACK TO THE REGULATOR PLUG AND SHOOK IT AND IT STARTED CHARGING. I CLEANED THE PLUG AND TIGHTENED THE CLAMPS INSIDE WITH A SMALL SCREWDRIVER. NO PROBLEMS SINCE. I HAVE AN EXTRA BRAND NEW REGULATOR NOW! I HAVE BOUGHT DIRT BIKES CHEAP IN THE PAST BECAUSE THEY SUPPOSIDLY NEEDED NEW CDI BOXES. EVERYONE TURNED OUT TO BE BAD CONNECTIONS IN THE PLUG INS. GOOD LUCK.

 

Well, I was right, the Voltage Regulator had failed ! And the resulting drain (drop in voltage on the battery-ignition system) was causing the spark intensity to fade away (even on a brand new, fully charged battery). I replaced my '86 with a different model year V.R. ('87), and refitted my ATV with individual bullet connectors that are on the newer model and throughly taped up the bundle, and everything works beautifully now.

I was concerned that perhaps the CDI would have failed (and it may have degraded), but everything is working (for now) !

The new V.R. did not meet the specifications of the Clymers manual resistance spec's either (all readings are infinity ohms), but it does work. And it allows the voltage at the battery to climb to a maximum of 14.85v at maximum rpm's, but when lights are on, that drops down to about 13.5+volts which is sufficient power to charge the battery with the lights on, so I am sure that is by design.

Thanks to all those that commented on my request for help.

Sincerely,

CPUjohn
Fox Lake, IL