Honda TRX ATV Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Hello, I have a 1991 trx 250x. As my son was riding it the other day, he said it made a funny noise and now it misses very bad after about quarter throttle. It misses almost like it is hitting the rev limiter. I thought it jumped time. Took the valve cover off, found top dead center and timing is correct. The valves and cam are in excellent shape. No valves are bent. We have another 250x, so we began swapping parts to see what the problem could be. CDI swap did not fix it. Coil Swap did not fix it. Put new grounds on to see if it was a bad ground. Swapped carb just in case. Checked all wiring to no avail. We have spark. It will start easy and idle great. We have good compression. We put in a new spark plug. Then I thought maybe the flywheel key sheared and that changed the timing. Flywheel and key intact. There is a little side to side play in the crank, but I could not see how that would cause the symptoms we are having. I am at a dead end. Thought maybe pulse sender, but they rarely fail and I have spark. Bike runs like a new one until quarter throttle exact same symptoms every time. I am lost.
 

·
Super Moderator
Joined
·
3,571 Posts
I suspect either a stator or flywheel magnet problem - does it run the same with the lights on and off? If it improves with the lights off, it's definitely a wiring connection (including grounds) the stator or flywheel. The rev limiter is incorporated into the CDI unit.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #3
The lights have been removed completely so no way to check that way. The stator was a thought but everyone says they usually work or not. I have good spark. Is there a way to check the stator besides an ohm test. Not sure how to check flywheel magnets.
 

·
Super Moderator
Joined
·
3,571 Posts
Stators go bad more frequently than any other part of the ignition system other than switches. Testing the stator is best guess at best. A friend of mine told me he lost spark on his Honda and I told him to install a new stator - he wanted to test the ignition system and make sure he didn't replace anything that was not needed - he used my manuals and my meters to test the ignition - the only part that tested good was the stator, so he first replaced the pulse coil (on his it was a separate component on the RH side of the engine and got it's signal from the crank pinion or clutch gear) followed by the coil and then the CDI box - he still had no spark - I said replace the stator, he argued the stator tested good - I asked what part of the ignition system had he not yet replaced and he knew it just the stator and flywheel - he replaced the stator and walla, SPARK! He then swapped back the coil and CDI box and still had spark. He did not replace the pulse coil because he would have to dump the oil again and just didn't want to do it, but in his mind he knows the old pulse coil was good also.

You can't test the flywheel magnet with out a Gauss meter which is very expensive and usually only found in laboratories and manufacturing facilities where magnets are produced. I used one when I worked as a lab technician at General Electric. If the stator does not fix it, then you might suspect the flywheel. In my life time I have only seen one flywheel with weak magnets and one that lost the tab that triggers the pulse coil. All other bad flywheels were damaged by the 'mechanic' working on it or from nature (rusted to the point of loosening the magnets from the rotor.
 
1 - 5 of 5 Posts
Top