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Hi everyone! I bought honda trx 300fw -91 last week, and it had not been driven since last summer. First it runned perfectly, then suddenly it stalled. I thought something is wrong with the spark plug. I have diagnosed this problem for a couple of days now. I have tried new ignition coil and spark plugs etc. No difference. I started to doubt the condition of the cdi unit. I found out that when the engine stalls and won't start, you need to wiggle the cdi unit and it starts running again and works some time before it stalls again. My question is, is the cdi unit broken or am i having problems with wiring? When it stalls im having spark only randomly, and when it starts to work, i get constant spark. The seller said that it worked beautifully last summer, starting to doubt it..

Another thing i need to ask is this other box next to the cdi unit. In the wiring diagram it says "alarm unit". What does it actually do and can it effect the spark? It has an identical connector as the cdi unit.

Best regards, Jouni Takalo
 

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The alarm unit is just for oil temperature - it has nothing to do with spark - when you turn the key on, the light should light for a few seconds and then go out - if it does this, the unit is working properly

If you can wiggle the wires on the CDI unit and get it working again, it's probably just corrosion in the connectors - unplug them, spray them with electrical terminal cleaner, coat them with dielectric grease and plug them back together, also loosen and re-tighten the frame ground connection at the ignition coil and battery - if this solves the problem, you are done - if this does not solve the problem, it might be a bad pulse generator (ignition signal coil) or any of many wiring connections including the battery, fuse, coil connections, intermittent ignition switch or handlebar kill switch.

Hope this helps
 

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Huge Thanks for the tips and quick response here 2 help! So you think the cdi unit is not broken? What kind of procedure is it to change the pulse generator? One thing i was suprised of was that the stator was under oil. I mean is it supposed to be..? I removed the coverplate from starter motor gearings and noticed that you can see one of the stator coils from there. I have never seen stator that is swimming in oil, thats why i am wondering.
I did disconnect the plugs from cdi unit and there was no corrosion in them. Is there any other connections in those stator wires that might be affected from me wiggling the wires?
 

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Yes, the stator runs in oil - most utility quads have stators that run in oil. It's the same oil the engine runs in - drain the oil and you have drained engine, transmission, alternator and drive unit.

Changing the pulse generator requires removing the alternator cover (and draining the oil) - good news is; parts are available and not too expensive - bad news is; the pulse generator might not be bad - it should be tested first. The CDI could be bad, but usually when the CDI fails, the spark is gone forever - very rare to have an intermittent CDI unit. More likely to have a bad coil and they don't fail very often. Connections are most generally the problem with a problem that comes and goes.

There is a connection between the stator/pulse generator and the wiring harness before it gets to the CDI unit - be sure to check it also. And make sure the oil level is correct - you should not be able to see the oil level by taking off the starter gear cover.
 

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Ok! I have to check all connections and the oils also! I'll come back to tell if i found solution to my problem or if it's still present! Thanks for the tips! I will not buy new cdi unit until i check and clean all the connections.
 

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When you said "more likely to have bad coil", do you mean the ignition coil? Also one thing i may aswell ask, no that i found someone that knows about this atv.. Why is my atv twitching(if thats how you say it) or trying to move, when i put it in gear. The idle is very low so thats not the problem. I tried to adjust the clutch but it seems that it didn't have any effect on it.
 

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Too heavy grade or incorrect rating of oil presently in crankcase

Needs to be JASO rated M or M2 or API rated SJ or lower - I don't know how oil is rated in your part of the world, but if you get Honda oil it will be fine
 

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Agreed - the oil is probably not the problem

So it's either normal or a clutch problem - I have seen a single spring break in the centrifugal clutch (there are 4) causing a problem similar to what you describe. If you can't live with it and decide to investigate, just replace the 4 springs as a matter of maintenance. otherwise, ignore it till it gets worse. There is no adjustment for the centrifugal clutch - the adjustment screw on the clutch cover is for the manual clutch - the manual clutch is released during shifting by a device attached to the shift shaft. You can manipulate the manual clutch by pressing or holding the shift pedal. Practice this on a level surface by shifting slowly - shift up or down and hold the pedal, the clutch will be released and operating the throttle will result in engine speed changing without vehicle speed responding. Slowly releasing the shift pedal will result in gradual engagement of the clutch - useful in situations where you desire to maintain constant engine speed and partial application of the drive without shifting gears and relying on the auto clutch for manipulation.
 

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Discussion Starter #11
Ok, i have to try these tips! Back to the spark. I ordered new cdi unit, because it was only 97 euros. Even if thats not the problem, it is not a huge money to pay. I will clean all the connections and report you, if it starts working.
 

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Discussion Starter #13
Ok, im back. The problem was faulty cdi unit. I changed it and now it runs perfectly. Thanks for all of your advice an tips, now i can just enjoy riding my atv, and dont have to fear when it stalls again!
 
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