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Discussion Starter · #1 ·
Hi guys, I have a 1989 trx300 2wd. Oldie but a goodie. It has intermittently refused to rev up, would run like a dream in between.
Just a bit of background info: I lined the old rusty fuel tank, replaced petcock/ filter, replaced fuel line between carb and fuel tank, new air filter, full carb rebuild kit installed, new spark plug. So the bike starts perfectly fine, hot or cold weather. I never even have to use the choke to start it. However, for the past two week I am unable to rev it up. It idles pretty well, but as soon as I turn the throttle, it starts to buck and spit, almost like dung - dung- dung dung dung. Before it used to do this sometimes, but went like a rocket otherwise. I have sprayed the air filter with starter spray while doing it, and no difference. I guess this means that it is not starved for fuel? Coil and pusle generator test within range using a multimeter. I am at my wit's end. Any help would be very much appreciated. The other funny thing is that, while it is bucking, closing the choke doesn't seem to affect it at all, choke only kills the bike when idling.
 

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Bad CDI would be my guess.

Rick

Sent from my SAMSUNG-SM-N900A using Tapatalk
 

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It is spark control, spark advance all the time. Don't waste your money on a Chinese replacement. Go OEM Honda or get one from "Rick's", I think is the name . . . and no, not me.

Rick
 
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Before buying any expensive parts I would diagnose it better if it were mine. I have a question and a tip:

Which brand did you buy for your new spark plug? Hopefully NGK or ND? Champion plugs are junk in motorcycle engines.

Have you verified that the spark plug wire (coming from the Ignition coil and plugging into the spark plug) is not going bad? Try this: untwist the spark plug boot off of the end of the spark plug wire and look into the boot to see if the screw post in the center is not burned off or broken off. Then cut about 3/8" of the end of the spark plug wire off (a clean square cut, sidecutters or ***** work fine for this) and throw that short chunk of wire away. Twist the spark plug boot back onto the end of the spark plug wire that you just cut off and test the motor.

Did that fix it?

Come back and tell us about it before spending cash on something that no one can be sure will fix it. I can think of several other possible causes, so please follow up with this.
 

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Discussion Starter · #8 ·
Thanks for the info Retro. Will have a look at plug and cable today hopefully. Fishfiles, are you referring to a timing chain? Will check out the manual for tips on how to access. Thanks heaps guys!
 

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Did you put an OEM carb kit in it or was it a chinese knockoff kit? If it was not an OEM kit (it doesn't sound like it was, because you said you don't have to choke it for cold starting) then ya gotta go back and undo that mess before you can continue.
 

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Discussion Starter · #10 ·
Well, touch wood but the bike has been running perfectly for the last week or so. Turns out B52 was pretty hot with his guess. I decided to pull the cdi box of to check for model numbers etc, the contacts were quite dirty! Cleaned it up a bit and re installed. Hasn't missed a beat since! Thank you so much for all your advice guys...learning all the time!
 
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