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Okay so I bought a Honda FourTrax says on the front of the frame is a trx300 when I went to replace the top in I bought a used motor which I was told was in 300 when I tried to connect the piston to the connecting rod on my original motor the wrist pin was too big now I'm kind of lost not sure if the motor on this FourTrax is a 300 or 250 or vice versa
 

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look on the side of the jug there are cc marks , 246 is a 250 , 281 is a 300 , the jugs are interchangeable , the heads are also the same on the 250 and 300 except , the 250 doesn't have a decompression lever
 

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Discussion Starter #3
My bike Reeves is a 300 TRX but did not have a compression release nor did the other motor I bought the juggling it reads 250 the one on my bike reads out of there 300 but when I tried to put the piston on the wrist pin was too big
 

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You have a 2wd bike correct? Sounds like someone has put a 250ES motor in it. The 250ES has a bigger wrist pin hole in connecting rod.
 

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You have a 2wd bike correct? Sounds like someone has put a 250ES motor in it. The 250ES has a bigger wrist pin hole in connecting rod.
he could also have a trx300ex cylinder on the motor as well ??!!.
 
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op, post some pics of your atv, then we can narrow down your problem. pics of the motor will be lots of hep :).
 

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You have a 2wd bike correct? Sounds like someone has put a 250ES motor in it. The 250ES has a bigger wrist pin hole in connecting rod.
he could also have a trx300ex cylinder on the motor as well ??!!.
Possibly but I doubt it. If it does that's extremely weird. Unless.... idk im stumped... we need some pics please!!
 

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You have a 2wd bike correct? Sounds like someone has put a 250ES motor in it. The 250ES has a bigger wrist pin hole in connecting rod.
he could also have a trx300ex cylinder on the motor as well ??!!.
Possibly but I doubt it. If it does that's extremely weird. Unless.... idk im stumped... we need some pics please!!
these days ?..I don't put nothing past what ppl slap together !!..lmfaoooo.
 
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If your struggling to identify between 250 and 300, just look at the carb, that would be the easiest way to determine what engine you have.
The 300 carb has a round upturned dish shape on top, the 250 has a flatter triangular (ish) shaped top.

Obviously you could have a different carb fitted so this would only apply to a stock setup.pictures would be useful though I must admit :)
 

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once again op, POST A PIC OF YOUR MOTOR. haha, and here ya do..right as I posted..lol.
 

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both engines look like trx300 motors, but I do know the trx300's had a decompression lever on the top right side of the rocker box.
 

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looks like you lost the info from your other thread ------- maybe you should mic the wrist pin and piston , with all the exotic build going on now days , you could have a 355 , 317 and I think there is even a 383 or such
 

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yeah that's what threw me for a loop was neither one had a decompression valve and all the forms that I read said a 250 would fit a 300 and it all did except for the wrist pin and The Jug on the spare motor read a 250 so I'm just going to go with an over bore piston use the old jug and hope for the best thank you for your information
 

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yeah that's what threw me for a loop was neither one had a decompression valve and all the forms that I read said a 250 would fit a 300 and it all did except for the wrist pin and The Jug on the spare motor read a 250 so I'm just going to go with an over bore piston use the old jug and hope for the best thank you for your information
who knows what size crank was installed in that trx300 motor ??!!..lol.
 
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