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Discussion Starter · #1 ·
I have a good running 1986 TRX250A Fourtrax engine in a rusted out frame and a good 1999 TRX350 Fourtrax frame complete that I don't have a running engine for , was looking it over and it looks close to being the same ------I think this would make a really good bike , I think the 5 speed 250 is much more powerful and responsive than the 300 engine , and the 300 is a much better suspension and frame than the 250 was , the 250 as far as I have read is the Big Red three wheeler engine -----------anyone tried this swop out yet
 

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I have seen this done but never tried it myself I think you have to do something with the drive shaft\ u joint I'm not sure if they are different lengths or not I could be totally wrong I don't think it would be hard at all I'd say maybe a day to swap it out
 

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Discussion Starter · #4 ·
I had taken the rear end out the 250 and put it in a 300 , I was moving the frame and the shaft fell out the swing arm , I threw the shaft in a box with parts with 3 or 4 other 300 shafts so now I don't have a clue which shaft went to which one , going to have to lay them all out and check to see if one is different , hoping to get time this weekend to pull the 250 engine off the frame and put it next to a blown 300 engine I have to see if there is any differences in the out put shaft and what is the total length of the u joint and shaft of both the 250 and 300 while out of the swing arm ------------ I have collected all the parts to build another 250 rear end to put on the 300 frame , only thing I would be missing to build the bike would be fenders --------------- I am pretty hyped up about this build , last weekend I swopped tires on my running 250 , put 25 x 12's in the rear and 25 x 8's in the front ( and they don't hit ) , it had worn out 25 x 10 in the rear and 23's in the front then went for a good ride with my buddies , I don't ride that bike a lot and kinda gave it to son in law , but that engine is bad to the bone , good thing that bike has good brakes , I am not sure if the one way bearing is bad or it is just the characteristics of the bike , but it free wheels very easy , in other words when you let off the gas it doesn't brake thru the engine nearly as much as a 300 and will coast further
 
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