Honda ATV Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter · #1 ·
k, so I got a 300ex engine with a bad crank and top end. I bought a complete 250x engine with a fresh rebuild with the intention of putting it in the 300ex but as i was bolting it in I noticed that the idiot overtightened damn near ever side cover bolt and cracked the case in several spots. So my question is, can I put the 250x crank and top end in my 300ex bottom end?? And basically end up with an electric start 250?
 

·
Registered
Joined
·
1,963 Posts
Hello and welcome to the forums! somebody with the sport quads will help you shortly.
 

·
Super Moderator
Joined
·
18,230 Posts
Check you other post.... but to answer here too....NOPE the crank on the 300ex is longer on one side to accomodate the starter housing.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #4 ·
Oh! longer that way. I see what your saying. Is there any way to do it? Can I use the kick and not use the electric start?
 

·
Super Moderator
Joined
·
18,230 Posts
As stated above... no you can't the case is a little wider on the 300 to accomodate the wider crank. the stroke is longer too but that dosen't matter. the top end is Identical though. As far as the quads go the frames are Identical and the plastics are Identical.
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #6 ·
k, im gonna stick to this post. Its getting too confusing going back and forth, lol. The rod is what is bad on the 300. The machine ran but didnt sound healthy. I tore it down and the rod has quite a bit of play. Im just trying to make one good motor out of two without spending any money, minus gaskets of course. k, so you say the crank is longer on one side of the 300ex? So is the other side the same? Could I use one case half from a 300 and one from a 250? Im bound and determined to get this thing going. Come on! give me some hope! lol
 

·
Super Moderator
Joined
·
18,230 Posts
I don't think you can split the crank bro. Just buy a new connecting rod and bearing you should be good then but you will need to deglaze the cylinder and replace the Rings. it's kind of crazy not to! and cheaper in the long run on your wallet
 

·
Registered
Joined
·
7 Posts
Discussion Starter · #8 ·
cool. Thanks man. I should be alright with the cylinder though. Im using the one from the 250x which has never been ran. As long as I use the 250 piston along with the 250 top end I should be good to go right?
 

·
Super Moderator
Joined
·
18,230 Posts
The pistons are the same form the jug up to the cam they are the same engines the oil pumps are the same the tranny gears are the same the crank and electric start set them apart.
 

·
Registered
Joined
·
2,735 Posts
Moose you can split the cranks with the right press.
 

·
Super Moderator
Joined
·
18,230 Posts
Too much work IMO all he needs is a rod and bearings. Not really worth it besides if you do not know what you are doing you can cause more harm than good.
But isnt the shaft one piece? that is what is screwed up about the 300 and 250 so splitting wouldn't do anything. you still can't use the 250 crank in a 300.
 

·
Premium Member
Joined
·
23,581 Posts
Too much work IMO all he needs is a rod and bearings. Not really worth it besides if you do not know what you are doing you can cause more harm than good.
But isnt the shaft one piece? that is what is screwed up about the 300 and 250 so splitting wouldn't do anything. you still can't use the 250 crank in a 300.
You have to press the crank apart to change the rod and rod bearing. It's better to just buy a whole crank assembly. They hold up a lot better.
 
1 - 12 of 12 Posts
Top