I am thinking of buying a 1991 250x with a 350x motor has anyone ever had one or know anything about it? Would it be a good choice for mx racing?

 

well u would have to race in the 400 class but it has been done many times and works great as far as i know.. also poweroll sells a kit where the engine and everything bolts right in all u need is a cdi box and it comes with the mounts and everything to work! well hope this helps! if i was u i would just stick a stroker crank in ur bike put a big bore kit in it and raise the compression and get a bigger intake and exhaust side take put on it and then port and polish that bike and get a good cam and u will be happy with that and u can race in tha smaller class with tha blasters and other small quads Oh if i was u i would invest in some great great suspention and everything like that... ebay sells a kit that makes ur bike able to handle longer shocks like tha 40oex and 450r shocks well hope this helps!

 

I've done it. I had an 87 250x and I bought my friends 350x. Everything that you need bolts right into the 250x frame from the 350x. The motor goes in from the left side the easiest. Bolt for bolt the engine sits there nicely. Except for the very top head bolt, you have to weld a mount under the tank area. The swingarm bolts right in there too. It's nice cause it's a bit longer than the 250x stocker and nice for the added power.

The CDI box IS needed from the 350x also as mentioned. And...if I recall right, the 350x pipe goes in, but it's a PITA !!! It works fine though.

It's one hell of a machine by just doing the engine swap. BUT.......it can be way better too [img]i/expressions/face-icon-small-wink.gif[/img]

 

isnt that a little too much engine for such a small bike.... I love the 350x engine but the suspension is a little small for all that power, I had a 300ex and well I have a 300ex and going much faster on a small bike isnt fun... you should def invest in some suspension.... as someone else said theres a kit to upgrade shocks for the front and its a big help, i upgraded to 400ex shocks and it was great, needed more in the rear though.

 

I did it also and still have the bike. I have an 86 350x crate motor in an 88 250x frame. i wont say what everyone else already has but it is a pretty fun bike. I ended up running a 400ex carb on it and put the cheapest Works dual rate front shocks on it. The 350x pipe doesnt fit though. . you have to do some fabricating to make it work. Anyway. . not a bad bike at all. . small bike. . .good power. . especially if you were to build the motor. A few years ago i raced my buddy on his Warrior (I know, nothing great) but still. . he had some work done to it and i was neck to neck with him every time. Call Powroll and do thier kit for it and you'd probably have a good time racing it. Might wanna try to lower it in the process since its pretty short and narrow. good luck.