SX / TRX Compatibility?

[DasUberKraut]

Here's my question of the day.

I'm acquiring a TRX 300 4x4 dirt cheap that I was just going to part out. A thought occurred to me. They made the 300 kits for the SX as a bolt on mod. Any chance the TRX top end will fit the SX bottom end? I know people have swapped the entire 300 motor into an SX or ES. Obviously that's only the 2WD version. The 4WD version would never work in an ATC.

Thoughts and ideas?

[Trike_crazy]

I would swap the stator cover and flywheel from the sx to replace the stator cover on the 300. The 300's cover has the drive on it for the front diff. I think it would be a pretty easy swap. Also would have to swap the output shaft

[Trike_crazy]

I would swap the stator cover and flywheel from the sx to replace the stator cover on the 300. The 300's cover has the drive on it for the front diff. I think it would be a pretty easy swap. That would also let the stator plug in the harness. Also would have to swap the output shaft

[DasUberKraut]

I don't want the whole motor. My question is if the the top end from the TRX will swap to the SX bottom end?

[Trike_crazy]

It will. The 88-2000 fourtrax top ends are the same as the as the es/sx. The bore is the same so you won't gain any cc's from it.

[DasUberKraut]

That makes absolutely no sense. You're trying to tell me a 300 cc cylinder is the same as a 250 cc cylinder. I'm not a genius by any means... But I know enough to know that's asinine.

Why don't you think that over for a minute.

[Bren_downe]

Whoa!… easy kraut, I've read many times the bores are the same. The stroke on the 300 is longer, which is where the extra cc's come from.

[DasUberKraut]

Right. But I said the entire top end. That includes the rod and piston. It would actually get rebuilt with a Wiseco high comp piston. Therefore it would still be 300.

I apologize if I come off rude. Guy didn't even read my question and gave two answer that didn't even pertain to what I was asking. It's just annoying is all.

[6speedthumper]

Technically the rod is part of the bottom end.

[6speedthumper]

And, changing out the rod will not increase stroke. Stroke is the offset of the crank pin (what the rod is attached to) in relation to the crankshaft, measured center to center. You need to change the entire 300 crank over to the 250 cases, and use the 300 cylinder and piston. So, if the engine runs, swap stator cover, flywheel, rear output shaft and call it a day.

[Trike_crazy]

For your information. I did read your question. As a matter of fact I read it twice, once when I seen it the first time and the 2nd time after I logged in to help your very unappreciative self. I was only trying to tell you it would be easiest if you wanted 300 cc's to swap covers and be done. Im sorry if you didn't provide anymore info on what was wrong with either engine. AND I MAY NOT BE A GENIUS BUT I HAVE ENOUGH BRAINS TO LOOK UP THE PART NUMBERS AND FIND INFORMATION ON MY OWN. Have a nice day

[Trike_crazy]

This is what I have found for the bore/stroke of the 250 and 300 engines.

ES/SX/TRX 250 bore and stroke - 74.0 X 57.3mm (2.91 X 2.30in)

Fourtrax 300 bore and stroke - 74.0 X 65.5mm (2.91 X 2.58in)

And below is the link to the latest part number for the 250/300 cylinder. Notice the SX isn't listed but its the same cylinder as a 250ES/TRX which is listed, the SX cylinder is just painted black. But you knew that right?
http://www.partzilla.com/parts/detai...0-HC4-000.html

[DasUberKraut]

Well that's some info I can work with. Thank you.
Yes, I did know the SX is painted black.

[Trike_crazy]

Hey, no problem. I was only trying to help. Im in the process of building my own SX with a 99 trx300 engine that is going to be 300+ cc's when I'm done so I figured I pass along what I have found out in the process. I didn't mean to seem asinine or anything, honestly I wasn't. So I appreciate the thanks and I hope your project goes well.

[DasUberKraut]

The problem with the TRX motor is the case is blown out and patched. It's a runner but a beater/mudder. I'll probably just hold out til I can find another SX Big Bore Bomber kit. I missed one for a $100 a couple months ago. Kicking myself since. I'll keep the TRX whole.