1985 250sx motor

[Bustintrukeys]

Hey so I'm tearing down my Honda '85 250sx, I've read through a few threads here about the bike and I noticed that there are some conflicting opinions about the motor and the gearing. From what I can tell both the SX and the 250 Big Red both have the same engine number.

Couple questions

1) Are the two motors the same?

2) If so are the perfectly interchangeable?

3) Is the rear end gearing only major difference mechanically?

[Flyingw]

No, the SX and ES motors aren't the same. The ES has lower gearing in the transmission and the differential. The top ends on both are the same.

[Bustintrukeys]

Okay so how do I tell the motors apart without tearing them down? The engine numbers are the same (TE04E-5000001) I've read something saying SX is black where the ES is steel, this true?

[YamaBoss]

Okay so how do I tell the motors apart without tearing them down? The engine numbers are the same (TE04E-5000001) I've read something saying SX is black where the ES is steel, this true?

That's true unless someone changed colors at one point in time.

[Flyingw]

I don't know why Honda used the same engine number on both as they are different and both have different part numbers. Boss is right, SX is black and ES is silver in color.

[ps2fixer]

Yea the outer cases will be black on the sx, and silver for 250es. Besides the color I'm about 90% sure the cases are exactly the same. The transmission gears are where things are different, and the rear diff is something like 1 tooth different, not a huge change, but a change none the less. AS a whole unit, the engines will swap out, and several engine parts, and the rear diffs can be swapped as well (my cousin's sx has a es diff).

There are free downloads for the service manuals online, so might be a good idea to snag one for each machine.

Also partzilla is a great site to compare part numbers. Left side cover, stator, starter gears are all the same for 250es and sx from 1985. Some parts also interchange to the trx250 too which is basically a 4 wheeler version of the 250es.

http://www.partzilla.com/parts/detai...0-HA0-014.html

[dougspcs]

The 250es and 250sx motors are 100% interchangeable and the gearing differences in the transmission is minimal and is barely noticeable when riding..

I installed a NOS 250SX motor in my ES then had fun with it..called it my 'Back in Black' build..

For me it took away a bit of take off torque, about the same as someone switching from stock size tires to 26". If you're considering a 250ES motor in your frame it will be the opposite..you'll gain torque and lose a small amount of top end speed. Oversize the rear tires one size to bring it back to stock ratio.

My ride isn't as pretty anymore since this was a few years ago..but they never are when you ride them where I do. But at least I have my memories of how pretty she was..

It'll work..go for it!!

[Jdp]

i have a 250sx engine with damaged case halfs can i take the gears from the 250sx and put them into a 250es case? has anyone ever tried to swap gears