Atc250es engine/rear diff into Atc250sx frame?

[ShaftDrive225dx]

I searched the old threads but couldn't find the answer, I have 85 atc bigred 250es that I got for free from a friend. The frame was in rough shape and missing all the plastics! The bike runs very well; I got my hands on a 85 Atc250sx frame and front end, well my 250es engine/differential, swap right over?


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[ShaftDrive225dx]

240756
Here's a pic of what she's like so far, I just don't like the 2 piece fender option for the big red! I like the sportier look of the sx


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[dustrunner]

does you sx have the swing arm on it ? if so take your rear diff. off the big red and bolt it in and everything should be fine..

[ShaftDrive225dx]

does you sx have the swing arm on it ? if so take your rear diff. off the big red and bolt it in and everything should be fine..

I don't it's just the frame; Is the swing arm different than the big red? It's an 85 sx frame as well...


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[Dirtcrasher]

There are year and models that shared a swinger or same piece, but my record keeping records are amiss.

ES is just an SX motor with electric start, that's enough to know it's swaps into another models cradle....

[fabiodriven]

There are year and models that shared a swinger or same piece, but my record keeping records are amiss.

ES is just an SX motor with electric start, that's enough to know it's swaps into another models cradle....

https://uploads.tapatalk-cdn.com/20170316/934526f3d68806ab9063e7ac8f340e5a.jpg

[fabiodriven]

Engines are identical. Direct swap, yes.

[ShaftDrive225dx]

Engines are identical. Direct swap, yes.
Thankyou, for your response lol I didn't know exactly how to respond to the comment before yours! I was a little lost [emoji23] I seen the threads speaking on just the engine swap; but my question is will my swing arm/differential from the es bolt right up and work on sx frame along with es engine?


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[fabiodriven]

The swing arms are interchangeable but the ES has lower (higher numerically) gears than the SX to make up for the 25" tires. So SX rear is your highway gears, ES rear are your tractor gears.

[ShaftDrive225dx]

The swing arms are interchangeable but the ES has lower (higher numerically) gears than the SX to make up for the 25" tires. So SX rear is your highway gears, ES rear are your tractor gears.

Ok sweet thank you very much for your help tractor gears are good with me!


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[Name Brand]

I don't belive the swingarms will swap over. The SX has inboard pivots to meet the frame and I really think the ES pivots are outboard.

The engines are dimensionally the same and will swap between frames but the gearing in the transmission is different. ES has some lower gears. I use to have a little chart that showed this but can't find it now.

Since all your parts are '85, I would use the ES engine in the SX frame with SX swingarm. The ES rear diff had lower gears also. You could use either but I'd stick with the SX rear diff to keep the speed up. You'd have a torquey machine with the 22" tires. It would be geared really low with the ES diff and would need a 25" or so tire. Course that large won't likely fit a stock swingarm.

There's a link by the SX in my signature to make the gears in your head turn more. My SX; SX engine, TRX250 swingarm and rear diff with 25" tires.

[ShaftDrive225dx]

I don't belive the swingarms will swap over. The SX has inboard pivots to meet the frame and I really think the ES pivots are outboard.

The engines are dimensionally the same and will swap between frames but the gearing in the transmission is different. ES has some lower gears. I use to have a little chart that showed this but can't find it now.

Since all your parts are '85, I would use the ES engine in the SX frame with SX swingarm. The ES rear diff had lower gears also. You could use either but I'd stick with the SX rear diff to keep the speed up. You'd have a torquey machine with the 22" tires. It would be geared really low with the ES diff and would need a 25" or so tire. Course that large won't likely fit a stock swingarm.

There's a link by the SX in my signature to make the gears in your head turn more. My SX; SX engine, TRX250 swingarm and rear diff with 25" tires.

Wow! Dang a I was hoping it would; but sounds like I better look into a sx swing arm... Thankyou for the help!


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[fabiodriven]

I apologize if I was mistaken! Thought I knew all of that for fact...

[fabiodriven]

Engines are identical. Direct swap, yes.

https://uploads.tapatalk-cdn.com/20170317/64413a3a1dfe42a1e19baa261584b199.jpg

[Dirtcrasher]

Hey , I may be just like the others. I'm so far away from the SX/ES, but I use to know that model very well.....

Your ES transmission is also a bit different than the 250SX, but yes, it bolts in.

As far as the right angle gearbox output, I'm not sure if it's exactly the same (I gave away my ES motor just a mere week ago).

And the swingarm, take a look on EBAY, pictures of the Big Red swinger appear to be far different than the 85 or 86/87 250SX.

Sometimes these guys can't get an answer at all which is why I chose to say "something", although not very informative at this point..... But I digress, I can't recall all of it but I do keep records in a book (which is buried somewhere), but I can't find it at the moment.

Anyhow, as I said along with others, the 250ES (although it does have some differences) does fit right into the SX cradle. But, I don't think the Big Red swingarms fit. Search for more posts, they are here at 3WW somewhere....

I am positive there is a thread somewhere about these swaps. I recall an upgraded 300cc motor that has a few changes that need to be done to get it all together.

As soon as I can find a 30' long shipping container, I can get back into all of it. My 20' x 16' shop can only do so much; Which is why some ATC's are in my basement.

Anyhoo, keep looking and posting, the answer is here at 3WW somewhere and I bet Ryan Dailey knows exactly whats up. I'm not sure what his board name is, but I will figure it out and try to send you in the right direction.

The sad frog says it all, pretty accurate picture.....

[atc007]

The answer to the OP,is, yes,as said, the engine switches right over.No, the swingarm won't. I would just stick with the BR,but that's just me. If you go mixing parts. It is imperative you stick with ALL 85 rear parts. 86 up are completely different hub to hub.. It sounds like with a 85 SX swingarm,you might be in business. As said, the gearing in the engine and rears are slightly different,but nothing you will probably notice.

[ShaftDrive225dx]

The answer to the OP,is, yes,as said, the engine switches right over.No, the swingarm won't. I would just stick with the BR,but that's just me. If you go mixing parts. It is imperative you stick with ALL 85 rear parts. 86 up are completely different hub to hub.. It sounds like with a 85 SX swingarm,you might be in business. As said, the gearing in the engine and rears are slightly different,but nothing you will probably notice.

Yea forget it I'll just keep the frame around I think it might be a little over my head! It runs good he way it is...
thank you for the help!

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[atc007]

Unless you are racing. You will LOVE the Big Red. Hands down the best ATC ever made. The 25 inch rubber makes them just a terrain eating machine. New plastics aren't too bad in price and you will have yourself a nice machine. All that said. Check your diff oil, change it and if it looks good. You're probably good for another 30 years.

[captainweezy]

Unless you are racing. You will LOVE the Big Red. Hands down the best ATC ever made. The 25 inch rubber makes them just a terrain eating machine. New plastics aren't too bad in price and you will have yourself a nice machine. All that said. Check your diff oil, change it and if it looks good. You're probably good for another 30 years.

I love my big red. I am guilty of changing the rear end fluid more than once a year. Its so cheap and easy. Right before trikefest and usually in winter at some point.

[Ranvier]

Unless you are racing. You will LOVE the Big Red. Hands down the best ATC ever made. The 25 inch rubber makes them just a terrain eating machine. New plastics aren't too bad in price and you will have yourself a nice machine. All that said. Check your diff oil, change it and if it looks good. You're probably good for another 30 years.

My first trike and got me addicted!

[Dirtcrasher]

Absolutely; Guys think an 85 differential and a driveshaft as well as bearings, can go thru 30"s of water.

Snorkel or no snorkel, rebuild one and you'll never play in the water again.

Zinc coating has worn off, the 85 250SX whole rear end seals terribly. 86/87 is a bit better but I don't want 30 year old PLUS in too much water.

Or if you must make a submarine out of it, take it apart to inspect, put a new boot on and new seals and play in the mud/water for awhile.

I just don't want to destroy stock journals and other parts that I may not be able to buy......

[fabiodriven]

Mine is like a gall-danged submarine. I take it in deep water and I do so often. That's how and where I want to ride and the SX/ES's were made for that and excel at it. I couldn't even count the number of rivers we crossed in NH last month, and the snow was melting so they were DEEP. Five bikes, two SX's and three ES's. Check your diff oil often, it's very easy to tell if you have a leak. Simply change the oil and fix the leak if it's bad enough. I've been hammering on my 86 SX for years since I've gotten it, it's seen a ton of water. Probably been at least five years anyways, maybe more. I have never changed the diff oil. It's due so I'll open it up soon and report how five years of abuse has treated it. These machines are true all terrain cycles, including mud and water. I agree it's best to take care of the bike but the care of the rear of these bikes is just different, not to be mistaken with inferior. For the type of riding I do they are actually far superior. Don't be skurred to sink it as long as you keep an eye on your diff oil.

[Name Brand]

Leave the Big Red together and enjoy having 25"s.

Prep the SX frame for another build. Find yourself an 86-87 TRX250. It is a rear wheel drive utility quad. It's the same 250cc engine, use the entire wire harness and the entire swingarm, rear axle and wheels on the SX frame. The TRX swingarm is about three inches longer than an SX and will allow a 25" tire on an SX. You will have to fab a new lower shock mount. I narrowed a rear rim to about eight inches wide for my front tire and have a Goodyear ATT912 in 25x11x9 on the stock SX front. I'm a big fan of the Kenda Bear Claw; I run 25x12.5x9 on my SX. From that one TRX250 you'll have many of the parts you will need to build a Big Red/SX combo.

On any machine run the vent tubes as high as you can if you're anywhere near water. Mine are plumbed into the top of the airbox and I made a removable snorkel. I haven't had any water intrusion since doing so, but do keep checking those fluids!

[ShaftDrive225dx]

Leave the Big Red together and enjoy having 25"s.

Prep the SX frame for another build. Find yourself an 86-87 TRX250. It is a rear wheel drive utility quad. It's the same 250cc engine, use the entire wire harness and the entire swingarm, rear axle and wheels on the SX frame. The TRX swingarm is about three inches longer than an SX and will allow a 25" tire on an SX. You will have to fab a new lower shock mount. I narrowed a rear rim to about eight inches wide for my front tire and have a Goodyear ATT912 in 25x11x9 on the stock SX front. I'm a big fan of the Kenda Bear Claw; I run 25x12.5x9 on my SX. From that one TRX250 you'll have many of the parts you will need to build a Big Red/SX combo.

On any machine run the vent tubes as high as you can if you're anywhere near water. Mine are plumbed into the top of the airbox and I made a removable snorkel. I haven't had any water intrusion since doing so, but do keep checking those fluids!

Yea I will! Thanks for the advice I came up on a great deal purchased this atc250sx runs good cosmetics need help but that's easy! Going to put some 25's on it as well! https://uploads.tapatalk-cdn.com/20170420/214073ade6c94c457e156f2e34cd459a.jpg


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