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View Full Version : Big Red motor upgrade question?



jriley43
03-02-2011, 09:31 AM
I was wondering if anyone has tried putting a Honda TRX300 motor in a Big Red? If so what all did you do to make this possible. For instance did you have to move motor mounts?

TheRealFatShady
03-02-2011, 11:40 AM
The motor is about the same physical size, but you need the original big red (250cc) engine mounts, not the stock TRX mounts.

Other issues:

1. Wiring - easiest way around it is to use full TRX wiring/electrical components.
2. The output shaft is not lined up for the driveshaft to work properly, it's about a 1/4" off. You need to put the 250cc output shaft assembly IN the TRX.

That requires taking off the right side cover/clutch, and then the output shaft. On the end of the shaft closest the clutch, there's a thrust washer, Don't let it fall. Mine fell and I fished it out with a magnet, but it's under an hour to swap if you don't drop it.

http://forum.highlifter.com/250-ATC-with-300-trx-2wd-motor-swap-write-upbuild-m4439445.aspx

There's a basic walkthrough, cell phone pictures. The oil feel hole on the 250cc shaft is smaller, it may work, or may need to be enlarged. I'm waiting on gaskets so I haven't put mine back together yet.

Good luck

jriley43
03-04-2011, 08:48 AM
thanks for the info.... I will let yall know if I decide to go through with it.

250Eddie
01-25-2012, 03:40 AM
Ok i know this post hasnt been opened in over a year but im gonna ask anyways, I was reading this and it had my mouth watering, lol, I wanna know being that they did the swap into a Big red and not a 250sx, Being that the 250sx swing arm is on the outside of the frame and not currently inside of it like the big red, is it possible to swap the engines from the 250sx out and drop a 300 TRX engine in without having to open the engine up and do as they did???? Or will u have to still open the engine up and swap out the parts, i rather keep it as easy as it can get.

TheRealFatShady
01-25-2012, 11:33 AM
Output shaft still needs to be switched, as the 250es/sx whole motor will swap between the two.

250Eddie
01-25-2012, 02:48 PM
awesome :).
Now the thing is for me to find a motor LOL.

86BigRedRider
02-12-2012, 10:24 PM
I picked up a '97 TRX300 motor on eBay. I have swapped out the side output and buttoned it back up and if I'm lucky this week I'll drop it into my ES and be riding it next weekend. I was a little unsure about doing the swap as I had never opened up a bike motor. But I followed what several people on here told me to do and it was pretty easy overall. I did manage to loose the one special bolt for the oil line that I had to get a new one first and a new left handed nut for the clutch as the old one got mangled when I took it off. But it's pretty easy if you take a few minutes and gently guide the output shaft back in while holding all the gears on a long ratchet handle and pushing in while withdrawing at the same time till it's tight against the case. If it hangs about 1/2" out then there is a spacer that has not gone back into place, just push it back out and try again, it will go. I had to do that about 3 times then it just popped in.

Dirtcrasher
02-12-2012, 11:03 PM
The best way is to lay it perfectly on the right side and prop it up with boards so it's level/flat.

Some of those shafts have oil holes that line up with tranny parts so it's pretty important to get it in just as the old one came out.

poplama
04-15-2013, 06:12 AM
has anyone done this with a 250 trx motor? from looking at photos they look pretty well the same?? Would probably transplant the whole loom motor box diff and swingarm. i am considering buiyng a buggy that has the whole driveline of the trx as a rear end. any help would be great!

TheRealFatShady
04-16-2013, 03:35 PM
TRX 250 engines are the same as the 250es/sx I believe. But I believe the swingarms are different, in multiple ways, including length. You can use the stock TRX 250 engine and rear end, but your trike will look like a chopper as the lower shock mount is back about 2 and 3/4" more. You can always have a newer shock mount made, though.

I did have an SX swingarm and TRX swingarm, and the SX one would have be be cut/bent and re-welded to work with the 250 trx rear end, or just use the whole TRX rear. But either way, you don't have to swap the output shafts if you want to put the TRX 250 engine in the SX/ES, only have to for the TRX300.

poplama
04-27-2013, 08:21 AM
Cheers, went and picked up the trx the other night. looks like the swinger is a lot different to the es one, and the whole diff assembly seems to be a bit shorter. looks like the sam brake, hub, and differential are the same but the axle tube seems to be shorter. will pop em both on stands and have a look. might slap the trx together and ride it for a bit and see that its all working gear first before i start engineering :) . have never seen a frame as bad as this trx for rust, dont think it will last very long. The rack fell apart just taking the plastics off and theres real deep pitting everywhere round the important bits, shock mounts etc. hopefully can use a fair bit of it cos i spent more than i should have broke the dont look to buy stuff at night in the dark rule. shot myself in the foot a little i think!

TheRealFatShady
04-27-2013, 02:34 PM
168340

The ES frame is different, it uses the same/very similar rear end as the TRX300 2x4 and 4x4. Only it is longer. The 300 goes with the big red, the trx 250 goes with the SX as far as almost drop it replacements.