ATC300ES Bigger Red???

[Jugernaut]

I heard tell the top end from a Honda 300 fourtrax will work on a ATC250ES engine. I also heard that the 250's head should be used.What about the stroke of the 250 compared to the 300?? anybody heard of such a swap??? any input will be appreciated.

[Jugernaut]

Anybody??

[bbechtel16]

I don't know but that would be really nice because then it would work on the 250SX also right? Right now I just wish I could get mine running. :( Your fleet is very similar to mine I see. Anybody have an answer to this?

[Tweeked]

bbechtel16,
Do you have all the shaft parts to fix your problem? If not, Try ebay---I see several shaft assemblys going for a cheap price. Just thought i'd ask.

[Jugernaut]

I was told that the trx300 cylinder is a direct bolt up,but will not increase the cc's;the difference is in the stroke.However,I was also told the 250ES/SX cylinder head was the preferred head for performance increases;the SX head being the best because of better valve and cam setup.There is supposed to be a "big bore kit" for the 250ES/SX available,but I have yet to find one.

[Tweeked]

Hey,
I was just on ORG and saw the same thing you'd posted. I wonder if changing the valves and camshaft like you said, would increase the power? And if its possible, or reasonable.

[bbechtel16]

I got the parts, I bought a parts trike from a local shop that suposedly had a bent connecting rod. When we took it apart we found that the connecting rod was fine, but the engine was siezed. So I had the cylinder bored to fit a 2mm (260cc) high compression (10.5 to 1) piston from www.powroll.com That is the only bore kit I know of for the SX, not really a "big" bore, but still decent. We put it back together yesterday at school (we go to a technical high school), after toiling to get the spark plug out of it when it broke off, resurfacing the cam journal or w/e its called, and replacing the intake valve. While putting it back together I noticed that the bottom of the case was plastered with JB weld! :( On the way home (we brought the engine home on the bus lol) I noticed there was a freaking hole in the head! So when I got home I had to swap heads with my original engine. Well I got my head off the parts trike engine and was starting to take the head off the original engine when my friend who is in the outdoor power shop called for me to come pick him up to help me. He came over and we swapped the heads. But for some reason we were having a horrible time getting it timed. And my friend broke my blippin camshaft when he tried to force the engine to turn. So we used the cam from the other engine. So then we got it all timed right and stuff and it was kicking over well, and we had the tensioner in. Then we put it in the frame and secures 2 of the engine mounts. Then we checked for spark, and surprisingly we had spark no problem. So then we started filling the case with oil. After I had about 1.5 quarts in my friend started kicking it over to check for top end lubrication. He kicked it 5-10 times then it just went and locked up!!! :x We figured it must be a valve acting up so took the engine back out and removed the valve cover. But it was still locked up. But then we found we could turn it with the 17mm socket through that cap screw hole in the case, but the kicker still didn't work, and it was making a bit of a strange noise. We gave up for the night before we broke something else and we are going to try to tackle this again tonight. I can't wait 'till I'm done messing around with this thing and it runs. I wish I could afford to have a real mechanic work on this thing. Please offer some suggestions. BTW: As far as we can tell when the cam broke no pieces fell into the case because the 2 pieces mated together almost perfectly.

[bbechtel16]

She's running now :-D :-D :-D Like a champ, well, not really. It's rich on the needle jet, and I think my valves are tapping a little. But oh my the torque! She kicks over like my friends 250R now, well not quite that bad. I guess my compression release probably doesn't work. So I guess tomorrow I'm gonna take off the valve cover and double check the timing, then I'll double check my rocker/valve clearance, then I'll attempt to adjust the carb.

It's a crazy arrangement on there now. I got my original head and right side case (the parts trike side case was all JB welded). And parts trike bottom end and jug. And powroll piston.

BTW: That hole in the head was susposed to be there. I realized it today when I saw it was also on my other head. (duh) Also the reason it locked up like that was because my starter gearing was bound up and when I was turning it at the crank I was grinding the clutch. One of the teeth on the starter gear reduction thing was broke, so we got a gear from the original engine.

[HemiChallenger71]

That sounds cool, glad you could get it to work. Now we all know you can put a 300EX head on the 250's. Lets us know if the extra power is really worth the work.

[jeswinehart]

you sure been thru the mill with that machine bbechtel16 !

admire your determination man and great to hear ya got it going.

[bbechtel16]

Truthfully I had my doubts that we would ever get it running again.

Wouldn't you have to modify or replace the stock crank to take advantage of the TRX300's longer stroke? Could you swap cranks with the TRX300?

[bbechtel16]

Just tring to bring this thread back to attention. I am esp. interested in getting an answer to my last question. It would be awesome if I had my 2mm overbore high compression running with the 300's increased stroke. (Does some research and calculating...)

The new bore and stroke for my machine would be 76mmx65.5mm=297CC!!! But would it retain the 10.5:1 compression? Could I use a TRX300 crank? Could I have my crank stroked? I would definately upgrade to a 350X carb with that kind of displacement! New beefy cam and springs, aaawwww yeah! I'm all excited now; I wanna try this!

edit: Compared some part numbers on bike bandit and the head gaskets are the same number which I guess confirms what Jugernaut said about the heads being interchangeable?

[bbechtel16]

Wouldn't you also need a longer cam chain?

While we're on the subject of insane SX/ES mods (I know we should just buy a 350X but this is more fun), I was pondering today if anyone has and/or how much work do you think it would be to convert an SX/ES to manual clutch? I'm not sure of the specifics, but if I wanted to bother with it, I would figure out how the centrifugal clutch actuates the actual clutch, remove the centrifugal clutch, and fabricate some sort of way for a cable hookup to the right side case to work the clutch, and then run the cabling and put a clutch lever up at the bars. I don't think I want to try this but I'm hoping I give somebody a project idea here. It would be awesome if someone did this, they could put something up about it on the site and such, I would love to see a heavily pictured documentation of the project and stuff. Any takers?

[bebeav]

hey i thought i was the only one who tought about a 250sx with an manual clutch!!!!

i tried to find if it would work but too many prob.

i think the biggest prob remain in the side cover. I'll try to find all the link that i still know.

gotta search for my old post

ALP
Beav

[bbechtel16]

Come on, someone has to know something about this, eh?

[bbechtel16]

I'm going to beat this topic to death, again... I was pondering today, why not stick a trx300 motor in the sx (if it fits) and put the powroll piston in it for some 297cc 10.5:1 compression action? If only I knew it would work... Any ideas?

[250SX_rider]

MMm i'm not sure if the trx300 motor would fit in a SX...but the mods you wanna do are fu**ing' cool :o keep on thinking at that, and give us some news !

[250SX_rider]

Oh and if you didn't know, there is a big bore kit for the 250SX ( :-P ) that bumps displacement from 246cc to 300cc, find it there :

http://users.nlamerica.com/dixiebai/atv/html/sx1.html

but some guys tried to contact the dealer, i got no news... :evil:

Cya

[bbechtel16]

Oh and if you didn't know, there is a big bore kit for the 250SX ( :-P ) that bumps displacement from 246cc to 300cc, find it there :

http://users.nlamerica.com/dixiebai/atv/html/sx1.html

but some guys tried to contact the dealer, i got no news... :evil:

Cya

I too have viewed this website and heard of this beefy bore kit but as you mentioned when "people of the board" attempted to contact the company there was no response, so I'm figuring its a pretty much lost cause. BTW, thanks for the compliement above (I think) :twisted: Help me come up with yet more crazy ideas.

So does anyone know if I can run SX pistons in a fourtrax 300 motor properly? Also will the motor fit with little trouble?

[250SX_rider]

Did you put a K&N air filter in your SX ? ;)

[bbechtel16]

Did you put a K&N air filter in your SX ? ;)

Nope, was going to, had the filter picked out and a filtercharger to go along with it, even told the dealer to order it, but I called the next day and cancelled thinking "Why am I spending $73 on this when I found the same thing online for $38.19?" Then I realized the filtercharger isn't water resistant like outerwears (I'm bypassing the airbox). So now I'm going with an Uni dual stage (everyone claims foam is better anyway) and I'll get an outwears that will fit it. Unless I change my mind again, I sure hope not.

[atcmatt]

Im bringing this post back from the dead but i wanna know if anyone ever found a bigbore kit for the es/sx?

Thanks,

matt