350x engine limits

[RamsesRibb]

I'm wondering what's been done on here as far as displacement with 350x engines.
I remember having a conversation with Curtis Sparks about my 350x when I was rebuilding it and he told me he could build it up to 565cc. He also said I was nuts to use that on a trike frame. LOL. But I guess in those days I could take the credit for that.

[murfman]

A 96mm piston will give you a 492 with the stock stroke crank(this is what I'm building). And a 535 with with a stroker crank. I have never heard of a 565. It must be a longer stroker crank then the 535 as I cant see getting much more than 96mm in the jug.

[GO OVRIT]

How well do the tranmissions hold up around 500cc's?

[RamsesRibb]

Don't know about trans, but I don't see the stock clutch holding up.

[Dirtcrasher]

Unless you never want to leave the ground, I can't see why people dump a couple grand into a 350X engine only to make it unreliable.

Unless it only gets out a couple times a year........

I guess I'm a rider, a jumper, a climber and a drag racer and the 500$ I have in mine make it plenty fast to do those things and keep it reliable.

Any faster and the frame and suspension cannot take the abuse I throw at it.

[murfman]

After talking to mike (Hurricane635) I went with the 96 mm piston, stock stroke and stock cam with a ported head, oversize valves, a 400EX Carb, headpipe and a TRX450 Muffler. I have less than 1000 in the upgrades, and with the stock cam and valve springs I cant see why it would be any less reliable than stock. I just wanted a torquey thumper that will hang with my buddies TRX450r. (At least enough to surprise him lol)

[Vealmonkey]

Ascott 500 head. Ascott 500 stock sleeve, Stock bore piston with stock compression. Stroked crank. Roller bearing cam. Plus other goodies, that I don't even know what they are! LOL Still a work in Progress. DirtCrasher Max-Gusseted frame. Jason Hall cr125 inverted front fork kit. HRE Custom rear swingarm. Jasons fork is here and assembled. HRE swinger is getting powdercoated and it will be on the way. Should be a "Wallet Breaker"! LOL Maybe I'll call it "Chapter 11" or maybe "Garage Queen"! LOL

[RamsesRibb]

Unless you never want to leave the ground, I can't see why people dump a couple grand into a 350X engine only to make it unreliable.

Unless it only gets out a couple times a year........

I guess I'm a rider, a jumper, a climber and a drag racer and the 500$ I have in mine make it plenty fast to do those things and keep it reliable.

Any faster and the frame and suspension cannot take the abuse I throw at it.
Well I've had the frame crack aXle carrier grenade, and a clutch wear out. I don't consider any of that major issues

[Dirtcrasher]

Well I've had the frame crack aXle carrier grenade, and a clutch wear out. I don't consider any of that major issues

And what do those 3 things have to do with what I said?? If your implying you have allot of motor work done to yours and haven't had many issues, then say so.

Who knows how you ride, how heavy you are, how much you use your clutch or how well you maintain your machine.

Plain and simple, once they have allot of engine work, they lose some reliability.

Not to mention that the faster you make it, the further you jump and there a heavy ATC to begin with.

[tecat-z]

And what do those 3 things have to do with what I said?? If your implying you have allot of motor work done to yours and haven't had many issues, then say so.

Who knows how you ride, how heavy you are, how much you use your clutch or how well you maintain your machine.

Plain and simple, once they have allot of engine work, they lose some reliability.

Not to mention that the faster you make it, the further you jump and there a heavy ATC to begin with.

I always felt that the 350x chassis and suspension was cut rate stuff. They designed such a wonderful engine in terms of torque and horsepower, that i've always felt 350x owners somehow got shortchanged. Back in 88, my good friend bought a 1 owner 86 that had MAYBE 2 tanks through it. Absolutely like new. I have felt this way ever since those days, when we jumped nearly everything. "I was a dirtbike rider" It was very clear the suspension was designed more for cruising than aggressive riding or jumping. Granted we were much lighter than today "prolly 160ish" but we had big stones too... I'll never forget the way that machine sounded, bone stock and factory fresh with the oem exhaust. It reminded me of a Volkswagon Beetle, cuz it had a sort of squeek to the exhaust when accelerating from low rpm in 2nd or 3rd, and than rolling strong into the throttle. It was very unique. Those engines really were great!

[RamsesRibb]

And what do those 3 things have to do with what I said?? If your implying you have allot of motor work done to yours and haven't had many issues, then say so.

Who knows how you ride, how heavy you are, how much you use your clutch or how well you maintain your machine.

Plain and simple, once they have allot of engine work, they lose some reliability.

Not to mention that the faster you make it, the further you jump and there a heavy ATC to begin with.
I'm just saying those were the only issues I had with the machine. As far as the other questions you ask. That was when i was younger. I weighed about 120 pounds and I was balls to the wall. I've raced local motocross on the machine and was the only ATV anywhere near to the dirtbikes laps. I was able to beat ATC250r's on the track. I don't remember details to the engine but I recall HP being in the 30's. I didn't have big bore or anything though. That was on my plate but I was injured in an unrelated incident and was unable to ride for a long time.

[murfman]

Who knows how you ride, how heavy you are, how much you use your clutch or how well you maintain your machine.

Plain and simple, once they have allot of engine work, they lose some reliability.


That simple statement can be said about any internal combustion engine. Hell, it can be said about anything... Your statement is not really saying anything. I'd put money on a modified 350X outlasting an equally modified 250 2 stroke.

[baycitysteve]

i've raced a 350x motor for many years and can show you a bunch of trophies from ice racing to tt to drag racing to a win at the silver dome when they raced the amateurs after the pros were done with the supercross track . you don't win if your not fast and reliable , the 350x just begs to be built faster , fresh oil and valve springs are the main key and a good clean air filter .. the only real week point is the clutch but that can be fixed pretty easy too .. my advise is to bore as big as possible put a big cam big valve springs in it and go spank everyone .. you don't really need to stroke them in less your gona be a tractor puller , trust me i had one , they don't rev fast enough .. look at the bore and stroke of all the new bikes small stroke + big bore = fast rev !! also a stroker crank will only last about a year of hard riding . just a big bore will last alot longer than a year ..

[Dirtcrasher]

That simple statement can be said about any internal combustion engine. Hell, it can be said about anything... Your statement is not really saying anything. I'd put money on a modified 350X outlasting an equally modified 250 2 stroke.

He's the one that posted a few simple issues that meant nothing, which I agree with.

However, it seems if you stroke these motors and bore them to the max, you lose some reliability and you have better have a serious clutch.

I'm not trying to argue, I'd love to have a faster 350X with more torque but I can't see it holding up. And, if you have seen my thread, I have done allot of upgrades to my 350X; Yet now I find myself over-jumping things because it gets there faster with more speed and torque.

I just feel that as far as in an ATC, making it a 450X or whatever, is only going to cause other breakage issues the way I ride.

The mods I've done to my 350X seem to suit it just fine with a fully gusseted frame and a 250R front end.

Just sharing my feelings.

If you want to go fast and tear up the world, do so with a 2 stroke designed for racing; I don't need to hit jumps any faster................

[baycitysteve]

are we talking about 350x frame limits or motor limits .. motor will hold most mods just fine ..

[sittinguy]

Don't forget the modified CDI, and heavy valve springs.

[baycitysteve]

this is my current set up i will race all winter .. 482 big bore 95mm 11 1/2 compression , poweroll ported head , tc hand ground huge cam , hd valve springs and ti valve retainers , 40mm electron carb bored to 41 1/2mm , hd clutch springs and the presure plates machined to except a extra metal and fiber plate , modded cdi , after market header cut at the collector and 2 1/4 pipe welded on at the collector back 28 inches to a rcm silencer (hahaha) slotted coil pickup advanced 3 degrees .. 15/28 gearing !! thump thump thumper !!! reliable ??? hell yes all day every day !! easy to start ?? hell no , not in the winter !!:beer

[sittinguy]

Holy Crap steve,, that sounds like a Beast!

Good for you. What is your top end speed with that gearing?

I have similar engine mods and 15/36 gearing and I get into the low 70mph's,,, with stock 22in rears.

[baycitysteve]

with 20 inch ice tires and a long strait around 100 at least thats what my buddy said on his sled next to me but its a lil hairy to look down and check speed . a few years back i raced a half mile ice track and you could actually draft on the straits and slingshot by but that was a lil hairy too !! i know for sure i can hit 100 on pavment , them studed tires weigh so much and rob alot of power !!