300EX Peak Power Output?

[rooster300ex]

What are ya'lls opinions on how much power you can get out of a 300ex engine with full out most power mods. Do ya'll think you could get a 300ex close to 35-40hp?

[xxnightraven73x]

easy fix unscrew the gas cap lift it up push the 300 out drive a 450 under it and screw the cap on heh heh :devil:

maybe 32-35 at rear wheels....not only is it a EX...its just a 300cc 4 stroke...i mean they have a hard time gettin 60 hp outta 450s....and those are the "best" 4 stroke motors out

[rooster300ex]

Originally posted by Honda86
maybe 32-35 at rear wheels....not only is it a EX...its just a 300cc 4 stroke...i mean they have a hard time gettin 60 hp outta 450s....and those are the "best" 4 stroke motors out

Thats not bad 35hp's out of a well built 300ex motor. Anybody think you could get alil more out of it.

[rooster300ex]

Originally posted by xxnightraven73x
easy fix unscrew the gas cap lift it up push the 300 out drive a 450 under it and screw the cap on heh heh :devil:

lol

[bradley300]

my 350 hit 32, i'm sure a 380, or a 416x could hit 40

[bwamos]

Aye.. it all depends on how much money and time you're willing to dump into port/flow and custom work.

I don't see the 300ex ever getting above 40hp naturally aspirated with gasoline. Spark plug is in a poor location.. hard to get an optimal burn.

[RUTHLESS]

EDITQJ
OFFENSIVE and RUDE

[rooster300ex]

What all would have to be done to a 300ex engine that would put out 30-40HP. You know how many cc's its capable of and everything else that it is capable of.

[bwamos]

330cc (0.240" overbore) w/ "professional" port & polish job tested on a flow bench, with oversized valves, agressive cam, 11:1 piston, high quality unbaffled properly tuned exhaust, 38mm carb, k&n filter, no-airbox lid, etc.. will get you about 30hp +/-

Well you could probably see 35hp out of it with mods maybe.

Max power well mod the motor as much as you can. Add nos and make turbo and you got a quad that will fly past the 450's BUT the turbo you would have to make cause i dont think any one has a kit for a 250ex and i dought you would go that far for power too.

People made home made turbo for less than $500 all ready.

The amount of cash it will cost to get 35hp out of a 300ex is alot. You should just drop a 400ex motor in their. You can get them cheep. I sold my Ex motor for $300 in realy good condition.

Originally posted by bradley300
my 350 hit 32, i'm sure a 380, or a 416x could hit 40

sparks makes a 416 for a 400ex i think that hits over 40hp.

[underpowered]

Originally posted by slow
sparks makes a 416 for a 400ex i think that hits over 40hp.

but he is talking about at 300ex, not a 400ex. i have seen 400cc+ kits for a 300ex/250x.

bradley is talking about his old GNCC 300ex witha GT thunder built 350cc big bore kit. My brother had it for a while and it was awesome. the fastest 300ex i have ridden. You could get 30-35 out of a 300. much more than that is pushing it.

Four stroke tech makes high cc stroker kits for the 300ex. Four stroke tech is the only place i seen that makes huge stroker/big bore kits for all quads.

[bradley300]

Originally posted by slow
sparks makes a 416 for a 400ex i think that hits over 40hp.

i'm talking about the 416 kit they build for a 250x;)

[bwamos]

Sparks and GT Thunder have bigger. ;)

40hp would be an EXTREMLY radical 300ex motor. It's like hitting 60hp+ on a stock bore 450r.

The 300ex's head jsut isn't "modern". The plug comes in from the side instead of the top like the 450's and 2-strokes have. You have an oversized lawnmower engine on the 300ex.. lol. It's just not made for HP like a crf250r or 450r is.

Originally posted by bradley300
i'm talking about the 416 kit they build for a 250x;)

Holly ****!!:eek2: That huge. :macho

Thats over 150cc gain. how is that possable? Does it come with a new cylinder?

i would love to see a 40 hp 300ex, i think that would sweet...i wonder whats the highest a 250ex or z250 could make?? lol

Originally posted by Honda86
i would love to see a 40 hp 300ex, i think that would sweet...i wonder whats the highest a 250ex or z250 could make?? lol

If you can make a 250x 416cc you could probably get other 250's to be that cc. 400ex with a 416 kit and built motor can hit over 40hp so the 250 wit hteh 416 kit would probably come close to that but the amount of cash it cost you could just sell the 250 and buy a 400ex for $1500

Originally posted by Honda86
i would love to see a 40 hp 300ex, i think that would sweet...i wonder whats the highest a 250ex or z250 could make?? lol

I seen one with over 50 hp. A hybrid 300ex with a yz426 motor.

[wilkin250r]

The easiest and most powerful modification would be to drop a 350X motor into it. It has slightly more potential than the 300EX, and is much easier than dropping in a 400EX or YZ426 motor, but that's not really the original question, is it?

Like bwamos was saying, the key is in the head. The intake is almost too small for the stock bore, let alone a large big bore/stroker. It needs to be ported and oversized valves stuffed in.

Even if you get the best port job in the world, there are other factors. When the spark plug comes in the side, your flame front starts on that side, so you don't get an efficient burn on the opposite side. A 2-stroke can be made with an offset combustion chamber, but a 4-stroke has valves, and relief pockets in the piston. There's just not much flexibility there. Even if you COULD get an offset combustion chamber, then you have one side of the piston heating up more, which will expand differently and distort the piston.

Anybody ever wonder why a 400EX built to a 465cc will make 45HP, but a 450 properly built can exceed 50? It's in the little details like this, they have already been figured out by the time the 450s came around.

[dork]

the largest i've seen were 425cc's or so. thats a 87mm bore and 71mm stroke. mickey dunlap said that the 425 kits didn't always run as strong as his 380/390 kits in the 300ex due to the longer stroke they had. the 250x/300ex motors can get away with their smaller ports due to their high rod/stroke ratio which results in slower piston speeds. but when they're stroked, piston speed increases and the engine will need larger ports and valves to keep up with it. so the big stroker motors quickly run out of breath before the bore kits do. i built a 380 for my friend and would estimate power around 35-38hp at the wheels. it revs out to 9200rpm and is 11:1. i think a 12 or 13:1 380/390 with more aggressive head work could definitely crest 40hp. the 400ex's have the same problem too when built big, not enough valve area for the cc and old chamber designs. either way, they both run good for old air cooled motors.:D

[2muchquad]

i built a 380 for my friend and would estimate power around 35-38hp at the wheels. it revs out to 9200rpm and is 11:1. i think a 12 or 13:1 380/390 with more aggressive head work could definitely crest 40hp

I agree with Dork,he gave me valuable info when i was building my 385 300ex.The biggest gain for me besides the displacement was going to a fcr carb,period.I thought it ran good with the 400ex carb i had on but theres no comparison.Throttle response is right now,i couldnt believe it.While i dont have any hp figures i do know that i had it out riding with a 416ex with a pipe and i was climbing the same hills with more gusto than it did but i didnt race him though.I had a big oil cooler and a fan on it to keep it cool because i was running high compression.

[2muchquad]

Im pretty sure i read somewhere that a stock 300ex with the choked stock exhaust system made 36hp,thats almost 4 hp down from a piped 4 fiddy,not bad.:D :D :eek2: :eek2:

[elementryder]

i talked to tom carlson and he said to expect about 32 hp out of one of his 298 engines max

[2muchquad]

i talked to tom carlson and he said to expect about 32 hp out of one of his 298 engines max

Who does he think he is?Is he an authority or 300ex guru?..j/k:D

[elementryder]

no he just told me thats about what my engine will put out after i send it to him