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goodies for a YZ250f

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I'm not sure to follow you. I can't be way off saying that more compression leads to more heat can I? This is just laws of physics. Then I can't be way off saying that overheat is not really good...

What I mean is that the YZ250f engine revs high enough, has already what? 12.5 comp ratio, low amounts of oil considering the performance and heats way enough as is... I'll buy a 450f before buying a high comp piston...

Just my humble opinion.

Do you guys consider the cooling system of the YZF250 can handle a high comp piston easily?

you still never explained how a high comp. piston creates more heat

i dont see how adding more compression will add more heat to the engine

all its going to do is compress more air, how will that cause more heat?

maybe im missing something here, but i cant seem to think how its going to produce more heat. am i right or is there something im missing here?

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Want a good bike to rape your friends on the track? DEFINATELY get your suspension done, get the proper tires for your conditions, jet the bike spot on ( you may have to get a shop to do it if your not an ace), get some nice handle bars, set everything up on the bike to fit your style then go nuts. Trust me, you don't need all that junk you listed, I can rape people with $5000 worth of performance mods on my very stock but perfectly set up motor.

Intermediates around here can race and win on a 250f in the 450f intermediate class, its 90% rider, 9% bike set up, 1% bike...well not really, but you get my point.

Spend your spare money on a quality helmet, neck roll, chest protector, knee braces, boots and some slick looking gear.

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I'm not sure to follow you. I can't be way off saying that more compression leads to more heat can I? This is just laws of physics. Then I can't be way off saying that overheat is not really good...

What I mean is that the YZ250f engine revs high enough, has already what? 12.5 comp ratio, low amounts of oil considering the performance and heats way enough as is... I'll buy a 450f before buying a high comp piston...

Just my humble opinion.

Do you guys consider the cooling system of the YZF250 can handle a high comp piston easily?

yes, the little more compression will make a tad more heat, but my engine temps have stayed relatively the same. have i EVER boiled over.....no.

yes, it can handle a HC piston no problem. and for the performance gains i got, it was well worth the extra degree, if that.

you still never explained how a high comp. piston creates more heat

i dont see how adding more compression will add more heat to the engine

all its going to do is compress more air, how will that cause more heat?

maybe im missing something here, but i cant seem to think how its going to produce more heat. am i right or is there something im missing here?

ever tried the trick where you put a small peice of Kleenex(the lesser brand will also work) at the bottom of a tall glass chamber, and get a "piston", with rubber rings and a handle on top?

well you push the "piston" down the glass tube as hard as you can and the peice of tissue lights on fire.

why? becuase when air compress's it makes a hell of alot of heat :thumbsup: the air molucules rub together so fast, that it creates friction. pretty cool huh?

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yes, the little more compression will make a tad more heat, but my engine temps have stayed relatively the same. have i EVER boiled over.....no.

yes, it can handle a HC piston no problem. and for the performance gains i got, it was well worth the extra degree, if that.

ever tried the trick where you put a small peice of Kleenex(the lesser brand will also work) at the bottom of a tall glass chamber, and get a "piston", with rubber rings and a handle on top?

well you push the "piston" down the glass tube as hard as you can and the peice of tissue lights on fire.

why? becuase when air compress's it makes a hell of alot of heat :thumbsup: the air molucules rub together so fast, that it creates friction. pretty cool huh?

Another very good example: any idea how a diesel engine works without a spark plug? It fires only by the action of fuel compression. In a diesel engine, you reach the treshold in terms of energy needed for combustion to trigger by itself by compressing the fuel...

Basically, compress any gaz and heat will be generated for the reason mention by Way Fast Whitey.

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I looked at the Hot Cams website and they say they will improve top end. I don't need that. I need more bottom on the 250 because that's what I'm gonna miss while riding ithe 250 instead of the 426.

I guess then that a high comp piston will be better. The high comp generates more torque does it?

Thanks

Mathieu

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ok thanks guys

now i understand how more compression will make more heat

im gonna try that thing with the glass also....lol

:thumbsup:

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Another very good example: any idea how a diesel engine works without a spark plug? It fires only by the action of fuel compression. In a diesel engine, you reach the treshold in terms of energy needed for combustion to trigger by itself by compressing the fuel...

Basically, compress any gaz and heat will be generated for the reason mention by Way Fast Whitey.

yes, the heat of compression ignites the air/fuel mix. heres a good one, have any idea what octance diesel is rated at?

I guess than that a high comp piston will be better. The high comp generates more torque does it?

yes, a hella of a lot more torque, the YZ 250F, in stock form has very little low end grunt, with the HC piston it got alot more, i mean alot. and the 1 ring design by Wiseco hasn't let me down yet. (knock on wood, keep my fingers crossed, etc.) i will be replacing the ring before selling though :thumbsup:

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Can you just replace the piston with a high comp version and keep the jetting stock?

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yes, the heat of compression ignites the air/fuel mix. heres a good one, have any idea what octance diesel is rated at?

:applause: Since diesel is way less refined than ordinary fuel, then I guess there is way more octane and other low explosive types of molecules in there but I don't know how much at all :thumbsup: .

Tell us what the octane rate is. :ride:

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Can you just replace the piston with a high comp version and keep the jetting stock?

Um... it would probably be alittle too rich. But it is a good time too learn jetting. I think every MXer and trail rider should learn how to jet.

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Despite what most people say, FMF makes a very good pipe for that bike. It improves the low end quite a bit. If you get the full system, it comes with a jetting kit also. You could also get a power now. I like mine. Triple clampls also help the feel of the bike.

I beleive the hot cams can be adjusted a little for where you want to add power, but it's pretty complex. I could be wrong on that though.

If you ride hard, you will ruin the stock rims and spokes. Might want to save up for after market ones.

I've never liked renthal chain and sprokets, you can get a lot more wear out of other brands.

Another thing to think about is the air filter. Twin Air makes a different cage and filter that I would reccomend.

Accelerator pumps can help also.

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Um... it would probably be alittle too rich. But it is a good time too learn jetting. I think every MXer and trail rider should learn how to jet.

I'm not too bad at jetting... and I like to learn. I just wanted to know how the high comp affects jetting and why.

Thanks

Math

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Get your suspension set-up before you go blowing huge amounts of cash on a 1-3 HP increase with a pipe. Suspension will actually make you faster.

Yes. Best money spent on an mxer, w/o a doubt. Should be done before anything else, aside from maybe rebuilding a tired motor....

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Oh, and someone mentioned it, Renthal sprockets did not last long on mine at all. I got much more wear out of Tag sprockets and a Regina top of the line non o-ring chain. You'll lose a tiny bit of HP with an o-ring chain. Little more drag.

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Oh, and someone mentioned it, Renthal sprockets did not last long on mine at all. I got much more wear out of Tag sprockets and a Regina top of the line non o-ring chain. You'll lose a tiny bit of HP with an o-ring chain. Little more drag.

yes, but my ironman will outlast anything :thumbsup:

Yes. Best money spent on an mxer, w/o a doubt. Should be done before anything else, aside from maybe rebuilding a tired motor....

AGREED, i wish i would hve set-up my suspension before buying a pipe, the power is nothing if you can't put it to the ground :ride:

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AGREED, i wish i would hve set-up my suspension before buying a pipe, the power is nothing if you can't put it to the ground :thumbsup:

Understood. I promise that the first thing I do is to have my suspension dialed up. Are you guys talking about full after market suspension? Revalving of the stock suspension? Tell me a little more. I'm a real suspension newbie.

Thanks

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Understood. I promise that the first thing I do is to have my suspension dialed up. Are you guys talking about full after market suspension? Revalving of the stock suspension? Tell me a little more. I'm a real suspension newbie.

Thanks

just do this, and if you need new springs......get them!

set the sag, and free sag.

you do this by sitting on the bike and measureing how much it moves when you sit on it. if the shock rates are similair(between mine and yours), you'll need a new spring if you want to have the proper rider sag and free sag.

when you sit on the bike, in a normal position, you want between 110 and 100 mm's of travel.

"rider" sag = 100-110 mm

when you get off the bike, you want it to sag 30mm from its full upright position.

"free" sag = 30mm

if its more/less, you need to change sprinds accordingly

you can stiffin the whole stroke of the forks by turning the set screw in the bottom of the fork. also, becuase your a bigger guy(i am too) you might want to add 10cc of fork fluid or so to help your forks bottoming resistance.

i am no expert, i just did the above(except buying a new spring) and its now a whole different animal.

good luck :thumbsup:

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I can't believe no one has told this guy to get a new graphics kit. Everyone knows a new graphics kit will make your bike go faster. and make sure you spend at least 60 on pre-printed numbers. If you dont you will crash.

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what kind of suspention adjusting should you do if you dont weigh alot and arent every tall?

me ofcourse.. you cant have proper sag because your short. therefor you cant reach to plant a foot.

also i weigh about 120 without gear. and im about 5'6 with boots on :thumbsup:

what kind of setup should i do.

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