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RYDRZ

BIG BORE ENGINE KITS

13 posts in this topic

All brands & all sizes

What combo have you tried ?

or have got & great value ? ,

& What Tuning tips for bigbore kits?

did you fitt it or you paid to have it fitted & where??

Me i dont just want a small upgrade

For my

06' WR450F ,

Small kit

( Like 468cc or 478cc )

i want The biggest WR 500cc kit

Im greedy ;)

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So what say you guys & girls

I know im not the only power greedy mofo

& im sure there maybe bigger than 500cc kits out there for our bikes

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The real question is...........why?

 

It's already a very chuggy motor...........

 

....and you won't make any more power, you will just move it down in rpms....

 

...and then it will vibrate more....

 

There is a reason why no manf ever makes an *largely* over-square motor.

Edited by Kah Ran Nee

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Wouldn't be my cup of tea, I don't like vibrations.

It's not already oversquare stock?

Might not make more power but surely should make more torque.

Edited by cracker please

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Yup.

Less power

Same weight

Terrible suspension.

It's a great plan.

It's hard to convey sarcasm in text.

But seriously displacement isn't everything.

Port your head and mess with cams before you do a BBK OP.

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There is a reason why no manf ever makes an *largely* over-square motor.

 

 Would you say the 350 KTM sort of falls into that category?

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Beta makes some crazy stuff too if you look up some of their specs.

Like the 480 is 100mm bore x 60.8 stroke. 

And they got a 390 that's 88 x 63.4

I know they're not a major brand, just found it kind of interesting.  It would be cool to test some of them out.

Looks like the 4 valve YZs are 97 x 60.8.  That's more oversquare than a 488 WR.  I guess the HP wouldn't be there when the head isn't made for a big ass piston like that though.

Edited by cracker please

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Kah Ran Nee, on 24 Nov 2014 - 5:47 PM, said:

Yup.

Less power

Same weight

Terrible suspension.

It's a great plan.

Surely your joking right? Sometimes its hard to tell!

 

Bundy

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There is a reason why no manf ever makes an *largely* over-square motor.

 

At 95.0 × 63.4, the WR450 is already 50% over square.  The 302 Chevy small block, built to run well past 7000, is only 33% over square.  The current YZ450 is 97 x 60.8, which makes it 60% over square. With a 3mm overbore, the WR would be less than that at 54.5% over.

 

These numbers are typical of modern high performance motorcycle engines, and were not long ago considered extremely radical.  The practice was originated by Ducati in an effort to gain power over the two strokes they raced with in Europe by the only means left to them; extremely high RPM.  The trend is toward even more over square designs.

 

So who is it that hasn't built a largely over square engine yet?

 

 

i want The biggest WR 500cc kit

Im greedy ;)

 

Yes, you are, but so are the people who make the stuff you want.  First, do the math.  A 488cc kit will increase displacement by less than 9%.  All other things being equal (which they aren't), you could imagine that a 9% increase in torque would follow, but it's not a truly linear relationship, so expect more like 6 or 7.  Since the stone stock '06 makes about 33 HP on a good day, that brings you up to around 35ish.  Not a lot of bang for the buck.

 

To go bigger, which can be done only by a stroker crank, you'll pay almost twice what the bore kit cost for a really good one, and that would bump displacement on a stock engine to 470cc for an increase of less than 5%.  See where this is going?

 

The 488 kit is a 3mm overbore, so the result of using both would be about 509cc, an increase of roughly 13%, probably a little more torque in the lower rev ranges, and possibly 4 whole HP, all for about $1200 American or more once the balance job is added in.  You can get that kind of gain for a whole lot less in other ways.

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You'd be better off spending your money on suspension improvements.   If the engine is in need of a rebuild, go with one of the small big bore kits, like Cylinder Works , as they are no more expensive than the standard bore.  When I did one on a 250 I had to go to a bigger pilot jet and a smaller main jet, your results may be different.  

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