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Krannie McKranface

XR650R headers: any equal length ones?

14 posts in this topic

I've seen some in pictures, where the left and right header exhaust port pieces are of equal length, but most are not.

Also, the stock header seems to drop down to a restrictive size very quickly. This has to hurt......

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There is a UK header that is equal length. I think it might be an "Arrow" brand header. A tube goes around each side of the cylinder. It might get in the way of a desert tank, as the left side of desert tanks drop down and hug the cylinder.

Drawing back from my vehicle design classes, unequal length headers give you multiple harmonics which broaden the power band. Equal length headers tune for a narrower powerband as there are less harmonics, but a strong pulse at the sweet spot. Some older Lemans cars used to use this on both the intake and exhaust side. Now they have different tricks for intakes.

The factory tube diameter reduction is actually factory tuning for low end torque increase. It only hurts on the top end of the RPM band where the stock cam is already done. If you want to improve, get the aftermarket cam and header at the same time.

If you want to make it suck compared to stock/uncorked, get a big cam with factory header or big header with factory cam. Either way, you lose torque on the bottom and don't gain much on top.

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I got a stage 2 with the stock headers doesn't suck at all goes real good actually, the power is great off idle to about 6 and a half grand ,still hits the rev limiter in top gear with 15/46 though.

You are spot on about the unequal length headers though, one pulse helps scavenge the next so to speak.

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Thanks for all the great repsonses. I understand more now. I think that having at least one longer header pipe would be an advantage for the tuning I am seeking.

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I believe Doma, Moriwaki and Remus are equal length tubes. Why do most automotive race teams strive to have all the head tubes exactly the same length? Does it still apply to a one lunger four valve duel head pipe? I understand the effect of scavenging of one cylinder to the next at the header collector.

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wow this place is just a wealth of knowledge. always amazes me that sure was a nice looking pipe from krummer i see they even got one for my bike xr600l wonder how much that 129.00 was that lira?? compared to dollars

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wow this place is just a wealth of knowledge. always amazes me that sure was a nice looking pipe from krummer i see they even got one for my bike xr600l wonder how much that 129.00 was that lira?? compared to dollars

A Euro is about $ 1.50 dollars.

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A Euro is about $ 1.50 dollars.

1 euro is about 1.3 Dollars I think.

That's +- 167 dollar for the ABP-racing headers.

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1 euro is about 1.3 Dollars I think.

That's +- 167 dollar for the ABP-racing headers.

It was about that. However, the dollar is plummeting. This morning a euro is at about $1.47

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