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Old 09-24-2005, 04:27 PM   #1
creeper OP
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A look at a '05 Honda XR650R Cylinder Head

I recently received a 2005 Honda XR650R cylinder head for inspection and possible repair and improvement... and thought some of our XR owners out there, and maybe others, might be interested in what I've found.

This head belongs to a gent from Idaho. His concern was that this new bike does not perform like his old bike, so he sent me the head to have a lookie see.

Here is the head and valve train parts after cleaning, glass beading and cleaning again. After cleaning, I took measurements of valve to guide clearance, valve and seat runout, valve stem protrusion and spring pressure at installed height.



Valve to guide was IN. .001" & EX. .0017".
Spring pressure was matching within 6%.
Stem protrusion was within .005" intake for intake and .003" exhaust for exhaust.
Valve runout was less than .002 max. and averaged .0013".
Valve seat runout was not so good at and average of .002" for one each intake and exhaust and .0045" for the remaining two... both of which failed a loaded wet test and unloaded light test. So we had a bit of leakage there.
All the valve seat contact angles were what I felt to be a bit on the wide side, which may have contributed to the leakage.
Also, one of the intake valves, the one with the better contact seal had a substantial amount of soft carbon deposits on the port side of the valve head, indicating a possible guide seal fault.

All in all, not too bad.

The ports themselves look to have pretty effective shapes overall. A little rough, but that’s to be expected in a production head.

An exhaust port view. Very nice. Both exhaust ports looked like this at the port seat junction, pretty much all the way 'round. Only a small amount of clean-up required here.


And a view up the intake ports. Not so nice. The seat is extending into the port over .050" on the "long side" of the port. That has got to be blended in.


On the short side, a machined surface makes for a less than smooth "short side" of the port. A virtual cliff for the flow to jump off of and become turbulent. A bit of radius work here.


So, that's where we're at. The valves are in nice shape, no serious pitting or cupping and will be reused as per the owner. The springs are fine, as are the guides.


I will be recutting the seats just enough to make them concentric. As the valve faces are in such nice shape, rather than re-machine the faces, I'll lightly lap them in to the fresh cut seats.

On the ports, I'll be working mostly on the intake side, blending the seats in on the long side of the ports and radius the "cliff" a bit on the short side. I can't make it text book perfect as the casting wall thickness in that area is not real thick to begin with.
From past experience, I can say that a 4% - 7% intake flow improvement should be realized on the intake side with a negligible loss in velocity.
I'll buzz out some of the "bigger" lumps in the exhaust ports, mostly because that's what I do... but I doubt there is any room for improvement with out a loss in velocity.

To be honest, I don't see anything in the head alone that could cause the noticeable differences in throttle response and power the owner is claiming. It's not perfect by any means, but there's nothing really terrible... his previous 2000 XR must have been a real storm trooper.


I'll post again when I'm close to finished with the head... ciao.

C
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Old 09-24-2005, 08:40 PM   #2
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Old 09-24-2005, 08:49 PM   #3
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Chris,

Please remember when working on Jap heads;

あまりを取ることの注意深い



CC
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Old 09-24-2005, 08:57 PM   #4
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Quote:
Originally Posted by ChrisC
Chris,

Please remember when working on Jap heads;

あまりを取ることの注意深い



CC
"Taking remainder it is careful"... roger that.
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Old 09-24-2005, 09:01 PM   #5
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Quote:
Originally Posted by creeper
"Taking remainder it is careful"... roger that.
I love these translator engines.....Google says that's "don't take too much off"

Close enuf
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Old 09-24-2005, 09:09 PM   #6
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Quote:
Originally Posted by ChrisC
I love these translator engines.....Google says that's "don't take too much off"

Close enuf

I used World Lingo. We would both be in a world of hurt in Japan.
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Old 09-24-2005, 09:16 PM   #7
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Gee, this is fun....

私の毛深いろばのひびを舐めなさい

Now back to the cylinder head stuff, OK?
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Old 09-24-2005, 09:18 PM   #8
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Quote:
Originally Posted by ChrisC
Gee, this is fun....

私の毛深いろばのひびを舐めなさい

Now back to the cylinder head stuff, OK?

...
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Old 09-24-2005, 09:56 PM   #9
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Quote:
Originally Posted by ChrisC
Gee, this is fun....

私の毛深いろばのひびを舐めなさい

Now back to the cylinder head stuff, OK?
And I actually spent the time to translate that, damn! No fortune cookie there. lol
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Old 09-24-2005, 10:45 PM   #10
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And I actually spent the time to translate that, damn! No fortune cookie there. lol
Много удача... меньший cookie.
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Old 09-24-2005, 11:54 PM   #11
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Много удача... меньший cookie.
Much luck... smaller cookie. haha three can play at that game. :)
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Old 09-25-2005, 07:34 PM   #12
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i read a ebay post by scott summers selling one of his 650r's , he said the engine was stock except for the head which was custom as a gift from honda, he said it had better low end response, my guess smaller ports?

I'm not suure if this was a race or practice bike, but he said he did ride it a bunch.
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Old 09-25-2005, 08:08 PM   #13
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Works of art.
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Old 09-25-2005, 08:58 PM   #14
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Old 09-25-2005, 11:32 PM   #15
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Quote:
Originally Posted by HighwayChile
i read a ebay post by scott summers selling one of his 650r's , he said the engine was stock except for the head which was custom as a gift from honda, he said it had better low end response, my guess smaller ports?

I'm not suure if this was a race or practice bike, but he said he did ride it a bunch.
That would be a good guess. A well designed port doesn't have to have a large cross-section.
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