Need Mechanics and Motor Builders Opinions


20 replies to this topic
  • ToXicD

Posted January 21, 2008 - 08:33 PM

#1

or anyone else with motor building experience. I got my 2001 xr650r motor in this week and pulled the head and cylinder off to do some inspecting i think that the head may be ported. I have never looked into a stock 650r head, but i would assume it is smooth like other factory intakes. My intake has swirl and i guess what you would call gouge marks like when you have port work done.

First question is can anyone measure their intake on their head and tell me what size it is so i can compare it to mine?? Also since the head seems to already be ported i am going to go ahead and put bigger valves in it. Now my question is can anyone tell me what i should go with as far as valves, springs and retainers?? I was thinking about going with the black coated stainless from XR's Only since they are cheaper then titanium, but as far as the springs go im not sure which to get?? I always assumed that titanium was better for performance, but also titanium is very brittle so i thought that they might crack sooner. Is there any truth to my assumption or am i way off here??

Also do the valves just seat against the aluminum cylinder head, or are there steel seats that are pressed in?? I would assume you would want a seat other then aluminum but i cannot find anything on valve seats for the xr650r :cool:

I would just like to hear from you guys what is better for reliability, steel or titanium and what the reasons are. I plan on ordering all my parts from XR's only so i would just like to hear what you guys would recommend. Also if there is someplace better or cheaper to order these kinds of parts from then please let me know so i can check them out also, thanks.

  • Krannie McKranface

Posted January 21, 2008 - 08:40 PM

#2

or anyone else with motor building experience. I got my 2001 xr650r motor in this week and pulled the head and cylinder off to do some inspecting i think that the head may be ported. I have never looked into a stock 650r head, but i would assume it is smooth like other factory intakes. My intake has swirl and i guess what you would call gouge marks like when you have port work done.

First question is can anyone measure their intake on their head and tell me what size it is so i can compare it to mine?? Also since the head seems to already be ported i am going to go ahead and put bigger valves in it. Now my question is can anyone tell me what i should go with as far as valves, springs and retainers?? I was thinking about going with the black coated stainless from XR's Only since they are cheaper then titanium, but as far as the springs go im not sure which to get?? I always assumed that titanium was better for performance, but also titanium is very brittle so i thought that they might crack sooner. Is there any truth to my assumption or am i way off here??

Also do the valves just seat against the aluminum cylinder head, or are there steel seats that are pressed in?? I would assume you would want a seat other then aluminum but i cannot find anything on valve seats for the xr650r :cool:

I would just like to hear from you guys what is better for reliability, steel or titanium and what the reasons are. I plan on ordering all my parts from XR's only so i would just like to hear what you guys would recommend. Also if there is someplace better or cheaper to order these kinds of parts from then please let me know so i can check them out also, thanks.


If the intake has anything more than casting clean-up markings, and is shiny, it is not stock.
What are your performance goals for the motor? How will it be used?

  • ToXicD

Posted January 21, 2008 - 09:23 PM

#3

the motor will be mainly used for riding at the dunes. i plan on going with a mid to high reving web camshaft for use with the hard faced rockers. I still would like the size of the factory intake so i can see how much it has been ported. I plan on running a 43mm carb so i am gonna measure it tomorrow and if it is smaller than 43mm i am gonna go ahead and bore it out some more anyways :cool:

  • cleonard

Posted January 21, 2008 - 09:45 PM

#4

There are a few guys here who have done things on the level that you are looking for. It is a small number with the expertise that you seek. Most of them are only here from time to time so keep posting. Most of us here don't do much engine mods beyond hi comp pistons and aftermarket cams.

The valves seats are steel inserts. They are not available as a replaceable part from Honda. I have had two replaced on my XR600. XR's Only made them and installed them.

If possible take some close up pictures of the intake. Most camera's have macro modes for that. It's how I made those photos of my rod small end. My camera isn't anything special. It's a point and shoot that I got for $125 a few years ago.

I've never looked at a 650R head close up, but every RFVC intake casting that I have seen looked pretty good from a flow perspective.

You might want to try calling XR's Only ask about what you want to do. They may have some direct experience. It's important to get to the correct person. I don't remember the guys name but it started with a K.

You could go to the technical question page at http://www.xrsonly.c...id=5&Itemid=285 and ask your question. I'm sure they like cool projects as much as the next gear head.

  • Thumpmeister

Posted January 22, 2008 - 12:41 AM

#5

If there are swirl marks, it sounds like there MIGHT have been some port work done. Was the motor taken apart previous to your owning it; does it have the stock head/base gasket?

I know a lot of the CRF guys have been going with the stainless valves because of reliability issues with the Ti valves. Kibblewhite makes the stainless valves as well, and I believe they make a larger size than stock.

If you want straight performance, go with Ti. If you want reliability and longevity go with stainless. I have seen guys w/ the Ti Valves and Springs, and made great power, but I don't know how long it would last.

Its been a while since my motor was apart, so I cannot remember what the seats look like, but I would assume they are of a harder material than the head.

You could also try contacting Precision Concepts to see what they might have to say. I'm sure they have worked on a few 650R's in their day...

  • ToXicD

Posted January 22, 2008 - 08:33 AM

#6

thanks guys for the imput. i am not sure if it has the stock base gasket as this is my first xr motor, but the gasket is metal if that means anything. i think i am gonna go with the stainless valves and probably springs also. i will try to post a pic later of the cylinder head intake to see if it looks like its been ported to you guys. i will call xr's only and see if they make the valve seats for the larger valves, thanks again.

  • martinfan30

Posted January 22, 2008 - 08:34 AM

#7

If you can post a pic of the ports and comb. chamber, it would help.

  • Kawabuggy

Posted January 22, 2008 - 09:30 AM

#8

In the automotive world, titanium valves are used only for their lighter weight. Meaning the valve action can be controlled with lighter springs, reduced chance of valve float, and less mass for the cam to move.

Since XR's were never meant to be twisted into high RPM's-my personal opinion is that titanium valves are over-kill for these motors.

Go with the stainless steel and you will be fine.

As suggested above, please try and take some clear pictures & post them so that the guru's here can what you are working with.

  • martinfan30

Posted January 22, 2008 - 09:59 AM

#9

In the automotive world, titanium valves are used only for their lighter weight. Meaning the valve action can be controlled with lighter springs, reduced chance of valve float, and less mass for the cam to move.

Since XR's were never meant to be twisted into high RPM's-my personal opinion is that titanium valves are over-kill for these motors.

Go with the stainless steel and you will be fine.

As suggested above, please try and take some clear pictures & post them so that the guru's here can what you are working with.



Just the guy I wanted to talk to. Hey KB, that 11:1 piston, you have to mix race fuel in or is 91 OK?

Sorry for the hijack...


+1 on stainless valves though.

  • HeadTrauma

Posted January 22, 2008 - 04:44 PM

#10

Titanium valves are realistically only used in maximum effort race engines that get torn down regularly.

Titanium forgings (like valves) are not brittle(similar physically to stainless steel), but they have a much shorter fatigue life than steel. When they get hammered and stretched out, they break. Ask the CRF guys about that. Below 10,000rpm, they would be an unnecessary risk and expense. You would also need to use a ductile iron or bronze seat with the Ti valves.

Regarding valve seats themselves, yes they are also steel. The blanks look like rings cut off of a steel tube. A good cylinder head shop should have or easily get seat blanks of any kind.

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  • weskc35k

Posted January 22, 2008 - 11:50 PM

#11

You probably wouldn't notice the difference between Ti and Stainless valves big fella actually neither would i i'd think,if you want it to rev quicker lighten your flywheel by a few ounces.

  • Denn10

Posted January 23, 2008 - 01:04 PM

#12

I think your covered on the valves and SS vs Ti stay with the SS. Hopefully you can get some pics of the ports soon.

  • ToXicD

Posted January 23, 2008 - 05:30 PM

#13

k guys got the pics, just trying to figure out how to post em

  • ToXicD

Posted January 23, 2008 - 05:41 PM

#14

Posted Image

  • ToXicD

Posted January 23, 2008 - 05:42 PM

#15

Posted Image

  • XR250rdr

Posted January 23, 2008 - 07:15 PM

#16

That doesnt look like any Honda factory port I've ever seen.

  • ToXicD

Posted January 23, 2008 - 07:19 PM

#17

yeah i didnt think so either, what do you guys think of the port work?? i guess thats a few hundred bucks i wont have to spend :cool:

  • Krannie McKranface

Posted January 23, 2008 - 07:51 PM

#18

That looks very un-stock. It looks like it might have even been a flow-test inspired port job. Very symetrical, and not too shiny.

  • martinfan30

Posted January 24, 2008 - 01:09 PM

#19

That looks very good. Not polished, not rough either. That will flow very very well! Who did it? Do you have a before pic? What were you'r expectations out of it?

  • ToXicD

Posted January 24, 2008 - 03:37 PM

#20

I have no idea who did it. Bought the motor a couple of weeks ago and noticed it when I was tearing it down.





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