Anyone run a fathead?


14 replies to this topic
  • DesertCR

Posted January 13, 2014 - 08:24 PM

#1

I bought mine used for my 03 cr125 so I never received instructions.  Well after installing it I had coolant coming up thru the studs/nuts on the head.  I think Im supposed to use the metal head gasket along with the rubber orings that come with the fathead?  I just used the orings figuring thats how it was supposed to be, kind of like most 2 strokes (yz,rm,kx, etc).  Btw if anyone has one, I need the torque specs. I've emailed Lukesracing (they sell them) but the sooner the better, thanks.



  • silver_fox

Posted January 14, 2014 - 12:36 PM

#2

Maybe it's warped? Do you know why the previous owner sold it?



  • DesertCR

Posted January 17, 2014 - 11:14 AM

#3

Well I finally got ahold of them and they said I have to run the acorn nuts as they seal the coolant in, kinda weird.  Im running the stock Honda nuts, Yamaha or Suzuki ones will work.  So if you have one of these heads make sure you run the copper washer and acorn nuts.



  • hawaiidirtrider

Posted January 17, 2014 - 02:11 PM

#4

Well I finally got ahold of them and they said I have to run the acorn nuts as they seal the coolant in, kinda weird.  Im running the stock Honda nuts, Yamaha or Suzuki ones will work.  So if you have one of these heads make sure you run the copper washer and acorn nuts.

Wow really? I don't remember now if I have acorn nuts or not..or if they even came with them. I have to look at my bike now.



  • adam8781

Posted January 17, 2014 - 02:15 PM

#5

having you stock head setup by rb designs is far superior to any after market head



  • hawaiidirtrider

Posted January 17, 2014 - 07:11 PM

#6

having you stock head setup by rb designs is far superior to any after market head

Why? ..how do you know? Have you tried a phathead cool head? Does rb designs have a higher volume of coolant in the head that lowers temps?

 

Can you change out different domes for different applications? Have you tried different high compression domes if you have tried aftermarket cool heads like from esr, vhm, prodesign cool etc.

 

http://www.eddie-san.../cr250 dome.htm

 

http://www.lukesraci...r/phathead.html

 

http://www.prodesign..._cool_heads.htm

 

http://www.vhm.nl/?navi=cylinderheads

 

PD5.jpg

 

If you have fine.. but I somehow kind of doubt it.


Edited by hawaiidirtrider, January 17, 2014 - 07:13 PM.


  • DesertCR

Posted January 17, 2014 - 07:23 PM

#7

I will do a RB head in the future also, just wanted to give one of these a try first.  Just from a quick lap in the back yard I can tell the bike had noticeable more bottom. Should have it back together next week.



  • hawaiidirtrider

Posted January 17, 2014 - 07:32 PM

#8

Do you know what dome you have for your bike? That's a lot cheaper and you can change for your needs for cheap.. plus if you don't like it you can go back easily. .plus the larger volume of coolant in the head is a distinct advantage for having your bike run cooler. It was the main reason I got my phathead . I wanted improved cooling and it helped. There are other companies too that are similar in design. I'd imagine those would be good also.



  • DesertCR

Posted January 17, 2014 - 07:59 PM

#9

I have 3 domes, all except the closest to stock.  If I can get rid of the coolant leak, I will def keep it on the bike.



  • hawaiidirtrider

Posted January 17, 2014 - 10:02 PM

#10

I have 3 domes, all except the closest to stock.  If I can get rid of the coolant leak, I will def keep it on the bike.

That's unusual. Usually it's been sold as close to stock, high compression (race gas) and a low compression for altitude. I guess some models come with more domes. I bought mine new with the close to stock and the high comp. dome. I wanted cool first and figured I would want to play around later and give my bike a little more power. You remind me. I better order some o rings from lukes for when I want to change domes later.


Edited by hawaiidirtrider, January 17, 2014 - 10:06 PM.


  • NicholasA

Posted January 17, 2014 - 11:29 PM

#11

Yea you still have to run the normal head gasket under the O-rings. Btw I have a phathead with a brand new stock honda dome and O-rings that came off a 2004 cr125 I don't know what other years it will fit but I have no use for it anymore and want to sell it if anyone on here is interested pm me an offer ImageUploadedByThumper Talk1390030132.370799.jpg

Edited by NicholasA, January 17, 2014 - 11:31 PM.


  • hawaiidirtrider

Posted January 17, 2014 - 11:54 PM

#12

Yea you still have to run the normal head gasket under the O-rings. Btw I have a phathead with a brand new stock honda dome and O-rings that came off a 2004 cr125 I don't know what other years it will fit but I have no use for it anymore and want to sell it if anyone on here is interested pm me an offer attachicon.gifImageUploadedByThumper Talk1390030132.370799.jpg

Maybe it's different for a 250 than a 125. I didn't put a headgasket for my cr 250.. It's been so long. I think it's best to check with phathead to make sure of the right gasket. I distinctly remember that I couldn't use the stock 250 honda head gasket though. 


Edited by hawaiidirtrider, January 17, 2014 - 11:55 PM.


  • DesertCR

Posted January 18, 2014 - 09:42 AM

#13

I called them directly and they said not to use the stock gasket...? I know the 04 125 is slightly different, not sure on the cr250.   Btw when purchasing these heads new you get your choice of two domes but I also bought a 3rd dome after the fact. 



  • NicholasA

Posted January 18, 2014 - 09:44 AM

#14

Maybe it's different for a 250 than a 125. I didn't put a headgasket for my cr 250.. It's been so long. I think it's best to check with phathead to make sure of the right gasket. I distinctly remember that I couldn't use the stock 250 honda head gasket though.

Yep you're right, just checked on their website and at the end of the first paragraph under the picture it says phatheads are designed to run O-rings in place of a head gasket. Here is the link to the Luke's racing website where I got my info from. http://www.lukesraci...r/phathead.html

  • kauko40

Posted January 24, 2014 - 01:13 PM

#15

Yea you still have to run the normal head gasket under the O-rings. Btw I have a phathead with a brand new stock honda dome and O-rings that came off a 2004 cr125 I don't know what other years it will fit but I have no use for it anymore and want to sell it if anyone on here is interested pm me an offer attachicon.gifImageUploadedByThumper Talk1390030132.370799.jpg

definately no head gasket, only the O-rings







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