Results 1 to 8 of 8
  1. #1

    Join Date
    Oct 2006
    Location
    UNITED KINGDOM
    Posts
    160

    06 Gpr Modified Head

    I Have Been Given A So Called Modified Head.is There A Stock Measurement For The Head ,ie From The Face To Another Datum Point.i Am Assuming That The Normal Thing To Do Is To Skim The Head To Up The Compression And To Better The Squish.combustion Chambers Dont Look Modified.what Is The Normal Capacity Of The Stock Chamber??

    Washo6o4


  2. #2

    Join Date
    Jan 2006
    Location
    UK
    Posts
    202
    You need to measure the head capacity in CC ie use a burette, pipet or if really stuck a syringe (remember those Chemistry classes at school). stick a plug in the head and get it level and flat. Then fill it with either a light oil or water with a bit of washing up liquid in it (gets rid of the surface tension) untill it reaches the gasket face. The std head should measure something like 52cc and if you want 150psi then the head volume needs to be 45 or 46cc. When machining you need to get the squish clearance right.

    Alternatively I have a set of riva heads for a 1300, but one of them needs welding that I would sell if you fancy getting it fixed. Or send your OEM head to Jetshed in Sheffield.

  3. #3
    Hydrotoys's Avatar
    Join Date
    Jul 2005
    Location
    Mesa, AZ
    Posts
    16,712
    +1
    85
    Wash,
    I'm sorry I don't have any measurements for you, but I can give you a little advice about that head.

    Don't have it cut too thin, or the walls around the water jacket collapse. Once this happens, the tops of the cylinders get exposed to the combustion, and it eats up the top of the cylinder real nice.

    The black marks around the edge of the cylinder was from improper sealing caused by my stock 60T head warping up after 15 hours or so. This result was approx 165psi compression with gas valves and no porting. I was running 100oct at the time, hence the richness.
    http://www.hydrotoys.com/gpr/tuners/...r/DSC_4391.jpg
    Last edited by Hydrotoys; 11-04-2006 at 05:50 AM.

  4. #4

    Join Date
    Oct 2006
    Location
    UNITED KINGDOM
    Posts
    160

    modified gpr head

    Thanks For The Help Guys, It Appears That The Head Has Had 30 Thou Skimmed From The Face And No Mods To The Chamber. Can I Run This Head With A 3 Degree Key And Freeflow On Pump Gas If I Richen It Up With The Riva Efi Unit?

  5. #5

    Join Date
    Jan 2006
    Location
    UK
    Posts
    202
    Quote Originally Posted by washo6o4 View Post
    Thanks For The Help Guys, It Appears That The Head Has Had 30 Thou Skimmed From The Face And No Mods To The Chamber. Can I Run This Head With A 3 Degree Key And Freeflow On Pump Gas If I Richen It Up With The Riva Efi Unit?
    If the gasket face has been skimmed then the squished band needs to be machined as well, though you can close up on the stock clearance.

    You will need to run super unleaded for head and key jobby.

    I don't run free flow as it was too loud with the jet works mod below 3.5K

  6. #6
    2000 GPRXP 4tec shooter98xpl's Avatar
    Join Date
    Dec 2005
    Location
    Charleston SC
    Posts
    2,717
    +1
    3
    I had my stock head off my 06 motor milled by Jim1300. So far the head has been damn nice. The ski has better acceleration and the mid range punch is better now. Also, I had the head back in less than a week.
    SHOOTER

  7. #7
    Mongoose's Avatar
    Join Date
    Aug 2005
    Location
    Wales
    Posts
    665
    +1
    6
    That head has had 30 thou machined off the face.
    The squish band has been tightened, but the angle has not been altered.
    You can safely take 30 thou off without causing any weekness problems.
    Taking off the face only means you keep the variable chamber sizes of the oem head. 30 thou off with a stock head gasket gives abou 135-140 psi.(As we all know what happens to number 3 cyl when things are borderline, don't we!)
    How am I sure of all this?
    It was me who sold you the head.
    The specs were emailed to me, and they were followed to the letter.The specs came from a farly good 2 stroke tuner. You might have heard of him_LOWELL HORNING!!

  8. #8

    Join Date
    Oct 2006
    Location
    UNITED KINGDOM
    Posts
    160

    modified head

    thanks mongoose i have no doubt that the head is spot on.i needed to know whether it is ok to run it on pump gas with the advance key,freeflow efi and d plate.what set up did you use it with?have you gone over to different heads?

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Me vs. 06 GPR
    By 05RXPnoob in forum Sea Doo Open Discussion
    Replies: 15
    Last Post: 04-30-2006, 11:16 PM
  2. '06 RXP vs '06 GPR- Need Everyone's Opinion
    By Alex_GPR in forum 4-Tec Performance
    Replies: 19
    Last Post: 04-21-2006, 01:20 PM
  3. 06 GPR VS 06 RXP
    By GPR FL in forum Yamaha PWC Performance (2-stroke)
    Replies: 47
    Last Post: 04-21-2006, 09:17 AM
  4. PROJECT 06' GPR IS DONE............................
    By WATER WOODY in forum Yamaha PWC Performance (2-stroke)
    Replies: 24
    Last Post: 04-16-2006, 09:57 PM
  5. Stock 06 GPR Hitting 70.2 mph!!!!!
    By Drink My Dust in forum Yamaha PWC Performance (2-stroke)
    Replies: 11
    Last Post: 04-07-2006, 07:29 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •