pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Results 1 to 6 of 6
  1. #1
    Resident Guru bored&stroked's Avatar
    Join Date
    Dec 2006
    Location
    Mesa AZ
    Posts
    894

    61x cylinder max bore, conflicting info on website

    Hi Harry,

    I was reading threw the tech docs for the yamaha 701 on your site. When discussing 701 based big bore engines you state that 61x cylinders are too thin to take an 84mm bore and must be sleeved. In the F800 square nose buildup, you talk about boring a 61x cylinder to 84mm and that still allows another .5mm of overbore if needed in the future. You do also talk about rpm's in the F800 build, is that the governing factor in acceptable max bore diameter? Otherwise what changed to make you comfortable with an 84mm 61x cylinder?
    '90 Superjet: ported 760, dual 44's, B pipe, ADA head 190psi, TDR waterbox, hooker 10-16, sponsons. Girlfriends ride
    '94 Suuuperjet: 718cc, pro tec pipe, Groupk head 175psi w/protec girdle, protec ride plate, MSD coil, UMI grate, Roundnose pole -4", rev footholds, sweet green turf and wrap.
    '95 Raider 701: Fiberglass not SMC, Hydrotrailer hitch, ugly purple and yellow everywhere.

  2. #2
    Tech Guru Resident Guru
    Join Date
    Feb 2002
    Location
    Fort Mohave, AZ
    Age
    63
    Posts
    1,140

    Re: 61x cylinder max bore, conflicting info on website

    Bored,
    You bring up a good point. On our earlier big bore setups, most customers were building race boats intended for sustained high rpm use. The stock sleeves struggled to have the durability necessary for the intense loads of sustained high rpm use..... so we always installed the tougher (and slightly thicker) racing sleeves.
    However as the years went on, fewer and fewer customers were racing, and most were doing freestyle type riding and/or just lower stress recreational riding. For this less intense use, the stock sleeves bored to 84.0mm has very good long term durability. We do not recommend the 84mm boring of stock sleeves for race gas setups, nor for setups running the higher rpm dry pipe.
    Respectfully, Harry Klemm


    Quote Originally Posted by bored&stroked View Post
    Hi Harry,

    I was reading threw the tech docs for the yamaha 701 on your site. When discussing 701 based big bore engines you state that 61x cylinders are too thin to take an 84mm bore and must be sleeved. In the F800 square nose buildup, you talk about boring a 61x cylinder to 84mm and that still allows another .5mm of overbore if needed in the future. You do also talk about rpm's in the F800 build, is that the governing factor in acceptable max bore diameter? Otherwise what changed to make you comfortable with an 84mm 61x cylinder?
    Unless otherwise stated, responses to all forum posts are based on my personal experiences working within the PWC industry, and developing high performance PWCs since 1987.

    www.groupk.com

  3. #3
    PWCToday Newbie
    Join Date
    Jul 2016
    Location
    Brentwood ca
    Posts
    5

    Re: 61x cylinder max bore, conflicting info on website

    Would a pro tec exaust and 180 psi head and rev limiter removed get to high of rpms to make this okay to run at 84mm? Would it be better to play it safe at 83mm?

  4. #4
    I dream skis MTRHEAD's Avatar
    Join Date
    Nov 2003
    Location
    MotorCity
    Posts
    680

    Re: 61x cylinder max bore, conflicting info on website

    I ran a 84mm 61x cylinder with a dry pipe, 170-175 and it lasted for the few years I used it. No issue. With OEM electronics you not going to turn anymore than 7200-7300 if its massively modified. Your probably 6800-7000 best and it will last for a long time.

    180psi can be disastrous with the wrong "dry" pipe and oem electronics. Protec though doesn't make a drypipe

Thread Information

Users Browsing this Thread

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

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBadvanced CMPS v4.2.0