Broken Power Valve (Lower Half MIA) GP1200R - Questions with Pics
pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Results 1 to 5 of 5
  1. #1
    Frequent Poster turbodriven's Avatar
    Join Date
    Sep 2006
    Location
    Orlando, FL
    Age
    47
    Posts
    169

    Broken Power Valve (Lower Half MIA) GP1200R - Questions with Pics

    I bought a GP1200R a few months ago, owner had tried rebuilding the carbs unsuccessfully. Found a bent throttle plate on the center carb and an overall dirty system but nothing crazy. So I did a full cleanup and rebuild and "synced fuel pumps", deleted the accelerator pump, removed chokes, installed primer pump and an overall re-jetted 110/125/1.5 for Riva Filters. Converted her to premix too. Cranked her up and after a few 15-20 second warmup the MAG and Center cylinders were warm but the PTO cylinder was cold. Checked for spark, it was good. Seemed wet inside the cylinder so I think I'm getting fuel. So I started investigating everything and when I opened up the power valve covers I found that it has the newer style (SBT?) pin retainers on the Power Valves. Great! But... the PTO PV was missing the M4x8mm hex bolt holding it to the shaft. Not great. Further investigation (pulled the head) showed that the lower half of the power valve was just gone. Broken off and MIA completely.

    Miraculously, the piston and cylinder look almost new. There is a tiny 0.5mmx2mm nick in the edge of the piston near the rear of the exhaust hole. And a "scratch?" in the sidewall of the piston near the same area (see pic #2 and #3).

    My question is...

    #1 What should be my concerns here? Just throw a new powervalve in and go? Pull the rest of the exhaust (stinger is already off)? I don't think any PV pieces could make it into the lower end of the block could they? Not wanting to pull any cylinders for no reason. 99% chance the pieces all got sucked out the exhaust right?
    #2 How does that "scratch" look to you??
    #3 Would this whole problem cause a cylinder to not fire (to be cold after a quick run-up off hose)? Just wondering if I need to look at the PTO carb (99% I rebuilt it perfectly) or whether this is likely what my problem was?
    Attached Images Attached Images

  2. #2
    Resident Guru kartracer41's Avatar
    Join Date
    Oct 2010
    Location
    lodi calif.
    Posts
    1,108

    Re: Broken Power Valve (Lower Half MIA) GP1200R - Questions with Pics

    Quote Originally Posted by turbodriven View Post
    I bought a GP1200R a few months ago, owner had tried rebuilding the carbs unsuccessfully. Found a bent throttle plate on the center carb and an overall dirty system but nothing crazy. So I did a full cleanup and rebuild and "synced fuel pumps", deleted the accelerator pump, removed chokes, installed primer pump and an overall re-jetted 110/125/1.5 for Riva Filters. Converted her to premix too. Cranked her up and after a few 15-20 second warmup the MAG and Center cylinders were warm but the PTO cylinder was cold. Checked for spark, it was good. Seemed wet inside the cylinder so I think I'm getting fuel. So I started investigating everything and when I opened up the power valve covers I found that it has the newer style (SBT?) pin retainers on the Power Valves. Great! But... the PTO PV was missing the M4x8mm hex bolt holding it to the shaft. Not great. Further investigation (pulled the head) showed that the lower half of the power valve was just gone. Broken off and MIA completely.

    Miraculously, the piston and cylinder look almost new. There is a tiny 0.5mmx2mm nick in the edge of the piston near the rear of the exhaust hole. And a "scratch?" in the sidewall of the piston near the same area (see pic #2 and #3).

    My question is...

    #1 What should be my concerns here? Just throw a new powervalve in and go? Pull the rest of the exhaust (stinger is already off)? I don't think any PV pieces could make it into the lower end of the block could they? Not wanting to pull any cylinders for no reason. 99% chance the pieces all got sucked out the exhaust right?
    #2 How does that "scratch" look to you??
    #3 Would this whole problem cause a cylinder to not fire (to be cold after a quick run-up off hose)? Just wondering if I need to look at the PTO carb (99% I rebuilt it perfectly) or whether this is likely what my problem was?
    pretty simple to take a compression test,it will tell you a lot.
    RGR Racing.com

  3. #3
    Frequent Poster turbodriven's Avatar
    Join Date
    Sep 2006
    Location
    Orlando, FL
    Age
    47
    Posts
    169

    Re: Broken Power Valve (Lower Half MIA) GP1200R - Questions with Pics

    Compression was 120/120/120 as I was rebuilding the carbs last week. Reeds looked good too. I'm assuming the Power Valve "incident" happened before I owned the ski? Cylinder appears clean, piston looks fairly clean. It's just incredibly odd to me that it could lose such a large chunk of metal and not cause any (or very little) damage. Should I buy a lottery ticket?

  4. #4
    PWCToday.com Is My Home Away From Home WFO Speedracer's Avatar
    Join Date
    Aug 2006
    Location
    Al-ugh-bam-ugh
    Posts
    26,184

    Re: Broken Power Valve (Lower Half MIA) GP1200R - Questions with Pics

    I have had two engines over the years break a power valve and damage nothing except the piston and rings, the rest were not so lucky.
    Last edited by WFO Speedracer; 11-03-2018 at 10:59 AM.
    Y'all know me, still the same O.G. but I been low-key
    hated on by most these &^$$@s with no cheese, no deals and no G's, no wheels and no keys, no boats, no snowmobiles, and no skis, mad at me cause I can finally afford to provide my family with groceries


  5. #5
    PWCToday.com Is My Home Away From Home Grumpy Old Guy's Avatar
    Join Date
    Dec 2003
    Location
    Sunny Fla
    Posts
    24,995

    Re: Broken Power Valve (Lower Half MIA) GP1200R - Questions with Pics

    I have seen a couple break off & go out the exhaust without any damage what so ever.

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