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  1. #1

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    Do I need to replace this cylinder?

    I recently had an incident while boating and now I need a new piston and I'm not sure about a cylinder, but I think I need to replace that as well. I'm not sure exactly what the underlying problem is, but I think it might be that I was low on gas and went into a spin because thats when the engine died (in other words running lean?). I have an XR1800 and I understand the gp1200r has the same engine. I am quite naive when it comes to this so please bear with me. Pictures of the cylinder and piston are attached.Click image for larger version. 

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    Thanks for any and all help!


  2. #2
    WATER WOODY's Avatar
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    Whole motor has been hot/lean. Look at the rod color. Also, i only see 1 shim on the big end of the rod. How many hours on the motor? I can see part of #2 piston which is lean. So far, a carb rebuild/rejet. I cant tell from the pics but are all 3 cylinders sleeved?

  3. #3
    L Carlson's Avatar
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    Looks like an SBT Motor

  4. #4

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    Quote Originally Posted by WATER WOODY View Post
    Whole motor has been hot/lean. Look at the rod color. Also, i only see 1 shim on the big end of the rod. How many hours on the motor? I can see part of #2 piston which is lean. So far, a carb rebuild/rejet. I cant tell from the pics but are all 3 cylinders sleeved?
    Oh gee, well thanks for the reply. Unfortunately, I don't know what/where the rod is. It has been running hot as this engine overheats everytime out on the boat. I just haven't been able to figure out why. I do not know much about the boat as I just bought it. I was told that engine was rebuilt, but I don't know how long ago and I don't know how many hours are on it. I bought 3 Mikuni carb rebuild kits and plan on taking care of that once I replace the piston/cylinder if the cylinder needs it. I didn't know the cylinders were sleeved. I can post more pictures if you need me to, to better assess the damage. I really want this boat to be in top shape, so what do you recommend I do to get it there. By the way the compression is as follows, cylinder 1: 60 (replacing the piston and maybe the cylinder), cylinder 2: 100 and cylinder 3: 100. The other engine is 120 across the board. By the way i have attached 2 more pictures of the head and an overall shot of the engine. Let me know what you think and thanks a lot for the help!

    By the way in the pictures the black lines on the piston and head is just a piece of the gasket that was stuck.

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  5. #5

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    You definitely need a new head. #1 is trashed. You should really figure out what did that to the piston/head...pretty sure some metal got in there somehow. With that much damage I'd tear the entire motor down and check the crankcase and make sure no junk got down in there.

  6. #6

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    Quote Originally Posted by 1 slow GTO View Post
    You definitely need a new head. #1 is trashed. You should really figure out what did that to the piston/head...pretty sure some metal got in there somehow. With that much damage I'd tear the entire motor down and check the crankcase and make sure no junk got down in there.
    It's funny you say that because when it first happened and the engine died, I tried to restart it. When it started again it sounded like a piece of metal was bouncing around in the engine and it sounded terrible, so I quickly shut that engine down and limped back to the ramp on the other engine. There are pieces of metal that look like metal "chips" (for the lack of a better term) next to the piston. You can see it in the pictures of the closeup of the piston. The picture is huge so if you blow it up you can see what I'm talking about. I definitely need to clean out the crank case, I'm just not exactly sure what I'm doing so its very frustrating. How can a piece of metal get in there and do that kind of damage?

    Since my engine has been overheating a lot since I got the boat, should I check the fuel filters? What should I check to prevent this from happening again once I get a new cylinder/piston?

  7. #7
    txgp1300r's Avatar
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  8. #8
    THE PLATE MAN JIM'S PERFORMANCE's Avatar
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    Quote Originally Posted by WATER WOODY View Post
    Whole motor has been hot/lean. Look at the rod color. Also, i only see 1 shim on the big end of the rod. How many hours on the motor? I can see part of #2 piston which is lean. So far, a carb rebuild/rejet. I cant tell from the pics but are all 3 cylinders sleeved?
    +1 Yes that rod thrust washer is gone so add a crank to the list.

  9. #9

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    Quote Originally Posted by JIM'S PERFORMANCE View Post
    +1 Yes that rod thrust washer is gone so add a crank to the list.
    Thanks for the insight. After ya'll pointed that out I see now where it is missing and thats why the piston moves around so freely. I PM'ed the guy selling the gp1300r, but will that fit in this boat?
    So far my WTB list looks like this, Is this all I will need (I have not taken the rest of the engine apart so I need to check and make sure the crank case is not cracked as well):
    head
    head gasket
    Piston
    Crankshaft
    the gaskets for each cylinder (can't remember the name of the gasket)
    Probably PV gaskets as well

    I have already purchased and received the PV clips and couplers and carb rebuild kits.

    One more question in a previous post Water Woody said "So far, carb rebuild/rejet." I am not sure what rejet means. Can someone please explain that for me?

  10. #10

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    Quick question. Now that I need to rebuild the engine, should I look at doing some performance mods to get some more power out of it? I'm thinking the cost would probably not be that bad compared to buying new parts anyway, but I really don't know what it would cost. Let me know what you guys think. I was reading on WCPorting.com and was thinking about getting that done. Is that a bad idea for this boat? I would love to be able to go faster (Right now I am at 57-60 on the speedo, obviously thats not accurate, so I would assume 50-52ish?).

    And yes I know what I do to one engine I need to do to the other. Is this a good idea or is it just to cost prohibitive?

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