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  1. #1

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    blown up gp1200r need advise

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ID:	260066ok good news everyone i blew up my gp1200 today so now what i need to know is wat Click image for larger version. 

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ID:	260065the f!#ck went wrong. Only finished rebuilding it 10 hours ago whilst doing that i removed the oil pump.So ive been running 40.1 premix and been havinClick image for larger version. 

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ID:	260064g a bit of trouble trying to get the fuel mixtures right so now ive come to the conclusion im going to remove my accelerator pump and change the jets Click image for larger version. 

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ID:	260063and popoff pressures. Ive removed all three heads and took photos to show you guys on what has gone wrong and you can help me identify the fault. But Click image for larger version. 

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ID:	260062in saying that i have been running premix now and thinking that it blew up because it was running too lean the fault seems to of occured on the exaustClick image for larger version. 

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ID:	260059 side of the piston so therefore i think water has entered into the cylinder orrrrr the cylinder has got too hot. But the prob is last time it blew upClick image for larger version. 

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ID:	260061 at 100 hours it was the same cylinder no1 so im wondering on who has good knowledge to help me out on maybe why this is occuring on the same cylinderClick image for larger version. 

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  2. #2

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    burn

    Quote Originally Posted by ryancoggo View Post
    Click image for larger version. 

Name:	IMG_0333das.jpg 
Views:	70 
Size:	270.0 KB 
ID:	260066ok good news everyone i blew up my gp1200 today so now what i need to know is wat Click image for larger version. 

Name:	IMG_0332sds.jpg 
Views:	57 
Size:	303.6 KB 
ID:	260065the f!#ck went wrong. Only finished rebuilding it 10 hours ago whilst doing that i removed the oil pump.So ive been running 40.1 premix and been havinClick image for larger version. 

Name:	IMG_0331.jpg 
Views:	184 
Size:	69.6 KB 
ID:	260064g a bit of trouble trying to get the fuel mixtures right so now ive come to the conclusion im going to remove my accelerator pump and change the jets Click image for larger version. 

Name:	gr.jpg 
Views:	70 
Size:	264.8 KB 
ID:	260063and popoff pressures. Ive removed all three heads and took photos to show you guys on what has gone wrong and you can help me identify the fault. But Click image for larger version. 

Name:	ggerve.jpg 
Views:	61 
Size:	50.7 KB 
ID:	260062in saying that i have been running premix now and thinking that it blew up because it was running too lean the fault seems to of occured on the exaustClick image for larger version. 

Name:	ggeerg.jpg 
Views:	59 
Size:	376.1 KB 
ID:	260059 side of the piston so therefore i think water has entered into the cylinder orrrrr the cylinder has got too hot. But the prob is last time it blew upClick image for larger version. 

Name:	efewfew.jpg 
Views:	62 
Size:	282.8 KB 
ID:	260061 at 100 hours it was the same cylinder no1 so im wondering on who has good knowledge to help me out on maybe why this is occuring on the same cylinderClick image for larger version. 

Name:	dsgaegwea.jpg 
Views:	57 
Size:	63.1 KB 
ID:	260060

    1. pull the jug and make sure the crank pin did not lose any bearing material.

    2. if the crank is solid, check your pulse line for cracks or any damage.

    3. if that ok, what do the plugs look like on the 2 other cylinders?

    4. if they are not lean, then pull the carb apart for that burned cylinder and look for issues.

    5. no issues, pull all the carbs apart, clean them and do the dual fuel supply and rejet to oside bills specs in the FAQ's section. lose the accelerator pump too.

    i did it and it worked great. was a bit rich, but i got it worked out. i chose no chokes, but i would not do that again.

    if you remove your gas cap, and blow air in reverse from the supply line at the carbs, to the tank, it can help find probs. keep air pressure low.

    bump your oil ratio to 32:1 for first couple tanks. then 40:1 is ok

    you want to start at your tank and go thru all the lines, filters, etc...

    i think thats all, IMO

    when you do a rebuild, check it all. reeds, carbs, squish,ring gaps,fuel supply,etc...

    hope it works out for you.
    Last edited by rockerc; 12-11-2011 at 05:30 AM. Reason: spelling

  3. #3
    Myself's Avatar
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    That almost looks to me like a PV dropped and cut into the piston. Did you take them apart, clean, inspect, and upgrade the clips while you were rebuilding?

    Also that PV kissing the piston could have been the knock you were hearing.

  4. #4

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    found out what the problem was ive never seen it before but the guide pin on the piston that holds the piston ring in position was pushed in for some reason therefore letting the piston ring spin and got caught on the exaust port pretty lucky it on fuked the piston and not the barrel,crank etc lol

  5. #5
    A child of five would understand this. Go get one. pierowman's Avatar
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    As i understand it that is a very common issue with the yamaha pistons.

  6. #6
    Moderator beerdart's Avatar
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    Yes it is..
    Quote Originally Posted by pierowman View Post
    As i understand it that is a very common issue with the yamaha pistons.

  7. #7
    yup!

  8. #8
    Myself's Avatar
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    Oh nice, way to go Yamaha.
    Highly educated kid behind a computer screen at Yamaha R&D: "This is a great design and we should build it like this."
    Real World Mechanic in anywheresville, USA: "What a bunch of [email protected]$$es, have they ever worked on anything they designed?"

  9. #9

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    lol yea i was pretty devo considering i only put 2 hours on it now i need a new piston but thank fuk it didnt wreck the bore otherwise i would be very pissed off lol

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