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hi all, i need some help, i rode my 2001 gp1200r over the weekend and it suddenly cut out on me, it started again but would not rev over 4000rpm, and sounded like it had a misfire. i took it to the yamaha dealer who did a compression test and said the 1st cylinder was only showing 40psi, the other 2 were at 110psi. he recommended a complete engine rebuild, both top end and bottom end, ie new pistons and a new cranckshaft. does this sound like the correct advice and would i need to do both? the mechanic said i could just to the pistons but more than likely in a month or two the crankshaft would break as well, if i dont replace the crankshaft at the same time? any advice would be greatly apreciated, thanks
 

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hi there to be honest with you i have had the same problem and i did the work myself it was fairly straight forward.. i just put in 3 new pistons and rings and new small end bearings and a new head and cylinder gaskets set me back about £350 for all parts from riva racing in america thats for standard parts.. :eek:
 

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hi, thanks for the reply, one question, did you have to go for oversized pistons? i was told that i had to go for one size bigger than standard when putting in new pistons?
 

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no you dont have to replace the crank too,, but if the cylinder walls were scarred bad there might be metal shavings in the case, and that will destroy a crank....if anything take the motor apart, clean the cases out and use thesame crank....ive ran oem cranks with 250+hrs on them and they work fine..

you should do the work yourself, its really easy and you'll save a HUGE amount of money..

also no you dont have to go wit a biger piston,,, whoever told you that is wrong... the cylinder has a number on top of it.. they relate to the piston that should be in it....

0-5 =A piston
6-10 =b piston
11-15 =c piston
16-20 =d piston

the only way you would oversize a piston is if you got the jug honed or bored... and dont let the average shop do that to these cylinders, these are nickasil plated and can only be honed correctly with a diamond blade.... if your jug is ruined then just order a new one off of ebay, buy the corresponding piston, and your good to go....

are you running pre-mix? if not you should consider switching or making sure the oil lines are tight on the carbs,,,,, these lines are prone to popping off, then the motor seizes...
 

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What is the best way to clean/flush aluminum particles from the crankcase without removing the engine and splitting the cases. I'm in the process of replacing #1 piston and rings now, so the #1 jug is off. I noticed a little bit of aluminum dust inside the case and was wondering if I could flush it with something and then pump it out.
 

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What is the best way to clean/flush aluminum particles from the crankcase without removing the engine and splitting the cases. I'm in the process of replacing #1 piston and rings now, so the #1 jug is off. I noticed a little bit of aluminum dust inside the case and was wondering if I could flush it with something and then pump it out.
I know this is an old thread, but could anyone answer this question?? I am in the same process and unsure if I would be capable of reassembling the crankcase after cleaning it out by hand.
 

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I just got a gallon of diesel and poured it in the crankcase and syphoned it out with a hand syphon pump. I repeated this process several times until I couldnt see anymore aluminum pieces.
 

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I just got a gallon of diesel and poured it in the crankcase and syphoned it out with a hand syphon pump. I repeated this process several times until I couldnt see anymore aluminum pieces.
And it worked? the crank didn't go later on? I'm just afraid i'm gonna have to pull the engine apart again because i didn't do something right. I'm paranoid lol.
 

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Really depends on how much material got into the bearings and how long the cylinder may have been ran without oil if the oil line fell off. Really no rhyme or reason as too many variables come in to play. Be save than sorry, but when budget comes into play, that is another story.

I once used brake parts cleaner and shot it in the oil feeds to the bearings. You will need some pressure to seperate the trash. Got out the really small fragments and used some shop wipes together with rotating the crank to wipe it all out. Could also remove engine.

The roller bearing on the rod/crank is crucial. If any notchy feeling in there, time to swap. Can go and take the cases with it.
 

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Really depends on how much material got into the bearings and how long the cylinder may have been ran without oil if the oil line fell off. Really no rhyme or reason as too many variables come in to play. Be save than sorry, but when budget comes into play, that is another story.

I once used brake parts cleaner and shot it in the oil feeds to the bearings. You will need some pressure to seperate the trash. Got out the really small fragments and used some shop wipes together with rotating the crank to wipe it all out. Could also remove engine.

The roller bearing on the rod/crank is crucial. If any notchy feeling in there, time to swap. Can go and take the cases with it.
I don't think hardly any material actually got into the bearings.. My piston toast, yes, but it's not nearly as bad as pictures of some others ive seen on here where the oil line fell off. The crank looks mostly clean of debris but there are a few miniscule metal flakes around the rim of the crankcase under the piston. I think I'm just going to flush it out with some yamalube and gasoline mix repeatedly.
 
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