YFZ450 crank and piston Problem

i just wanted to ask if it is possible to use a flex and shave a bit off the piston at the bottom where the pin goes through connecting the piston to the rod since it touches it by about 2mm. please let me know what you think. thanks

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Autos & Vehicles

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• big bore
• how to
• yfz450
• raptor
• banshee
• 350
• 700
• 480
• stunts
• extreme
• installing
• fps

[ludwig7710]

if you figured out anything let me know please i have the same piston on order for mine, thanks

[uae3276]

@ludwig7710 i didnt figure anything out, all i did was: taking a sand stone which is like sand paper except hard and put it on a drill, the one with the cord since it needs power, then i just started shaving of at the crank where it was touching, i also did a bit at the bottom of the piston but i think that was a bad idea since the piston might break now, so i would advise only to do it on the crank if you have the same problem. ans seems to spin fine now....no need to split engine.

[ludwig7710]

@uae3276 your not worried that you threw the crank out of balance by grinding some off?and i already split cases on mine i decided to do every bearing and seal in it since i had it apartso i might be able so see something a little different when i put it together. im just worried you threw the crank out of balance grinding on it and its really gonna tear things apart. i wouldnt be worried about the piston as much since most of the force applied to it is on top never the bottom.

[uae3276]

@ludwig7710 ok, now you got me worried, will it throw it of balance even if its just a thin layer off the top like less than a milimeter? and i did it to both sides, so what i would suggest you do is to wait till your piston arrives, put it on the crank and check, how will i notice that its of balance?

[DJohnson8132004]

Mine just did the same thing but my piston got stuck on the crank. We had to pull the whole thing apart and got a new crank, rod, and piston. The bearing went bad on mine, it actually was in about 50 different chunks. Hopefully this is a little help for you.

[Tooextrememx]

where you put in an oversize piston you sometimes need to machine the cases where the cylinder meets the lower end.what is happening is when the piston reaches the bottom it is getting caught on part of the lower case this problem happens alot when you bore and engine out more then 2mm.

[scrimmy6969]

the piston should not contact the crank. and you should not have taking material out of the crank or piston. something is not right. what crank and rod are you using?

[ludwig7710]

@uae3276 im sorry i didnt get to you sooner you may be buying a crank in the near future which isnt cheap but look at it this way if the crank goes bad you can buy a stroker kit for it to lol did you get new cams along with the big bore?

[ludwig7710]

@uae3276 you will know as soon as you start it it will vibrate really bad especially when you get it up to speed. i guess the worst thing it will do is ruin your bearings and break your crank hopefully it doesnt punch a hole in the case. usually cranks are balanced to almost perfect specs and grinding it down may have thrown it way out which will give you a pretty nasty vibration. my guess is that it will because the counter weight shaft is balanced with the the crank to ensure no vibrations