Engine rebuild question

[yamaha69x]

Hey, i think my yfz has about 75 hours on it now, what should i do? i read that i should do a rebuild, DO I HAVE TO? and what's a rebuild exactly
can i just simply change the piston to a new one and gaskets to make it running like new?

Thanks in advance.

[joshduke]

Depends a lot on how it was ridden for those 75 hours. What type of riding do you do? How does it run?

[yamaha69x]

it actually runs great, i don't feel aynthing is wrong with it, and i never push my bike, and take care alot when im riding.

[Haas33]

I think you would probably be ok then to just rebuild your top end

[climb-101]

what year bike is it

[yamaha69x]

haas33, can you please explain further more, what is rebuilding top end? what do i need what will it do.

and it's a 2009, bought it in 2010

[Haas33]

it is just a new piston, rings, wrist pin, and top end gasket kit. you can buy piston kits that have all of those things. you might also want check your valves or have a mechanic do it and they will probably need re shimmed.

[silveryfz]

dont wanna steal the thread, but im picking up an 06 with blown head gasket for my wife. gonna go thru and rebuild top end. anything else i should look for when tearing it apart?

[cbohenek]

Dont rebuild unless you need too. Why waste $ if you dont need too.

[manny530]

Originally Posted by cbohenek

Dont rebuild unless you need too. Why waste $ if you dont need too.

maybe he wants to be cautious and it deff would be cheaper to rebuild a running motor than a blown up motor

[yamaha69x]

Thanks everyone :), i think i'll wait until the summer is over then do it, i think that's a good decision?

[Haas33]

if it is still running fine you should be ok. but just remember if the motor blows it will make it way more expensive to get running again. But I think it would be a good decision to wait so you don't miss out on any riding in the summer

[atc31510]

silveryfz I would have the oil mod done to it also or you could have major problems in the future with your rod bearing. That is if it has not already been done. I just had it done to one of my bikes cost me $180 but is well worth it.

[climb-101]

Originally Posted by cbohenek

Dont rebuild unless you need too. Why waste $ if you dont need too.

if you make it to the point of "needing a rebuild" its going to be expensive. you should be fine just changing the cylinder and piston. I would get a new piston (same size you have) and send the new piston and old cylinder to millenium tech, and have them re nick the cylinder. Doing it this way cost the same sa replacing the cylinder except you get a much better fit for the piston since the size the cylinder to match the piston.

[kb motorsports]

Originally Posted by yamaha69x

Hey, i think my yfz has about 75 hours on it now, what should i do? i read that i should do a rebuild, DO I HAVE TO? and what's a rebuild exactly
can i just simply change the piston to a new one and gaskets to make it running like new?

Thanks in advance.

I wouldn't rebuild the motor unless it was showing signs of wear or you want more power. 75HRS of recreational use or flat out racing with consistent servicing doesn't require a rebuild from my experience. I never did the oil mod on my 2004 YFZ and never bit the bullet refusing to do so. My 04' YFZ was rode every day around the farm and raced on the weekends for three years straight without one single failure. The point i'm trying to make here is by servicing the YFZ often you'll accumulate hundreds of trouble free hours.

[yamaha69x]

Originally Posted by kb motorsports

I wouldn't rebuild the motor unless it was showing signs of wear or you want more power. 75HRS of recreational use or flat out racing with consistent servicing doesn't require a rebuild from my experience. I never did the oil mod on my 2004 YFZ and never bit the bullet refusing to do so. My 04' YFZ was rode every day around the farm and raced on the weekends for three years straight without one single failure. The point i'm trying to make here is by servicing the YFZ often you'll accumulate hundreds of trouble free hours.

Yeah i agree, i always service early

[mixxer]

lots have already answered the "why rebuild" question correct .... and it's no joke....rebuild is the way you keep your fav engine from becoming your fav boat anchor....

lots of hours will turn your engine into an electic start time bomb....

short skirt / slipper pistons are awesome for low friction and high rpm performance, but then they wear , things dont just degrade.... they can grenade....

so... hone the cyl and a fresh piston & ring setup.... shim the valves while you have it down.... good to go

[mixxer]

Originally Posted by climb-101

if you make it to the point of "needing a rebuild" its going to be expensive. you should be fine just changing the cylinder and piston. I would get a new piston (same size you have) and send the new piston and old cylinder to millenium tech, and have them re nick the cylinder. Doing it this way cost the same sa replacing the cylinder except you get a much better fit for the piston since the size the cylinder to match the piston.

hadnt thought of that for a stock bore.... good call though...

on my own machines i always have the bigger bore work done for .0006" clearance... better ring seal and better heat transfer....

[yamaha69x]

So i was looking up rebuild kits on ebay, i came across top end rebuild kits, bottoms end, full rebuild kits, big bore kits, stroker kits.... I'M CONFUSED!! which should i get

[yamaha69x]

Bump