100 hrs on 2014 yz450f, shim valves or replace them?

[jz125]

^{Kinda shaking my head here. Do you own a Yamaha YZ450F?}

 

^{Just ride it}

[ttr230rider6]

What is the point in replacing something that isn't worn out?

The rings can start to loose their seal before any significant wear to the piston occurs. In this case, neither of these components is necessarily signaling that it needs immediate attention by showing symptoms of wear, so the tear down will amount to preventative maintenance. In such cases, you inspect what you find and decide whether it needs attention or not. In general, unless the rings are nearly new, you should replace them if you pull the cylinder off. Whether to replace the piston becomes something like predicting the future. You can observe and measure the wear you find, then take an educated guess as to how long it will last before it really needs attention, then balance that against whether you want to put it together now, then take apart later to replace the stuff you don't do now, and against the fact that if it isn't completely used up, you're throwing money away in the form of use you didn't get from it. All this considering that it's much more expensive to wait until something breaks to fix it, and that risk increases the longer you leave things together.

Thanks for the info man, really appreciate it. 2 more questions before I start.

1. Should I drain the oil before I start?

2. how can you tell by looking at the rings of they are worn out or need replacing?

[grayracer513]

1) Doesn't matter, but it's a good idea to change the oil after the engine's been opened up.

 

2) Measure the end gap per the manual instructions.  As the ring wears, the gap widens.  If you remove the cylinder, just plan to replace them.  They're only $20 a set or so. 

[adam8781]

replace the damn rings,  They are cheap, If I owned the bike it would be getting a 13.5:1 piston lol.

[ttr230rider6]

^{Kinda shaking my head here. Do you own a Yamaha YZ450F?}

^{Just ride it}

Doesn't matter what it is, it still has to be maintained

[GHILL28]

replace the damn rings, They are cheap, If I owned the bike it would be getting a 13.5:1 piston lol.

Why?

[adam8781]

Blow by ruins oil, accelerates wear etc. Its a very cheap easy thing to replace. These bikes are 1/8 an indy car motor. If the motor is open, hes 4 bolts away.

Not the end of the world if you dont but a 14 yzf is a pretty penny, I dont mind spending a nickel here and there to keep it in top shape.

[GHILL28]

No I meant the high comp piston.

[ttr230rider6]

Got the valve cover off and I am only seeing 4 valves?! I thought the yamahas had 5? Or did they change it in 2014??

EDIT: I know now it is 4 lol

Edited May 4, 2016 by ttr230rider6

[ttr230rider6]

I will get the correct measurements in the morning. I was going by the wrong specs in the book. I didn't read the full thing and I went on an assumption I was doing it right. I will be much more careful and will read more in depth from now on

Edited May 4, 2016 by ttr230rider6

[GHILL28]

Where the hell are you getting those numbers?

[ttr230rider6]

Where the hell are you getting those numbers?

Oh my god, I was going by valve guide specs in the manual, i am an idiot. I just went through the manual and I found the correct numbers. I assumed I was reading the right section and assuming always screws me over. I will get the correct measurements in the morning.

Edited May 4, 2016 by ttr230rider6

[GHILL28]

.005-.008" on intake

.008-.010" on exhaust

[toten]

At least you figured it out before screwing anything up. 

[ttr230rider6]

Just checked them again, here is what I recorded

The exhaust valves are still within spec (0.2mm-0.25mm) and the intake valves are slightly out of spec (0.13mm-0.2mm)

Going to remove my intake cam after work to see what size shim is in there now so I can figure out which size I need.

[ttr230rider6]

At least you figured it out before screwing anything up.

Got that right! I'm pretty sure I got it under control now [emoji106]

[GHILL28]

You are positive it's below .013mm (.005")?  Mine measures EXACTLY at that limit and hasn't budged.  I would double check before you mess with it.

[ttr230rider6]

You are positive it's below .013mm (.005")? Mine measures EXACTLY at that limit and hasn't budged. I would double check before you mess with it.

The 0.005" feeler slid in with a little bit of stickyness to it. But the number in mm on the feeler said 0.127 mm, but when I convert 0.13 mm online it comes out to 0.005118, which is bigger than 0.005 so really I am still in spec? But shimming it 0.05 mm would obviously help it by putting it up around 0.18 mm

[grayracer513]

.005-.008" on intake

.008-.010" on exhaust

Those are the specs for the old 5 valve engine.  for the '14, they are:

 

Intake:  0.13–0.20 mm (0.0051–0.0079 in)

Exhaust:  0.20–0.25 mm (0.0079–0.0098 in)

[GHILL28]

 

Those are the specs for the old 5 valve engine.  for the '14, they are:

 

Intake:  0.13–0.20 mm (0.0051–0.0079 in)

Exhaust:  0.20–0.25 mm (0.0079–0.0098 in)

 

 

 

That's what I just said, with .0001"-.0002" of rounding, since tenth's aren't measurable with feeler gauges anyway....

The 0.005" feeler slid in with a little bit of stickyness to it. But the number in mm on the feeler said 0.127 mm, but when I convert 0.13 mm online it comes out to 0.005118, which is bigger than 0.005 so really I am still in spec? But shimming it 0.05 mm would obviously help it by putting it up around 0.18 mm

 

I would leave it.  Maybe check them every 20h and adjust once it's actually OUT of the range.