10 yz450.when to rebuild?


21 replies to this topic
  • thestuz

Posted October 13, 2011 - 01:57 AM

#1

my mates 2010 450 has just hit 100 hours.
hes a pretty average rider and changes oil often and does not race hard.
how many hours can he go before needing to change out his piston. would 150 be safe?

  • tech24

Posted October 13, 2011 - 04:31 AM

#2

Impossible to say but my maint plans are the following

timing chain about ever 50hrs
piston about ever 100hr

and thats it unless I find something else in need. Could probably go twice that but I'm babying this one.

  • CRF100biker

Posted October 13, 2011 - 05:53 AM

#3

i say until it blows up or evidences a problem. my '98 yz400f hasn't even needed the valves adjusted in 13 years. hoping for 14 when i check them at the end of this season. all the bike has needed is fluids, tires, filter cleanings, brake pads, sprockets/chains, levers and grips.

  • OUTERLIMITS

Posted October 13, 2011 - 09:38 AM

#4

i say until it blows up or evidences a problem. my '98 yz400f hasn't even needed the valves adjusted in 13 years. hoping for 14 when i check them at the end of this season. all the bike has needed is fluids, tires, filter cleanings, brake pads, sprockets/chains, levers and grips.


Nice, gotta love it! :thumbsup:

  • DBMX 925

Posted October 13, 2011 - 02:23 PM

#5

i say until it blows up or evidences a problem. my '98 yz400f hasn't even needed the valves adjusted in 13 years. hoping for 14 when i check them at the end of this season. all the bike has needed is fluids, tires, filter cleanings, brake pads, sprockets/chains, levers and grips.


Way better to wait for the 2k grenade that throw a couple hundred at her for piston rings and timing chain. Great advise.........

  • CRF100biker

Posted October 13, 2011 - 04:22 PM

#6

why would you need to do all that to a stock bike that is properly maintained and set up? i'd actually look into these things if they were prone to wearing out or coming out of adjustment, but my bike hasn't missed a beat in 13 years. i keep my air filter really clean, change the oil and filter at the same time quite often, keep track of the plugs, make sure i always have a good level of coolant, watch the valve adjustment, just generally watching everything the manual tells me to watch. it sure makes owning a 4-stroke a hell of a lot cheaper when you're not buying parts just because of paranoia. then again, maybe my old tractor is just simply a lot more reliable than the new stream-lined looking bikes.

big bore yamahas are a lot more reliable than everyone makes them out to be. if you follow what the service manual tells you to do and don't cut corners then doing rebuilds shouldn't be necessary on a stock motor.

  • rickallen124

Posted October 13, 2011 - 06:06 PM

#7

At 100hrs I'd put a new piston and rings in along with a new timing chain just to be on the safe side.

  • thestuz

Posted October 14, 2011 - 01:13 AM

#8

cool. yeah it sounds like the cam chain is a little bit on the rattly side so hes prob gonna do it soonish.
but i dont think ive heard of a 10 model 450 blowing up yet. just gearbox problems i think.

  • eazrider

Posted October 17, 2011 - 08:16 AM

#9

At 100hrs I'd put a new piston and rings in along with a new timing chain just to be on the safe side.

I pulled my '10 down to put in WR ratios, and the end gap on the rings showed .001 wear from nominal stock. New spec was .008-.012, mine was a "snug" .013....Cam chain was tight.... piston looked good, but wasn't mic'd with that little wear on the rings.... No adjustment required to the valves. If it make one feel good, all of these things could be changed. :thumbsup:

  • crf450319

Posted October 17, 2011 - 09:04 AM

#10

An ounce of prevention is worth a pound of cure.

Suggesting that someone wait until there's a catastrophic failure before replacing the top end is one of the most rediculous statements I've read here on TT. That's so far off base, I'm just going to leave it alone.

Just like rickallen124 I normally run my pistons for 100 hrs and replace the timing chain every 50. I am mechanically inclined and do all of my own work, I can have the t. chain replaced in 30/35 min at a cost of $23. I just replaced the top end in my '09 yz450f after 110 hrs, I took the cylinder off and noticed that I was starting to wear through the nikasil and I had some ring float going on. I replaced the cylinder with an OEM unit ($256 shipped) and rode the bike for the first time last night.

I have literally 5 pages worth of maintenance items I've done, I record everything - oil changes, susp. fluid changes, air filter maint., grease jobs etc etc. I run Amsoil MCF and change it every 6.5 - 7 hrs of runtime and I ride MX only in "B" and Vet master. I've owned 14 or 15 motorcycles, road-raced blah blah blah. I like to think that I know what I'm doing (for the most part). For the type of riding I do, from now on I think I'll replace the piston rings every 50 hours as well and try to eliminate the ring float/fatigue.

I would think though, that replacing the top end every 100 hours would be a good plan. Neither excessive, or too slack.

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  • FZ1426

Posted October 20, 2011 - 07:56 AM

#11

The manual says replace the piston, pin, and rings at 12.5 hours or "as required".

You can read as much or as little into that as you want. It depends on a lot of things, but 100 hours is a stretch to say the least.

  • grayracer513

Posted October 20, 2011 - 08:16 AM

#12

The manual says replace the piston, pin, and rings at 12.5 hours or "as required".

You can read as much or as little into that as you want. It depends on a lot of things, but 100 hours is a stretch to say the least.

As you say, that depends...

100 hours of B level MX racing is a lot. 100 hours of recreational riding is nothing. The bike I'm on now has roughly 100 on it, and it's in good shape. The '03 I had had well over 300 when I sold it. Never opened up.

  • ducanh2410

Posted October 20, 2011 - 01:02 PM

#13

It depends on how you ridding, if you love to go over rev, it'd be about 20-30 hours to change the piston kit. But if u go for low rev, it will be more than 50 hours. I often do that on my 10YZ450F.

  • crf450319

Posted October 20, 2011 - 01:33 PM

#14

20 or 30 hours ?

I've got a buddy that runs A/ Vet A on a yz250f and this guy LIVES on the limiter, we all bug him that the bike makes more power when it isn't going "ba ba ba ba ba ba ba ba" as a joke. He's a journeyman mech. by trade and replaces his top end every 80 hours.

I've always gone 100 hours on a top end on my 450's.

It's all good though, I don't think there's a right or wrong way. However you want to do it.

Edited by crf450319, October 20, 2011 - 03:37 PM.


  • ducanh2410

Posted October 21, 2011 - 08:55 AM

#15

20 or 30 hours ?

I've got a buddy that runs A/ Vet A on a yz250f and this guy LIVES on the limiter, we all bug him that the bike makes more power when it isn't going "ba ba ba ba ba ba ba ba" as a joke. He's a journeyman mech. by trade and replaces his top end every 80 hours.

I've always gone 100 hours on a top end on my 450's.

It's all good though, I don't think there's a right or wrong way. However you want to do it.


Yup, I ask my friend in US and he said so, 100 hours is OK but you know in Vietnam there isn't any dealer that sell dirtbike so I don't want to mess up with my bike. Just want it to be safe then.

  • crf450319

Posted October 21, 2011 - 10:31 AM

#16

Yup, I ask my friend in US and he said so, 100 hours is OK but you know in Vietnam there isn't any dealer that sell dirtbike so I don't want to mess up with my bike. Just want it to be safe then.


Ahh, I see. What are you doing out in Vietnam ?

  • ducanh2410

Posted October 23, 2011 - 02:35 PM

#17

Most of them are riding in trails, but I just love racing and freestyle

  • atomic410

Posted October 24, 2011 - 06:34 AM

#18

so on a supermoto bike piston every hour or so and crank/lower end rebuild when?

  • grayracer513

Posted October 24, 2011 - 08:48 AM

#19

piston every hour or so ...?

Is this a typo?

  • atomic410

Posted October 24, 2011 - 09:18 AM

#20

yeah sorry 100 hours. my #board must have been off. i fail





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