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2010 engine rebuild. Thoughts?

By Zien19,
in YZ400F/426F/450F/450FX

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Zien19

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Hello all I have a 2010 450 that burns oil. Only has 32 hours It (not a very happy camper) must be rings or valve seals. Puffs when under cracking of the throttle. Now to my question. I'm going to put a new piston in and was looking at the 13 to 1 cosworth set up. Any thoughts on the reliability of cosworth. I don't want to go any higher on the compression so I don't have to run straight race fuel. Or just oem or wiesco? Cams? I don't really need any more power as I ride mostly mx. Looking for the hot setup. Any insight would be appreciated.

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grayracer513

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OEM is the most reliable, and they are forged pistons, too. 

 

Generally, rings cause smoke under a load, whereas valve seals will oil up the upper cylinder while off the throttle, then it puffs when you open it back up.  Valve seals are cheap and easy (if you have access to a spring compressor).

 

I recall an '09 that developed a serious piston slap at fairly low hours.  Can't remember what exactly the problem turned out to be, but it seems like it was part of the Nikasil plating flaked off to get it going.  Definitely not something that happens often at all.

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rdefonce

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OEM is the most reliable, and they are forged pistons, too. 

 

Generally, rings cause smoke under a load, whereas valve seals will oil up the upper cylinder while off the throttle, then it puffs when you open it back up.  Valve seals are cheap and easy (if you have access to a spring compressor).

 

I recall an '09 that developed a serious piston slap at fairly low hours.  Can't remember what exactly the problem turned out to be, but it seems like it was part of the Nikasil plating flaked off to get it going.  Definitely not something that happens often at all.

Wow that's a good thing that doesn't happen often.:-o

I'd also be ticked off if after only 32 hours my 450 started that s#!t!

 

Zien19 maybe you should check your stock piston before dropping the cash for a new one . . . it might be just fine, especially since they are durable forged units (I didn't know that!)

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Zien19

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Ya im thinking stock setup is the key. I had over 100 hrs on my 06 450f and it didn't burn a drop of oil. My 2010 doesnt burn much oil either probably about 50 to 100ml per ride. I give it a little drink every secound ride. It made it through the season and winter is upon us.(located in northern BC Can). So i figured i would give her a little love in the off season. Im pretty convinced its valve seals as the valve clearance has checked out right on par and there is no lack of preformance what so ever. Still love this bike. I guess sometimes you win and sometimes you don't. Maybe ill just do rings, valve seals, timing chain and call it good depending on how it looks when i open her up.

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DC_Excitement

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I just replaced a piston in mine at roughly 300 hours ('06 with the original OEM parts throughout; first time opened up).  I had the cases split to swap two gears in the trans to different ratios.  The interior of the engine was in phenomenal condition overall.

wow,

it totally pays off to run quality oil and change it often. im hoping my 2010 can stay that clean internally.

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zeuszuki

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Hello all I have a 2010 450 that burns oil. Only has 32 hours It (not a very happy camper) must be rings or valve seals. Puffs when under cracking of the throttle. Now to my question. I'm going to put a new piston in and was looking at the 13 to 1 cosworth set up. Any thoughts on the reliability of cosworth. I don't want to go any higher on the compression so I don't have to run straight race fuel. Or just oem or wiesco? Cams? I don't really need any more power as I ride mostly mx. Looking for the hot setup. Any insight would be appreciated.

My guess is with Gray' - valve seals.

At 32 hours it is just run in, my '11 had the top end pulled down at 76hrs - piston measured up fine , new rings ( you get spares in your spares kit so may as well use them up ), good to go.

My riding buddies '10 has 200 hours on it, doesn't burn a drop. No need to stress :-)

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Zien19

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No spares kits in the US market. Bummer.

 

Grey  I believe it ended up being valve seal. See pic of the on darker intake valve. My question is since I had it tore down anyway I was going to do rings as well. I pulled the cylinder and everything measures out fine and the coating on the cyl is all intact. But where the skirt rides you can feel the a ripple at the top and bottom of the stroke. It isn't scored and you cannot feel anything with a finger nail. The piston also measures within spec. Is this something to be worried about?  Would you hone before rebuild?  Also check out photo 1328 there are oil recesses drilled in every valve except the one exhaust. Forgot by factory?

 

Thanks in Advance.

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Grand Master

grayracer513

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The ripple you're feeling at the top and bottom is a ring "shadow".  (See the arrows in the picture) These appear as a result of the rings "twisting" in their grooves at the top and bottom of the stroke as they reverse.  In the case of the oil rings, it also usually means that the expander ring has worn into the scraper rails a little so that the whole set is loose in the groove.  If the new rings are looser in any of the 3 grooves when they are half way inserted than they are when you push them all the way in, the ring grooves are worn and the piston should be replaced. 

 

I always hone a used cylinder using a silicon carbide or aluminum oxide ball hone, like those from Brush Research.  (Read: https://www.thumpertalk.com/topic/399309-new-piston-06yz450f-advice-needed/#entry3565759 )

If the shadows don't disappear in under 15 seconds of actual hone time, then you need to have a machinist check the depth of them.  If they are more than a half thousandth deep, the new oil rings will dig at them as they cross them and wear more rapidly.  More than a thousandth, and the bore is worn beyond serviceability.

 

The valves look a little sketchy, too.  Check the darker one especially.  The edge of the wear mark on the face cannot have even a slight defined ridge to it.  In the picture, the valve in the foreground is OK, the one in back, not.

 

Untitled-4_zpsb586445e.jpg  bore.png

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Zien19

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The ripple you're feeling at the top and bottom is a ring "shadow".  (See the arrows in the picture) These appear as a result of the rings "twisting" in their grooves at the top and bottom of the stroke as they reverse.  In the case of the oil rings, it also usually means that the expander ring has worn into the scraper rails a little so that the whole set is loose in the groove.  If the new rings are looser in any of the 3 grooves when they are half way inserted than they are when you push them all the way in, the ring grooves are worn and the piston should be replaced. 

 

I always hone a used cylinder using a silicon carbide or aluminum oxide ball hone, like those from Brush Research.  (Read: https://www.thumpertalk.com/topic/399309-new-piston-06yz450f-advice-needed/#entry3565759 )

If the shadows don't disappear in under 15 seconds of actual hone time, then you need to have a machinist check the depth of them.  If they are more than a half thousandth deep, the new oil rings will dig at them as they cross them and wear more rapidly.  More than a thousandth, and the bore is worn beyond serviceability.

 

The valves look a little sketchy, too.  Check the darker one especially.  The edge of the wear mark on the face cannot have even a slight defined ridge to it.  In the picture, the valve in the foreground is OK, the one in back, not.

 

Untitled-4_zpsb586445e.jpg  ?bore.png

 

The Ripple runs up and down opposite to the ring shadow and is just as wide as the skirt from the piston. ie vertical plane not horizontal. The shadow you pointed out can be seen but not felt. It was hard to get a good pic with the flash and light situation. I will find a hone and see if it smooths out and will look at the valves. Any other info will be greatly appriciated.

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