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Aka.Goose

My yz is getting louder and smokier...

26 posts in this topic

Hey guys, just got Gorman out of my system the last few weeks since it's closed now for red stickers...I did two full days rides one week (camped with my girlfriend in 25 degree weather, woke to some snow on the ground, what a trouper)...I was using Motorex 10-40, put around 5 hrs on it, came home for a few days, cleaned the bike, did general maint., air filter etc. and changed the oil (which was quite dark and not much drained, a lot must've burned off?) to Amsoil 20-50 as the next few days rides were going to be in much warmer weather...Went back and did two more full days rides, but noticed the bike has been getting much louder...All of the usual loud yamaha noises that took me so long to get comfortable to hearing (after hearing many other yamis sounding the same way) are getting much louder, and I'm now emitting lots of bluish white smoke, so much so that I had to ride in the back of the pack due to a few tight cliff ledge trails...I'm sorry I can't be more specific about the type of noise, but that's the thing, it seems louder everywhere, front left cylinder, lower right cylinder, and from the clutch (although I think that's because the hinson clutch and cover are actually louder than stock?)

On the other hand the bike is running killer...Passed it to the most knowledgeable rider amongst us and he said it felt great, just sound like it's about to blow! I did have a bit harder time starting it in the morning than usual, but I chalked that up to it still being a bit cold (55-60 degrees or so)and having 20-50 weight oil in...After it was running for a while it was completely necessary to use the hot start (usually if I stall out I can just start right up without choke or hot start)...

What do you think guys, do I need to pull it apart, check the valves, cylinder wall, piston/ring, timing, where should I start? The only issue I've had previously was a faulty cam chain tensioner which allowed the cam chain to skip a tooth, both the tensioner and chain were replaced...

The fairly thick bluish white smoke scares me...

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Sounds like your burning oil, have you checked your valve clearances? Possible your valves guide seals are letting oil leak through. When was the last time you replaced the piston and rings?

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When was the last time you replaced the piston and rings?

Not yet, the bike only has about 20 hours on it...

The valve clearances/seals were fine about 10 hours ago, but yeah, def burning some oil, so I guess that's where I'll start...

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Other things that would cause you to burn oil are worn out valve guides and blocked crankcase vents, over-filling crankcase oil, or air leaks in crankcase.

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Other things that would cause you to burn oil are ... blocked crankcase vents, ... or air leaks in crankcase.
Since the breather IS an air leak in the crankcase, I wonder if you'd care to elaborate on that?

Blocked breathers will cause the engine to push oil seals out, but not burn oil.

Likewise, overfilling is not likely the culprit, since once the oil has burned down to normal levels, it will no longer be overfilled, and it will quit doing it.

My take on this, given the worsening noise issue, is a bad piston, and damage to the rings and/or cylinder wall.

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Awe Grey, I was looking forward to your input, yet once hearing it I cringed...

Here's what I'm thinking, maybe when the cam chain tensioner failed and caused the chain to skip (twice, once originally, and once at the shop after resetting it)...the valves may have gotten bent ever so slightly, which you wouldn't notice on a clearance and seal check...Once they're off just a hair, don't they gradually get more and more bent, stop seating correctly, allowing oil through, and the extra noise everywhere is the oil burning off and going low...

I don't know I'm just making it up as I go I guess...I'll be opening it up soon...maybe bring it to the shop...

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...Once they're off just a hair, don't they gradually get more and more bent, stop seating correctly, allowing oil through, and the extra noise everywhere is the oil burning off and going low...
Uh, ....no. Impacting the piston bends the valve at the face. There is nothing that would influence them to bend further over time, and the valve faces don't seal against oil in any case.

Very creative, though.

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greyracer513, not much to elaborate on. I sorely misinterpreted something I read elsewhere. Sorry to cause any confusion.

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Ok, well, didn't have time to open everything up yet (didn't even check the plug yet), but I did wash it down, drained and flushed the gas tank (the gas that drained was peculiarly dark, darker than premixed gas?), cleaned the air filter (didn't really need it), swapped the oil filter since I just wasted money on a zip ty magnetic oil filter cover and it came with a new metal one, and sure enough when I drained the oil, hardly any came out, about .25qt if that...Dark, no shavings, just really burnt and thinned out...Radiator coolant level and color is fine...

Started right up, once again is just loud and blowing smoke, but revs good, runs good...So Grey, you think it's the piston/rings, but that just seems strange to me with only 20 hrs on it, 20 pretty mellow hours, except for some sand time, with oil changes/maint after every couple hours...

What other things would make it burn up so much oil???

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In order for the engine to burn oil, it has to get into the combustion chamber. There are a limited number of ways for this to happen:

  • Overfilling the engine: If you don't completely drain the engine, and/or you add more than 1 liter back, there's too much oil, and that causes the level in the sump to be too high, since there's no room in the tank for the excess. That in turn causes there to be more oil on the cylinder walls than the rings can control. But as mentioned earlier, once it burns down close to the correct level, it stops, and there is no noise associated with it.
  • Head Gasket: Since oil pressure passes through the cylinder deck to get to the head, there is a potential leak at the right rear corner of the head. However, if this were to be leaky enough to allow oil into the chamber, it would almost certainly show up as combustion gas in the cooling system, and cause coolant out the overflow and overheating.
  • Porosity in the head or cylinder: Just possible. Extremely unlikely.
  • Valve guide seals: Missing, damaged, or worn.
  • Failure of the piston rings to seal: Can be caused by wear, damage to the cylinder plating, rings, or piston. If the piston is damaged, it will likely "slap", creating a rattle noise as it goes over top.

The noise may not be associated with the oil consumption issue at all, either, and could be another problem, like a loose drive gear or a bad cushion unit in the basket, or a rod bearing, or it could just be normal.

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my guess rings - although 20hrs is nothing unless a lot of trash has been sucked through the carb.

also when have you repacked the muffler?

I would tear it down if it was mine before you get a very very expensive surprise

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Haven't repacked the muffler, again, only about 15 hrs on that pipe...

This bike is damn near new, and has been kept in pristine condition...

Most of who I've talked to so far say valve seals and piston rings...

I'll open it up this weekend...

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For it to be doing that at 20 hours, something is wrong. And thick at that. There is no reason why it should be that bad that early.

How often do you change the oil, and lube the filter?

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For it to be doing that at 20 hours, something is wrong. And thick at that. There is no reason why it should be that bad that early.

How often do you change the oil, and lube the filter?

Exactly...I change the oil every ride day at the track, and every 4 hrs leisure riding...Clean and lube the air filter after every wash, which is usually the same as the oil...

I got one of 2 that were left at the dealer after the 08's were already out for a while...Got a smoking deal...Haha get it, a "smoking" deal? I actually thought it sounded loud from the get-go but was told by everyone, don't worry, these yz's are super loud like that especially the 07's, then I threw a pipe and carbon fiber skidplate on and it got really loud, made it hard to compare with some other yz's but I did and it was slightly louder but not much...

Anyway the cam chain and tensioner needed to be replaced almost right away "for some strange reason it was faulty"...

Now it's burning through one liter of oil in a couple of hours, but runs fine besides being loud and belching smoke...What gives? Did I get a mellon? Keep in mind I've been maintaining my dirtbikes for 20 years, have been riding dirt all my life, rode street for a few years, my 97 KX250 runs flawlessly...

I just hate getting a brand new bike, then having to go through a bunch of issues before it's truly reliable...

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Exactly...I change the oil every ride day at the track, and every 4 hrs leisure riding...Clean and lube the air filter after every wash, which is usually the same as the oil...

I got one of 2 that were left at the dealer after the 08's were already out for a while...Got a smoking deal...Haha get it, a "smoking" deal? I actually thought it sounded loud from the get-go but was told by everyone, don't worry, these yz's are super loud like that especially the 07's, then I threw a pipe and carbon fiber skidplate on and it got really loud, made it hard to compare with some other yz's but I did and it was slightly louder but not much...

Anyway the cam chain and tensioner needed to be replaced almost right away "for some strange reason it was faulty"...

Now it's burning through one liter of oil in a couple of hours, but runs fine besides being loud and belching smoke...What gives? Did I get a mellon? Keep in mind I've been maintaining my dirtbikes for 20 years, have been riding dirt all my life, rode street for a few years, my 97 KX250 runs flawlessly...

I just hate getting a brand new bike, then having to go through a bunch of issues before it's truly reliable...

Does it smoke more when gassing it, or when decelerating/downshifting?

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Does it smoke more when gassing it, or when decelerating/downshifting?

when giving gas...

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Rings.

Bingo

Edit: Lets see some pics of the carnage when you get her popped apart

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Ditto to the above. Mabe the rings weren't gapped properly and are broken? Bad cylinder wall?? Should be torn down before something really bad happens. Piston, rings and gaskets are cheap compared to heads, bearings and cranks ect. ect.

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Alright, I'm going to start opening it up today...

I've never done this on a thumper (have rebuilt a few old school 2 strokes).

I'm just going by the service manual, and will be taking photos and notes along the way to share with other people on here...Hopefully to be a "how to change the piston and rings" thread, and not a "why you should only let experienced mechanics work on your bike" thread...

ANY HELP OR TIPS BEFORE OR DURING ARE GREATLY APPRECIATED!!!

I'm crossing my fingers that the cylinder wall is fine...I plan on putting in a new piston and rings no matter what, sorry but I don't want to go through all that labor and not improve the bike......I know Wiseco has gotten a bad wrap on here (I feel is slightly unjust)...What would you recommend? High compression? Obviously I'll wait to order until I see the cylinder wall...And do I need to pick up a valve spring compressor and piston pin puller?

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