2011 YZ450 valves out of spec at 76 hours

Hi guys

I was riding my bike yesterday training for a 6 hour long cross country race coming up in 2 weeks and near the end of the day my bike started to get really loud in the engine, so I turned around and babied the bike back to my truck and shut it down to let it cool down.

After awhile I decided to investigate if the noise was still there or if it was just me being me and worrying over my pride and joy haha. So I went to try and start my bike and found I had no compression and could just push the kick start lever all the way through the stroke with my hand, I packed up and loaded the bike straight after I found that out and went home.

When I got home I washed the bike and then blew it dry (as I always do after washing it) with compressed air and parked it up for the night to inspect it the next day. I started with the most simple things as checking if the spark plug had not come loose but it was in tight, so I then went to the next step. I removed the cam cover and inspected the clearances on the valves and got a shock to find that all but 1 exhaust valve was out of spec.

My one intake valve was so tight that I could not even get a 0.04mm feeler gage in and the other intake valve was 0.20mm clearance (spec is between 0.10mm - 0.15mm for intake) as for the exhaust the one was in spec at 0.23mm but the other one was out at 0.30mm. I had checked my valve clearances 10 hours before this happened and they had still not moved from factory from when I replaced the piston and rings at 66 hours. The timing was all still 100% correct as i also fitted a new cam chain while i was in there for cheap assurance.

I have taken the bike to the dealers and asked them to have a look and see what has happened as they told me that it is the first time they have heard of this happening is only 76 hours engine time..... like they always say haha.

I am very good with maintenance (even the ex can agree on that... haha) and my mates always joke and tell me that I almost do over maintenance as the bike and air filter is cleaned after every ride and I change the oil every 6 hours with a new OEM oil filter. I use Motul 300V engine oil and Motul air filter oil as I believe what you put in is what you get out.

So the question is, has this happened to anyone else at the amount of hours that I have ? as I have always been told that Yamaha is very good in regards to valves.

I haven't put many hours on my 2012 yet but from previous experience and knowledge of valves, They should be brought back into spec and checked again shortly after to see if they have changed. And the goal is to be in the middle of the spec, if its .10-.20mm then u want to be at .15mm. Like for example you have a valve that is too large of a gap, that needs to be brought back into spec to prevent excessive wear and make the valve open up enough

Edited by laudy152

Its not often that the gap gets wider. :mellow: But I agree with the last post. Just shim it up so that ur in the middle of the range and keep any eye on it. Valves move. Its that simple, its not a terrible thing. The harder u ride the more often u should check them. what was the spec at 67 hrs when the piston and timing chain was done?? who did the work??

Hi guys, thank you very much for your answers and advice, I have worked on 4 strokes before and have been rebuilding my own engines for a few years now.

The shop mechanics and store owner told me that i caught the valve that has zero air gap just before it was about to let go, so he said i was lucky in a way to just shut it down and park it.

as for spec's for the air gap the intake is between .10mm - 0.15mm and the exhaust is 0.20 - 0.25mm, so for both intake and exhaust there is only 0.05mm to play to be in spec (if I am reading it correctly) as per the workshop manual for my bike that i have and follow like a bible.

The valves were all in spec as per the manual at 66 hours (forgot to mention that) as i checked them while i was tearing it down to fit the new piston and rings, I did all the work myself. I do ride my bike hard as i do a lot of cross country racing but that is why I am almost OCD on preventative maintenance like checking the air gaps every 10 hours.

the valves were still in spec at 70 hours but between that and now 76 hours they just went awal, I had a fresh air filter for each ride Saturday and Sunday.

I just find it weird that some of the valves air gap got larger and the one valve just has no air gap from just 2 rides ? (3 engine hours per ride) I had the timing all correct and perfect as i took pictures of were it all must be as a ref. when it came to timing it while putting it back together.

The shop owner told me that the only people that he knows that have had their valves move this early are the guys he sponsors in the super motards with the same model as mine, but said his cross country guys have had them last for over 100 hours with not having to adjust. So he could not understand why mine have done this so early, but said that he will help me out with the repair as he wants me to race the 6 hour Iron Man race coming up.

Let us kno wat u find out. Im interested in knowing what is keeping ur valve from closeing all the way creating the gap. Or mayb the cam cap has issues allowing the cam to lift creating a loose condition on 1 valve and a tight condition on its neighbor.

Edited by mhebert68

On the valve that got larger, tap the lifter lightly so as to "bounce it shut", then recheck it. A carbon ledge at the stem where it meets the guide can hold it slightly off the seat sometimes as the engine is rotated slowly. If it hasn't changed, remove the exhaust cam cap and check it for having been seized. If that looks normal, proceed to remove the lifter and adjustment shim and inspect the condition of the top of the stem. There have been reports of the hard tip of the stem splitting and/or breaking off.

As to the intakes that have sunk, reshim them and check them again in 5 more hours or so. If they stay put, have another look in another 5 hours. If they stay, you're alright, if they keep closing up in that short interval, they need to be replaced because it means the hard coat is worn through on the valve face.

I just wanna say that I think 66 hrs is a little early for a topend I would think. Reason saying.....My 2010 had 68hrs on it when i sold it to my friend that owns the Yamaha shop and is the mechanic. he sold me a new 2011 model so I sold him my 2010. I raced my 2010 in MX for 2 years and practiced also. He raced with us this past year on the 2010 and it now has i believe he said 87 hrs on it.

He has'nt put a topend in it yet and said he was going to run several races with us this year. He said once it hits100hrs he might check it out. My 2011 has 36 hrs on it now and I checked the valves and all is good. We both use Amsoil and I change mine at about every 4 hrs.

I guess I will keep a look out on the valves every so often to make sure they dont tighten up but if they last as good as the 2010 did then I will be ok until i buy a 2014 off of him.

Just replaced top end, clutch, timing chain at 100 hrs. Everything measured in specs except for piston ( rings good). Really surprised me as I'm not always the easiest on a bike. Testament to yamahas reliability.

I just wanna say that I think 66 hrs is a little early for a topend I would think. Reason saying.....My 2010 had 68hrs on it when i sold it to my friend that owns the Yamaha shop and is the mechanic. he sold me a new 2011 model so I sold him my 2010. I raced my 2010 in MX for 2 years and practiced also. He raced with us this past year on the 2010 and it now has i believe he said 87 hrs on it.

I thought the same way with my first '09 yz450, they're super reliable right ? It's a Yamaha, it'll go longer than the other brands before needing a top end right ? Not so much in my case. Although my first '09 didn't suffer any catastrophic engine failure before I changed the top end at 100 hours, what did happen was the cylinder was damaged enough that it warranted replacement. I had a significant amount of ring float going on, you could see & feel where the ring had damaged the wall of the cylinder. It wasn't a huge deal, but it cost me another $260 (or something like that) for a new cylinder.

I'm on my 2nd new '09 yz450 and just replaced the top end in it at 75 hours, guess what.... no ring float and the cylinder looked great.

Keep in mind that I ride/race MX only, closer to the bottom of the B class pool.. I would suspect/guesstimate that trail riding etc. would put considerably less stress on an engine and you may see many more hours before you need to replace a top end.

Hey guys

Thanks for looking at this and trying to help were you can, as for trail riding I am constantly at high RPM as our race events are fast flowing and WOT at most points, I have had to gear my YZ to get 140km/h in 5th gear. At 66hr all the rings on my piston were at the limit (as in the manual) so this is why I changed them and the piston at the same time (was even using oil past the rings)

Anyway I have some photo's and an update on what me and a mate of mine have found on my bikes valves that have gone out of spec all of a sudden.

As the photo's below you can see that the one collet has come completely out of the retainer and was about to fall out completely, my mate (who is a qualified bike mechanic) told me to go buy a lotto ticket as I must be a very lucky man for catching this just before it dropped that valve. This explaines why that valve lost all its air gap so quickly.... but how this happened we do not know as I try not to hit my rev limiter as much as possible.

Has this happened to anyone else with a 2010 - 2012 or is this a S**t happens moment ?

I am replacing all 4 valves and 8 collets and also replacing the retainer that came off that valve with new stem seals.




Edited by kiwikawa

I havent heard of it, but ur right Sh it happens. Good call on replacing everything.

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