'08 450 with 47 hours = locked up :(


104 replies to this topic
  • swaldrop

Posted May 25, 2008 - 06:41 PM

#61

I can vouch for the reliability of the Yami thumpers as I had a 400 and was very reliable but....

Dont listen to 5 or 6 tards on here who get 50, 100, 150, 200 hours on stock valves and brag about it. I call them out from time to time and usually get bad gas for it. My condolences man, I hate to see this kind of stuff. Hopefully you can get it warrantied like KAS. This is what can happen with the new generation of thumpers. Great power for a price:excuseme:

Good luck!


I appreciate the support, but I'm not sure where you were headed with that either. My bike has 47 hours on it.

  • dbehr624

Posted May 25, 2008 - 11:13 PM

#62

Man sorry to hear about that, best of luck with this whole ordeal and hope yamaha will take the bill.

  • motoclay

Posted May 26, 2008 - 08:09 AM

#63

Why do u not lap titanium valves?? what makes them so special??? I dont care what valve it is, if it is not lapped to the seat it cannot seal properly??

Ne way, yeah, a grand will probably get you back underway. One other MAJOR thing u need to do, is find all the metal that is missing!!! All the slivers and chunks, they are in the crank case, or on top, my motor when this happend, had a hole in the piston where the valve stem whent through it, i found the piece that made the hole in the bottom of the crankcase.

Like i have said many times already, INSPECT-CLEAN-INSPECT-CLEAN-INSPECT AGAIN.

Just to kinda give you a suggestion as to what could have been your cause of failure. My 450 blew the head gasket first! After thinking about it a while, thats what caused the valve to drop. The steam that was being created made it much hotter and just torched the tulip off. I never asked it was an intake or exhaust valve that failed. It was an exhaust valve could be runnin a little lean, a little lean and on the gas hard will build one hellofa fire in the cylinder creating some mean heat, and enescence causing the torch effect i mentioned that will just slice that bad boy off right at the stem.

ONE OTHER Thing lol. Sorry, i just feel like i need to spill my beans on what i know bout this.

The reason i wouldnt consider a rebuild HEAD is this. The heat that is created in this part of the engine is rediculous. If there are pieces welded in or melted back in to fill holes and so forth, IN MY OPINION could get hot enough to fall out, one other thing with it too, is ne sharp edge sticking out will get really hot, like a spark plug tip, it will cause detonation, like running cheap gas. Basically PRE LIGHTING the fire.

ALL OF ABOVE IS MY OPINION/EXPERIENCE, WITH THIS ISSUE, PLEASE DO NOT THROW STONES!!!

  • Ga426owner

Posted May 26, 2008 - 08:28 AM

#64

I can vouch for the reliability of the Yami thumpers as I had a 400 and was very reliable but....

Dont listen to 5 or 6 tards on here who get 50, 100, 150, 200 hours on stock valves and brag about it. I call them out from time to time and usually get bad gas for it. My condolences man, I hate to see this kind of stuff. Hopefully you can get it warrantied like KAS. This is what can happen with the new generation of thumpers. Great power for a price:excuseme:

Good luck!



and you must be the type of rider that rides a little too often on the rev limiter......huh? 50-100hrs is very very easy to achieve with stock valves if you do not abuse the motor

  • swaldrop

Posted May 26, 2008 - 08:49 AM

#65

Why do u not lap titanium valves?? what makes them so special??? I dont care what valve it is, if it is not lapped to the seat it cannot seal properly??

Ne way, yeah, a grand will probably get you back underway. One other MAJOR thing u need to do, is find all the metal that is missing!!! All the slivers and chunks, they are in the crank case, or on top, my motor when this happend, had a hole in the piston where the valve stem whent through it, i found the piece that made the hole in the bottom of the crankcase.

Like i have said many times already, INSPECT-CLEAN-INSPECT-CLEAN-INSPECT AGAIN.

Just to kinda give you a suggestion as to what could have been your cause of failure. My 450 blew the head gasket first! After thinking about it a while, thats what caused the valve to drop. The steam that was being created made it much hotter and just torched the tulip off. I never asked it was an intake or exhaust valve that failed. It was an exhaust valve could be runnin a little lean, a little lean and on the gas hard will build one hellofa fire in the cylinder creating some mean heat, and enescence causing the torch effect i mentioned that will just slice that bad boy off right at the stem.

ONE OTHER Thing lol. Sorry, i just feel like i need to spill my beans on what i know bout this.

The reason i wouldnt consider a rebuild HEAD is this. The heat that is created in this part of the engine is rediculous. If there are pieces welded in or melted back in to fill holes and so forth, IN MY OPINION could get hot enough to fall out, one other thing with it too, is ne sharp edge sticking out will get really hot, like a spark plug tip, it will cause detonation, like running cheap gas. Basically PRE LIGHTING the fire.

ALL OF ABOVE IS MY OPINION/EXPERIENCE, WITH THIS ISSUE, PLEASE DO NOT THROW STONES!!!


No stones. Whether I can use it or not, I appreciate any real world experience on this particular issue :thumbsup:

Other than the few indentations from the broken valve, the top of the piston looks good. Not a whole lot of material missing. I believe everything was contained to the area above it and I have completely removed all affected parts.

The valve that broke was the right intake. I am no jetting expert by any stretch of the imagination, but as far as I could tell it was jetted pretty well. Stock jetting here in Florida always seems to work pretty well. A couple quarter turns in or out with the fuel screw, depending on how hot it was that day, always seemed to make it run perfectly. The head gasket is still in great shape as well.

Without doing any research yet, I am assuming that 'lapping' valves simply means to shape them a bit to seal tight in the valve seat, no? If no lapping is required, am I to assume that any OEM Ti valve will seal perfectly into any new OEM head? And if this is only true for Ti valves, what if I went with some after market stainless valves? would they then need to be 'lapped'? If so, how does one go about lapping valves?

I tend to agree with you on the head rebuild, but I am going to look into it any how. If someone who knows more about the process can explain to me just how it's done and I am comfortable with it, I'll do it, so long as the savings are there. I certainly wouldn't prefer a rebuild dollar for dollar.

Again, thanks to all for shedding some light on this deal. I have already learned a great deal, and after all is said and done I am sure I will be all the more wiser (and much lighter in the wallet).

  • motoclay

Posted May 26, 2008 - 09:35 AM

#66

Lapping valves is just a process of finely sanding it to fit. U use a compound u get at a parts store its a grease based product. U put a very small amount on the valve tulip where it touches the seat, and spin the valve/twist the valve with the lapping tool to MATCH the surfaces.

  • grayracer513

Posted May 26, 2008 - 09:44 AM

#67

Why do u not lap titanium valves?? what makes them so special??? I dont care what valve it is, if it is not lapped to the seat it cannot seal properly??

Titanium is very strong, but not very hard, and ti valves depend entirely on an extremely thin (as thin as .003mm (0.00012") or less) coating of titanium nitride, or other related compounds for the hardness that enables them to last for any length of time whatsoever. Lapping, the process of spinning the valve against the seat with an abrasive paste applied, wears against this coating. The coating is exceptionally hard, but due to its thinness, it is extraordinarily unwise to lap titanium valves.

In any case, the valve is a precisely machined part, and if the seat is ground correctly, there is no need to lap them to improve the fit or seal.

  • swaldrop

Posted May 26, 2008 - 10:29 AM

#68

Titanium is very strong, but not very hard, and ti valves depend entirely on an extremely thin (as thin as .003mm (0.00012") or less) coating of titanium nitride, or other related compounds for the hardness that enables them to last for any length of time whatsoever. Lapping, the process of spinning the valve against the seat with an abrasive paste applied, wears against this coating. The coating is exceptionally hard, but due to its thinness, it is extraordinarily unwise to lap titanium valves.

In any case, the valve is a precisely machined part, and if the seat is ground correctly, there is no need to lap them to improve the fit or seal.


Would it a safe bet to assume that OEM valves and Heads match up accordingly?

  • grayracer513

Posted May 26, 2008 - 10:48 AM

#69

Yes, it would.

When assembling new valves into a new head, I like to tap on each valve stem with a punch just hard enough to bounce them off their seats a time or two. This settles the keepers, and the entire rest of the assembly, and makes your initial valve clearance check more accurate. Before installing the head, I solvent test both ports to assure that the valves seal.

  • swaldrop

Posted May 26, 2008 - 10:51 AM

#70

Yes, it would.

When assembling new valves into a new head, I like to tap on each valve stem with a punch just hard enough to bounce them off their seats a time or two. This settles the keepers, and the entire rest of the assembly, and makes your initial valve clearance check more accurate. Before installing the head, I solvent test both ports to assure that the valves seal.


Solvent test?

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  • grayracer513

Posted May 26, 2008 - 11:00 AM

#71

With the head positioned so that one of the ports is facing up, pour clean solvent into that port of the assembled head to test whether the valves seal well enough to hold it. With brand new parts, only a very slight seepage should occur, if any at all.

  • motoclay

Posted May 26, 2008 - 11:29 AM

#72

Titanium is very strong, but not very hard, and ti valves depend entirely on an extremely thin (as thin as .003mm (0.00012") or less) coating of titanium nitride, or other related compounds for the hardness that enables them to last for any length of time whatsoever. Lapping, the process of spinning the valve against the seat with an abrasive paste applied, wears against this coating. The coating is exceptionally hard, but due to its thinness, it is extraordinarily unwise to lap titanium valves.

In any case, the valve is a precisely machined part, and if the seat is ground correctly, there is no need to lap them to improve the fit or seal.


I would still lightly lap it. There should be NO seapage of liquid through it, i mean if u are trying to build a high performance motor, seapage means loss of compression! Less HPs

  • motoclay

Posted May 26, 2008 - 11:31 AM

#73

not to mention, if it does not seal u can potentially burn a new valve right away! Just lap the valve!! that doesnt even make sense not to lap it. U dont freakin grind it for days, just a light little buff is all it needs, but it MATCHES teh surface for a perfect, HIGH PERFORMANCE fit!

  • bigred455

Posted May 26, 2008 - 12:02 PM

#74

I have always heard and read on here not to lap titanium valves. The YZ450 F MANUAL instructs to lap new valves to the seats ,states it right in your service manual. I am starting to think it is a old myth not to lap titanium valves.:thumbsup:

  • motoclay

Posted May 26, 2008 - 01:06 PM

#75

yeah, i would think its a MUST for proper seal. I was lookin for an online manual to read it myself, but its just crazy NOT to lap them. IMO!

  • grayracer513

Posted May 26, 2008 - 01:30 PM

#76

Lapping is the old myth. It's unnecessary and dangerous with ti valves. The suggestion in the manual that they should be lapped is a carryover from the steel valve days (when it was also unnecessary).

By slight seepage, I mean that the joint at the valve seat will exhibit wetness after a few seconds. Nothing more. That will disappear in the first 2 minutes of run time. The idea that there is any risk of burning a new valve as a result is just silly.

But they're your $85 valves. You can do what you want with them.

  • TD-3

Posted May 26, 2008 - 02:33 PM

#77

If this head will fit, it will save you a little money.

http://cgi.ebay.com/...sspagenameZWDVW

  • 2strokenut

Posted May 26, 2008 - 03:09 PM

#78

And your point is what?


Just because a few people have gone so long on stock valves doesnt make it smart for someone to go 47 hours without at least checking the vlaves:excuseme: I thought my point was pretty clear.

I appreciate the support, but I'm not sure where you were headed with that either. My bike has 47 hours on it.


Like I said above, going that long without checking to see if clearances were in spec is not smart. People make the yami 450 out to be some sort of blue XR, which is not the case. The motor will run for a long time with simple maintenance but when something goes wrong is not a simple or cheap fix.

and you must be the type of rider that rides a little too often on the rev limiter......huh? 50-100hrs is very very easy to achieve with stock valves if you do not abuse the motor


No I mix my gas. Dont abuse the motor? Dirt bikes are meant to be abused (ie ridden hard, revved ect) and Im not gonna buy a bike where I have to ride like a pus to get engine longevity. I agree 100-150 hours is easy, had that much on my 400 at least. But that was stupid on my part.

  • swaldrop

Posted May 26, 2008 - 03:32 PM

#79

If this head will fit, it will save you a little money.

http://cgi.ebay.com/...sspagenameZWDVW


Thanks for the heads up. I actually saw that last night and sent a message to the guy asking about what year it is for. I have yet to get a response, but if it is what he says it is, it's a great deal.

Thanks again

  • swaldrop

Posted May 26, 2008 - 03:37 PM

#80

Just because a few people have gone so long on stock valves doesnt make it smart for someone to go 47 hours without at least checking the vlaves:excuseme: I thought my point was pretty clear.


Like I said above, going that long without checking to see if clearances were in spec is not smart. People make the yami 450 out to be some sort of blue XR, which is not the case. The motor will run for a long time with simple maintenance but when something goes wrong is not a simple or cheap fix.



As I have said before, there was no indication from the motor that a valve was suspect. It ran perfectly. If the valve was out of adjustment to the point of it causing a major failure, then I would have had some other indication, no?





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