Does this head need to be repaired?

[Premixer112]

I'm doing my winterly top end, and I just got my cylinder back from getting replated for the second consecutive time, and the guy that sent it off for me was saying that reason I was having issues was probably that I didn't use the air filter oil that you pour on, but rather the aerosol stuff. But I also am wondering if it's because of the head. Maybe you guys can give me an opinion on this. The majority of the center of the combustion chamber looks fine, but does that outside ring have any effect on the way the engine runs or the longevity of it?

 

 

 

[big man bren]

you sure you dont got a chunk of ring or dirt in your top end looks like its been been eaten away

 

try finding a used head on ebay or something id probably replace it (if it wer me) 

[563ripper]

does the very top of the cylinder look eaten away like the head?

[slomojo]

Looks like something got real abrasive or real hot or a combination of both.It looks like toast to me eroded in the squish area like that.

[Bremer120]

My 05 head looked similar to that. Yours is more severe and I think would need welding. I was really worried about mine because it had small holes and the base of the head was eaten away slightly but my machinist assured me it was ok. I would definitely weld or replace yours. I think it could generate hot spots easily.

[Bremer120]

Actually I think you would blow the inner o-ring quickly with how chewed up that is

[Bremer120]

Actually I think you would blow the inner o-ring quickly with how chewed up that is

[MANIAC998]

Actually I think you would blow the inner o-ring quickly with how chewed up that is

I'm wondering if the inner o-ring is already leaking and caused this? In the one photo you can see how it doesn't seem like it's sealed all the way around 360 degrees.

[Premixer112]

Alright, I'm glad I decided to come on here for some reassurance haha. I will definitely get it repaired or find a new one. I looked on ebay, but there aren't any for sale past around '98 for the yz250's. What would be the better thing to do, send it off somewhere or keep looking for a used head? And where is the best (and quickest) place to send it to?

[Bremer120]

I'm wondering if the inner o-ring is already leaking and caused this? In the one photo you can see how it doesn't seem like it's sealed all the way around 360 degrees.

Yeah I saw that there was a lil spot where the seal quit holding

[Bremer120]

Alright, I'm glad I decided to come on here for some reassurance haha. I will definitely get it repaired or find a new one. I looked on ebay, but there aren't any for sale past around '98 for the yz250's. What would be the better thing to do, send it off somewhere or keep looking for a used head? And where is the best (and quickest) place to send it to?

I scoured ebay for a few weeks looking for a replacement and all I found was a 99' head and since it had a different number cast on it I passed on it and just ran mine. Personally I would have it welded and recut. I'm not sure who would do the work for you. Try rb?

[BDubb106]

I'm wondering if the inner o-ring is already leaking and caused this? In the one photo you can see how it doesn't seem like it's sealed all the way around 360 degrees.

Exactly what it looks like to me.

 

OP: Have you noticed your coolant level dropping at all?

Edited February 18, 2014 by BDubb106

[Premixer112]

Exactly what it looks like to me.

 

OP: Have you noticed your coolant level dropping at all?

You know what, I think I've seen small drops over time and my bike would kind of do that "stumbling" thing in it's idle after riding for about 15 mins or so hard. 

I scoured ebay for a few weeks looking for a replacement and all I found was a 99' head and since it had a different number cast on it I passed on it and just ran mine. Personally I would have it welded and recut. I'm not sure who would do the work for you. Try rb?

What's RB?

[BDubb106]

You know what, I think I've seen small drops over time and my bike would kind of do that "stumbling" thing in it's idle after riding for about 15 mins or so hard. 

What's RB?

http://www.rb-designs.com/

 

That is exactly what it looks like to me. Errosion from coolant.

[Zappa]

That head looks like it was damaged by detonation. Essentially under heavy load, the YZ engines are known to detonate, especially if using slightly bad gas. After the detonation wears the edge enough, the o-ring melts and starts leaking coolant.

 

Have you ever heard any rattling or knocking under heavy load?

 

Since you should fix the head in that condition, I would have RB Designs modify the shape a bit and cleanup the squish which should prevent any future detonation.

[Bremer120]

That head looks like it was damaged by detonation. Essentially under heavy load, the YZ engines are known to detonate, especially if using slightly bad gas. After the detonation wears the edge enough, the o-ring melts and starts leaking coolant.

Have you ever heard any rattling or knocking under heavy load?

Since you should fix the head in that condition, I would have RB Designs modify the shape a bit and cleanup the squish which should prevent any future detonation.

Agreed. You can measure the head in the condition it's in and get pretty darn close and see if rb could do the whole treatment to it.

[souliog]

pitch that head in the garbage can and buy a new one...$212 @ Motosport.com

[Premixer112]

pitch that head in the garbage can and buy a new one...$212 @ Motosport.com

Why would I do that when I can have it repaired for much less??

[souliog]

You can spend $100 to repair, but I would worry that there isn't enough material left for the water jackets. Then you will waste the money for nothing.

 

The guy repairing the head will tell you it's ok and he does it all the time.

[intensem1rider]

I would definitely recommend getting the squish clearance set properly and set the timing properly.  I believe the general consensus is 1 deg retarded on a stock 250??