Getting valve seats recut

[CRFRichard]

Hello everyone, I was hoping someone with some extensive mechanical prowess can take a gander at this picture of my CRF450R exhaust valve seat damage.

Is this damage repairable?

Would oversized valves be a good recommendation to fix this?

Or, should I hunt for a new head?

Thank you very much.

Edited January 11, 2017 by CRFRichard

[m78val]

You could have seats and valves installed, oem honda heads can be had for 500 to 800 complete, it is repairable, try afe, fast heads or crf's only,pretty reasonable prices for complete heads, hopefully this helps

[CRFRichard]

m78val, would cutting the seats for oversized valves be considered a good fix for this? That's what my local moto shop is suggesting. I've never cut seats oversized before. What else might I have to upgrade for such a job?

[turbo dan]

Seems to be a good size chunk of material missing?  I don't even know if theres enough meat left to even go oversize at all, let alone consider that a fix.  Also consider the possibility that the seat may have become brittle from stress and heat cycles, which would make it more likely to continue to crack pieces off and drop them into your motor.  That is an exhaust valve seat and they do run hot.

[CRFRichard]

turbo dan, haha my bad that is the exhaust valve seat! I edited my post to indicate that. Thanks for the correction.

So, would it be wise to just get a new head?

[jblob]

I would think so. Like he said new heads for crfs are surprisingly cheap. You get get them complete with everything installed ready to bolt on in the 5-600 range. Even if that head could be saved it is old and tired. Intake valves are probably getting cupped by this point. Not worth spending the money twice

[96motorhead]

I would buy a new head.

[CRFRichard]

I'll start looking for another head assembly. Thanks for the advice everyone.

[Fenmore]

What year is the bike? Original head?

[mxaniac]

Some people contend that welded heads have less inherent stress in them.  The argument is that during cooling a casting builds up internal stresses because of the thermal contraction not happening all at once in a rather thick component.

 

People can spew all sorts of theories that sound good.  Take this one for example, the Buffalo theory.  A herd of buffalo can only move as fast as the slowest buffalo. And when the herd is hunted, it is the slowest and weakest ones at the back that are killed first. This natural selection is good for the herd as a whole, because the general speed and health of the whole group keeps improving by the regular killing of the weakest members.In much the same way, the human brain can only operate as fast as the slowest brain cells. Excessive intake of alcohol, as we know, kills brain cells. But naturally it attacks the slowest and weakest brain cells first. In this way, regular consumption of beer eliminates the weaker brain cells, making the brain a faster and more efficient machine. That’s why you always feel smarter after a few beers.”  Sounds quite plausible doesn't it!

 

I took the bait once and had some cracked Subaru heads repaired, in my case it turned out to be a bunch of B.S.  The welded heads cracked immediately.  I wouldn't try getting a crack in a head welded up.

[trvshonda]

Just needs new seats. Send it out to eric gorr or some other engine builder and have the seats cut out and new ones installed. Then new valves to top it off and it will be good as new.

[CRFRichard]

@Fenmore, the bike is a 2004 with the original head assembly.

@mxaniac, I definitely don't intend to get any cracks welded. The moto shop mechanic said his machinist might cut the seats for oversized valves, which may include cutting out that damaged area. However, the guy I spoke to isn't a machinist, so he could just be using his imagination for what he thinks might happen according to all his years as a mechanic (which is probably not very many).

@trvhonda, do you think it would be wiser to spend the money to refurb the old head or invest in a new one for more money?

[Jeff@bigborethumpers]

Head is fine. may want a valve job to clean up where that debris exited the motor, but the chips are common. it doesn't go into the 45* sealing surface. Or bigborethumpers.com offers new heads for $549.95 

Thanks

Jeff@APE

[m78val]

Realistically the head is salvageable, you could get seats installed and new valves or for the new head option, it's up to you, both are viable options, I had a an 04 crf and had the head done a few times, they had a few problems with valves cupping, not sure if it was because seats and valves material were softer or harder than the other, but I did have issues, good luck

[96motorhead]

I just talked to a honda tech last week about rebuilding heads. He said he's done hundreds of them over the years but he still recommended that I just buy a new head.

[HRC27]

Realistically the head is salvageable, you could get seats installed and new valves or for the new head option, it's up to you, both are viable options, I had a an 04 crf and had the head done a few times, they had a few problems with valves cupping, not sure if it was because seats and valves material were softer or harder than the other, but I did have issues, good luck

The early bikes had harder seats if I'm not mistaken, causing the valves to get beat up and cupped.

Pro1 uses copper alloy seats and claim they last 8x longer.

[CRFRichard]

I guess I'm just going to wait and see what my local moto shop mechs say once the machine shop receives the head. If they give me some off the wall fix, I'll just get a new head.

[notoriousE-R-I-C]

Thats just a valve sEAT! Why not get new valve seats? Stock size or over size? Dont even need a new valve looks like. Just get a matching 3 angle cut job to valves and seats, who does that will press the new seats in for you.

Buy a new head! Hahahahaha! That head holds a few more wins.