scratches on the cylinder head...

[VenomRS4]

So ive started the rebuild of my yz125 motor and have a question. The combustion chamber has a couple scratches toward the side of it. I brought my cylinder to th shop to have it bored and re-sleeved. I mentioned the scratches on the head and showed him. He said I need a new head. But the scratches arent that bad so I dont see how it will cause problems. I want more opinions on it.

Here is a picture, let me know what you think.

 

[2strokerfun]

I'm not sure I'd classify a couple of those as a "scratch." Did you lose a needle in a rod bearing?
You can probably lightly smooth them and use it, but I'd probably replace it. If this is a 92, it won't be much longer until you might not be able to easily find parts. So I'd get one now if the part is questionable.

My 2.3 cents (inflation and all)

 

[BigRedAF]

Any good shop can fix that. From the pic I would probably cut that head .020 and then re cut the squish area to the original angle. It will clean up nicely.

After you check the price for a new head call Pro Circuit and get a price for their head mod. They cut and re shape the squish all the time on their 2 stroke mods. If they happen to have an old 92 YZ head on the shelf they might cut you a deal, never hurts to ask...

 

[griffbones]

Pro Circuit would be good for sure, but I'll just bet that Eric Gorr would be cheaper and do every bit as good of a job as Pro Circuit.
In fact I would have sent the whole top end to Eric, as most shops (dealerships) send these kinds of things out anyway, so you don't really know who is working on your parts.

 

[whenfoxforks-ruled]

Sending the head to Eric would be way better than PC! Did them dents come from a circlip?

 

[Studboy]

If you are short on cash just sand down the scratches so that there aren't any sharp raised points (they cause pre-ignition) and you will be fine.

Over time they will fill in with carbon.

 

[VenomRS4]

Yeah, I want to keep this somewhat cheap. I dont want to spend any more on machine work than i have to. Its friggen expensive. I'll try to sand it down the best i can and then we'll see what happens.

 

[griffbones]

Did you know that the average cost of having a head cut is only $50 - $75.

 

[tony91]

If you are short on cash just sand down the scratches so that there aren't any sharp raised points (they cause pre-ignition) and you will be fine.

Over time they will fill in with carbon.

I had the same issue when I blew up an old CR250. I had to pump a bunch of cash into it and didn't want to replace the head. I asked Gorr about it and he suggested just what Studboy has. I ran it for a couple years before selling it with no issue whatsoever. Wash that thing with dish-soap and warm water when you're done sanding. Dry it with a clean paper towel to check for residue.

 

[BigRedAF]

Pro Circuit would be good for sure, but I'll just bet that Eric Gorr would be cheaper and do every bit as good of a job as Pro Circuit.
In fact I would have sent the whole top end to Eric, as most shops (dealerships) send these kinds of things out anyway, so you don't really know who is working on your parts.

You are correct Sir Bones :cool:

Eric has done work for me in the past and I was very satisfied.

 

[Tyler125]

I dont want to hijack this thread at all, but I dont want to start another one on the same topic. I have a 93 CR125 head that is scratched up a little more than the OP's head. Will it still be ok if I do the sanding trick? I would post a pic but it wont let me.

 

[whenfoxforks-ruled]

You do know that the price on a new head is under 100 dollars? Shipping and modifications is about the same. Carbon build up is not something to be fond of, it is very bad. It reaches and holds a LOT higher temperature than the surrounding area. If you are set on fixing yourself, all you are going to do is knock off high ridges that can fall off. Removing material usually requires reshaping the dome, squish band and mating surface.

 

[Tyler125]

Can you point me in the direction of oem heads then.I cant find a place to buy them online.

 

[tony91]

Service Honda is solid.

 

[AV8R]

I would sand it and use it for a 93. Not worth the investment for a new head.

 

[whenfoxforks-ruled]

A second vote for Service, honda, kawasaki, suzuki and yamaha! You may find parts on fleabay, good luck with whatever they claim and you get. But it is cheap.