Head and Piston advice for the 80cc

[phatmanxxl]

Been blowing white smoke and still can't break 30mph. Last time I looked at the valves they were pretty crusty and new heads being less than $30 I'll probably order a new one.

I'm looking at the one with 69mm valves, is the the one I should get? Will it effect the timing chain? Its already tight, any tighter and it'll probably snap. I already have a A9 cam (didn't work with the stock head) or should I keep the stock.

Just looking for advice before I start buying stuff.

[badpumpkin]

I understood that white smoke is un combusted, and black smoke is combusted. With that said I would think that you might have valve or gasket issues.

[phatmanxxl]

If it was the gasket I would probably be leaking oil, I'm convinced the valves went bad. I'm just asking if there's more to it than just buying the head, like do I need new rocker arms too? Chain?

[90GTVert]

Have you checked out your cylinder and piston rings? Could be oil sealing issues there. Possibly bad valve stem oil seals. You may be able to look in the ports for evidence of oil passing down the valve stem toward the cylinder.

Most just go with whatever valve length they currently have. You can swap rockers if you want a head with a different length of valves. Info :

[phatmanxxl]

I maybe have 500 miles on the new piston and rings, like I said the vales were covered in carbon when I put the bike back together so I'm thinking that could be the issue. My bike will be out of service for the weekend so I'll check out the piston rings when I get the chance.

[phatmanxxl]

[phatmanxxl]

Its pretty bad, spent a good few hours scrubbing the carbon off.

Are you suggesting I re-dial my piston rings? This BBK is probably a month or so old so I would hate to think the rings are bad.

[jkeney]

Your rings are toast from where I am sitting! Rings are super cheap though.

[jkeney]

I have eased up and started breaking in engines softer after this has happened to me a few times in a row. And I think part of my change that made the biggest difference would be running the break-in oil longer and the first oil change is break-in oil as well. I think I was burning rings from synthetic to soon.

[jkeney]

Actually looking at it again it looks like valve seals. Take a pic of the side of the piston, and pics of the valve stems inside the intake and exhaust ports. A pic of these should be pretty obvious to tell from.

[jkeney]

I hate those thick head gaskets too btw!
Those gaskets deff drop compression.

[phatmanxxl]

Oct 22, 2016 20:46:27 GMT -5 jkeney said:

Actually looking at it again it looks like valve seals. Take a pic of the side of the piston, and pics of the valve stems inside the intake and exhaust ports. A pic of these should be pretty obvious to tell from.

The insides of the valves have a little deposit, hardly any. I cleaned it up the best I could, what's left is really stubborn but I don't want to damage the valves. I'll take a pic of the piston tomorrow. 

Yea I used synthetic when I did the break in, maybe thats where I went wrong.

[dexameth]

How did you clean the carbon off? I was just about to start a thread asking and I stumbled onto this one. I pulled my spare motor apart today and this is what I found:

[phatmanxxl]

I used oven cleaner to break it down (let it soak), a firm plastic brush and an abrasive sponge to scrub it, break parts cleaner to rinse it off. Repeat.

Yours isn't as caked on as mine, it shouldn't be to difficult to clean it up in your case.

[jkeney]

Synthetic will burn the rings up during break in. If there is discoloration below the rings then you are getting blow by.