2006 ZS250GS

[m0t0]

[SpudRider]

Thanks for posting the photos, Moto. You definitely need a new cam sprocket. :( I strongly suspect you also need a new camshaft. Please post photographs of the end of the camshaft where the sprocket attached.

The good news is this; those parts are readily available for low cost from Taobao.

Spud

[m0t0]

Spud,

You must watch the forums like a hawk Sorry for the delay in getting those pics up. Real life got in the way. I will try to post pics of the camshaft tonight when i get home.

Thanks,
m0t0

[FastDoc]

Nasty.

[m0t0]

[SpudRider]

You definitely need a new camshaft. :(

Have you pulled off the cylinder head? I wonder if the piston hit the valves? If you choose to repair this engine you will need to remove the metal fragments which fell down the cam chain passage into the area around the flywheel. You will also need to get a slide hammer to remove the damaged camshaft. If you want to get an idea of some of the work involved, you might enjoy reading the following thread.

http://chinariders.net/modules.php?n...wtopic&t=14802

Spud

[m0t0]

New pics for all!

[m0t0]

correct me if i'm wrong, but it looks like i need a new head?

[katoranger]

Would it be possible to use a complete yamaha top end? Cylinder, piston, head?

[SpudRider]

Wow! 8O That's more damage than I expected! :?

Fortunately, you might not need a new cylinder head. As long as the inside diameter of the camshaft bearing has not been damaged, you can smooth out the damaged area of the outside diameter of the bearing. You can also smooth out the damaged area of the cyclinder head, since the camshaft only turns on the inside diameter of this bearing. If the inside diameter of the bearing is damaged, you can purchase a new bearing along with a new camshaft.

Weldangrind is familiar with a modification performed on TW200 cylinder heads, which should also work on your cylinder head. For this modification, you would once again smooth out the damaged area of the cylinder head which supports the camshaft bearing. Then you would install a sealed, ball bearing which has the same diameter for the inner race as the diameter of the camshaft. Once again, since the camshaft turns only on the inner race of the bearing, the damaged, outside diameter of the cylinder head is irrelevant.

However, it's important to keep a tight fit between the camshaft bearing and the cylinder head, so the camshaft won't wobble. If you don't want to perform either the repair I mentioned, or the modification, you will need to purchase a new, ZS250GS cylinder head. I don't think any Yamaha cylinder heads will work for your ZS250GS, since the Zongshen cylinder bore is larger than the XT225 cylinder. :?

Spud

[m0t0]

Any recommendations on an easy way to smooth that out? Maybe just sandpaper?

Thanks
m0t0

Oh, and on a side note that cam bearing it seized solid so it looks like ill be getting another one.

[SpudRider]

I would use a Dremel tool with a cutting wheel, and a magnifying glass. If you don't feel comfortable doing the job, I suggest you take the cylinder head to a machinist. I'm sure he will do the job properly for a modest cost.

Spud

[SpudRider]

Originally Posted by m0t0

Any recommendations on an easy way to smooth that out? Maybe just sandpaper?

Thanks
m0t0

Oh, and on a side note that cam bearing it seized solid so it looks like ill be getting another one.

The cam bearing doesn't cost much, especially if you get it from Taobao. Order the cam bearing along with a new camshaft, cam sprocket, and cam chain.

Did you check the valves and the piston head? Did the piston strike the valves and bend them? Is the piston head damaged?

Spud

[FastDoc]

The other interesting thing is that as bad as this damage is, I don't think it would have kept the motor from starting.

[m0t0]

The head of the piston looks fine but i will post some pics hopefully tomorrow. The valves also seem to be fine. I poured some gas in behind them and no leaks. I haven't pulled the valves out yet. Is this something i should do while I'm at it?

Thanks,
m0t0