S3 Head doesn?t fit?

[Dario]

Hi there,

I recently bought a S3 Cylinder Head for my GasGas EC 300 2014. Yesterday I went to install it after I got my cylinder back from coating and honing and noticed that the inner component didn?t fit into my cylinder.
Has anyone else had this problem or have I just gotten lucky with my purchase?
The Stock head fits perfectly fine.

[Anders]

Originally Posted by Dario

Hi there,

I recently bought a S3 Cylinder Head for my GasGas EC 300 2014. Yesterday I went to install it after I got my cylinder back from coating and honing and noticed that the inner component didn?t fit into my cylinder.
Has anyone else had this problem or have I just gotten lucky with my purchase?
The Stock head fits perfectly fine.

I have no experience with the S3 heads, but I see that they have several models. Are you sure you got the correct one for your year?

And secondly, are you sure that your bike is a 300? If you recently bought a secondhand bike, some previous owner might have converted it into a 250

[Jacob 'Berg]

Double check you did not purchase a head for the 2021+ Gas Gas/KTM.

[Moto7man]

Originally Posted by Jacob 'Berg

Double check you did not purchase a head for the 2021+ Gas Gas/KTM.

Yeah, thats a good idea. Lately, I have seen a lot of stuff that is listed/labeled incorrectly.

[Zman]

Is it plain wrong or just tight? It is possible the cylinder is now a little tight and the head is a little big. Can you freeze the head and install it?

[Dario]

Originally Posted by Anders

I have no experience with the S3 heads, but I see that they have several models. Are you sure you got the correct one for your year?

And secondly, are you sure that your bike is a 300? If you recently bought a secondhand bike, some previous owner might have converted it into a 250

I got the one that fits 00-2017. I?m sure it is a 300 since the W?ssner kolben is for 300cc.

[Dario]

I got the one for 00-2017 Model. It also has the right coolant mount.

[Dario]

Originally Posted by Zman

Is it plain wrong or just tight? It is possible the cylinder is now a little tight and the head is a little big. Can you freeze the head and install it?

It?s just a bit tight. Freezing it might work but I don?t know If I would get it out again. Should just pop on like a normal head should shouldn?t it?

[Neil E.]

Carefully tape over the mating surface on the underside of the head. Use something durable like duct tape. Take a small hand file and file all around the pilot nose on the cylinder head. Use care to keep the file parallel to the pilot nose and use continuous strokes and follow the curvature. If it's a really small amount of interference, this should work OK. You can clean the filings off and test fit the head as you go. You may only need to take it down a thousandth of an inch or so.

If you know someone with a metal lathe, they can chuck on a spark plug to spin the head. Careful dial indicator use and swapping around as they tighten the chuck should get it running perfectly true. Then it's just a matter of a very small cut (or it could filed down while in the lathe).

I'd go with the first method as it's easier to check the fit as you go. The cylinder can be off center by a couple of thou and have no detrimantal effect on the engine. The only really important thing is to keep the mating surface of the head (and the oring grooves) in good shape.

[(F5)]

I'd go lathe for square cut in corner then just test with barrel in situ.