Valve Grinding

[General-Lee 0]

Hey guys, my GN 250 has 4 valves. I've grinded 3 out of 4 successfully, tested for leaks using petrol, none. The 4th and final one, an exhaust valve is proving to be a pain, I've done it 5 times now and it's still leaking.

The valves are new, I can't understand how it can be leaking unless somehow it's just a dodgy one? Any ideas?

Also it struck me today are the valve seats on the head just part of the aluminium casting? Never thought about it before, I would have thought it'd be too soft

[gavlar1200 0]

Hi mate, the valve won't be part of the head it'll be way too soft. We make cylinder heads out of cast iron and still put seats in. Your valve seat may need refacing, when you are lapping the valve and seat, do you have a uniform coating of paste on said valve and seat or are there gaps?

[General-Lee 0]

I see, sounds expensive lol. Uniform coating? I do spread the grinding paste evenly if that's what you mean, the valve and the seat both have a shiny ring, no visible imperfections, no cracks, nothing. But overnight the petrols all over the place :/

[pugeyed 0]

lee have you measured the valve spring compared to the others maybe its on its way out.

[jezza 0]

@General-Lee wrote:

But overnight the petrols all over the place :/

would this not be due to the float valve in the carb.

[dick65 0]

@jezza wrote:

@General-Lee wrote:

But overnight the petrols all over the place :/

would this not be due to the float valve in the carb.

good point jezza my bikes got 20 valves

[Davehutch-hutchs 0]

@dick65 wrote:

@jezza wrote:

@General-Lee wrote:

But overnight the petrols all over the place :/

would this not be due to the float valve in the carb.

good point jezza my bikes got 20 valves

think he is using petrol as a test to see how well they are seated

[jezza 0]

ah just scanned over the thread.