Leaking decompression valve

The decompression valve on my Piaggio Si leaks, resulting in terrible acceleration, low topspeed and a whining sound from the cylinder. How do i take it apart so i can properly clean it? And should i buy some kind of sealant? Or should i just buy a new one?

I was an incredible idiot and opened the valve while i was going topspeed because someone told me it'd make loud explosions, which i of course wanted to try out.

Re: Leaking decompression valve

You may have burnt the valve .

Remove the head and inspect .

Report back .

Re: Leaking decompression valve

Dirty30 Dillon /

Disassembly is easy. You will need to clean and reseat the valve to return it to normal. Also check your topend for smearing, as opening the decompression at speed can be pretty traumatic for the motor

Re: Leaking decompression valve

Yeah you can lean it out and destroy the top end doing that.

You probably just got some carbon in the valve...take the head off, dis connect the decomp cable and have a look. Probably just need some lapping compound to reseat the valve.

Re: Leaking decompression valve

Well yes i had it open and tried cleaning it, and it's gotten better, but it's still leaking. However i don't have any lapping compound, apart for some thin band made for wrapping around stuff. Is it possible to do without lapping it? And how do i get the valve out?

Re: Leaking decompression valve

Correction: I know how to take the cylinder head off, i'm asking how to take the decompression valve out.

Re: Leaking decompression valve

Dirty30 Dillon /

> Sølver Bue Wrote:

> -------------------------------------------------------

> Correction: I know how to take the cylinder head off, i'm asking how to

> take the decompression valve out.

Remove the cotter pin, and it will come apart. It's not difficult.

You need lapping compound, there's no reason to work a round a small expense to fix it

Re: Leaking decompression valve

The liquid compound, or some type of gasket? A friend of mine says the liquid stuff is a last resort, and the gasket will last you forever.

Re: Leaking decompression valve

> Sølver Bue Wrote:

> -------------------------------------------------------

> The liquid compound, or some type of gasket? A friend of mine says the

> liquid stuff is a last resort, and the gasket will last you forever.

Friends ... they mean well , some times . But , sometimes , they don't know what they are talking about .

Stop by the auto parts store and pick up medium lapping compound .

Check out a YouTube video for how to use it and fix your bike .

Then you can let your friend know exactly what really works . ;)

Re: Leaking decompression valve

u can use car rubbing compound, or hand cleaner that has the pumice as well or anything that has some fine grit.

Re: Leaking decompression valve

Also, is the plastic piece on top of the cylinder that moves the air from the plastic piece on the fan from one side to the other really necessary? I understand not having it can cause irregular heating, but does it even matter in the first place? Aren't the cooling fins enough?

Re: Leaking decompression valve

Dirty30 Dillon /

> Sølver Bue Wrote:

> -------------------------------------------------------

> Also, is the plastic piece on top of the cylinder that moves the air

> from the plastic piece on the fan from one side to the other really

> necessary? I understand not having it can cause irregular heating, but

> does it even matter in the first place? Aren't the cooling fins enough?

You need the plastic piece. Tried running without myself, and it's not good.

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