Is this a BURNT valve ?

[themadatter]

Hello !!


I took my head off and got the valves out.

None of them where stuck.

Both of them where black some bit up the stalk.

The valve I think may have been burned is the inlet valve, becasue the bike pops through the carb instead of starting.

The only difference i can make out is that if i push the inlet valve closed, it makes like a pumfff sound like its sealed off airtight.

When i close the iexhaut valve it makes a, metal hitting metal sound.
not the nice sound of the inlet.

anyway,, help would be appreciated, I need to order parts tomorrow !

strange cuz i thought it should have been other way round ...
If this sounds burnt, then what should I do ?


thanks
Jamie

[Guest]

It'd be very unusual to burn an inlet valve but you should be able to tell by looking at it ........

https://www.newmonaco.fsnet.co.uk/images/head.jpg

Has the inlet valve got an oil seal at the top of the valve guide? That would make it harder to push in than the exhaust valve and probably produce to noise you describe, though they're usually fitted to all the valves as far as I know.

[Kickstart]

Hi

Some engines are designed with an oil seal on the inlets but not the exhaust.

I would expect the non burnt valve to go in with a metallic click. Basically a burnt valve will have serious pitting where it seals against the valve seat.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[themadatter]

Thanks guys,,


valves are not burned then...


it is a timing problem.

i didnt line up the tdc marks when doing the timing so maybe when i readjusted the valve timing, it was off.

thanks !

Jamie

[MalcolmT]

Quick test I use to check the seal is to assemble the valves and pour petrol into the ports one at a time.

The fuel will soon creep past a leaky valve an show up in the valve.

[Big Pete]

DO NOT USE PETROL!!

use diesel or parrafin, apart from the fire risk of having raw petrol splashing around, its very hard on your skin (dermatitis anyone?). Parrafin is ideal as it hass good creep properties and will find its way past badly sealed valves. If you have got the timing out, the valve stem could be bent.
____________________
Trust me, I`m an engineer
GarageOfPower.co.uk