Assesing if valves and cams are ok?

[kikdbak]

Ok I got the engine apart with some helpful info ..thanks guy.

The rings were paper thin..no joke.

the valves have alotta carbon on em ...and i have started to clean it off.

But i am not sure how to assess if the valves are ok?

And if the cam is ok? no obvious signs of wear but I can't seem to makes the valves open
i am woundering if they are siezed but it was running yesterday or do they just take aloota pressue to open.

 

[sean01]

the valves take a bit of pressure to open due to the valve springs.

best thing to do to see if they are sealing is to make sure the valves are fully closed and fill each port up with fuel or kero and see if the valves leak in the chamber..
if the they leak then they may have some crap under them if there's no crap then they need attention..

also to get the valves fully closed your going to need to get the cam on top dead center and make sure the valve clearance isn't holding them open..

 

[rumble]

Its good to see your a noob at engines but given it a crack!!!

Why did you take it apart for in the first place?

You wont be able to push the valves open by hand. One way to check the valves are sealing, which normally indicates they are not bent, is to pour, i like metho, down intake and exhaust ports. What your looking for is any leaking into the area where you see the carbon build-up. This is where you pour the metho or kero or petrol ect

If it leaks, something is wrong!

As for the rings, have you seen new rings before?? some are thin.

Another thing to look for is the bore where the piston runs up and down. You should be able to see light scratch marks zig zaging the bore. None going up and down.....

 

[kikdbak]

Cheers guys. I will do the kero thing.

So i am gathering as long as they seal they are fine. And that is why it helps to remove all carbon etc..

I havent seen new rings except on 2st dirt bikes... but 2 of these were like hairs and one fell apart when i touch the piston..the oil one

I took it apart because it had bugger all pull in the motor.. an was blowin piles of smoke out the exhaust and breather..

And I wanted to see if I could....having great fun.. will buy another after this an hot it up..this baby is stayin stock coz my daughter rides it also.(haha she thinks it hers)

It is something i love learing about...

 

[kikdbak]

Thanks .. I checked valves sealing as above method. and they seal .. so I have just cleaned up carbon on surface. And I gather they will be fine.

Putting this back together valves etc at top dead centre, it gonna be interesting..

i have done 2st. never a 4.

Not as scary as I thought. And I have fallen in love wit the little haonda all over agian in the process.

No real cross hatching in the bore...maybe a slight bit at the bottom ... It is a bit dark it one bit.. but i got a bike mechanic to look at it he rekons its fine.

He measure it an it was in spec 47 mm....

Got me thinking.. what purpose does the cross hatching serve?

 

[sean01]

honing the cylinder removes any imperfections in the bore.. hot spots, high spots, lip at the top of the bore and so on..it also makes sure it is square and not tapered which is common for a secondhand bore.

the cross hatching is for oil retention which helps lube the piston and cylinder and reduce the amount oil consumption..
a freshly built engine with no cross hatching will more than likely use oil again and ring bed in will suffer.

while most people just simply hone and replace the piston and rings theres more that should really be looked at, specially when using non genuine parts.

most of the time you will just get away with replacing and not measuring but engine life will be reduced if it is not in spec..

piston sizes from one manufacturer to the other will have a different out side diameters so you need to measure the piston to bore clearance..

also you need to check the ring gap to be sure the cylinder isnt outside of its service life.. you need to check in 3 locations.. top of the bore middle of the stroke and bottom of the stroke...
of course a new ring would be needed to check the ring gap.

i could go right into it but i think iv aid enough already lol..
actually do a site search here and youll find a thread purely on honing..

you say you had the bore checked out, what method was used to do this.?

 

[kikdbak]

Hmm it certainly didn't seem that intensive.

He measured top and bottom of bore with calipers...

 

[sean01]

calipers cant measure bore clearance..
you need an inside micrometer and an outside micrometer..