serious engine issue

[leef82]

well after a full engine rebuild and starting it the other week for the first time in two years i was quite happy with how it was running apart from a bit of backfire at high revs which i wasnt overly worried about,
untill today i fired her up and left it running for 20mins everything normal, switched it off then decided to fit a rick o earth kit, anyway got that done fired it back up and 20secs later a rattling appeared tot end front, not sure if iwas immagining it i gave a few more revs until it stoped then it woudnt start unless i used the throttle, then the rattling got bad so switched it off took the carbs rad off etc , took the front cam cover off to find this


shock shock horror , the pin that goes through the cam arms has come out and hit the cassette teeth,ive lost the shim and the little cover that sits on top of the spring, idont know if the spring has come loose or what?

[Neosophist]

You havn't reassembled the engine properly

The 'pins' (bar thats come loose) that hold the rocker arms in have a half moon cut out in them, they have to be locked in place by the 4 corner bolts of the cam-cap holders (the cam cap holder corner bolts are slightly longer than this to allow you to lock them in place)

Either the smaller bolt from the middle was used, or most likely it wasn't pushed in properley and aligned (use a 6mm bolt and twist the pin to align the cut-out with the bolt) when the cam-caps were installed. So it's worked loose.

You can see from the second picture the 'half-moon' cutout in the pin, that should be held by the bolt.

Oh dear! Unless i'm mistaked, what I can see from the first picture.

The valve has dropped out! You've lost the collets that hold the valve, the valve retainer and the shim (the shim IS the small thing you mean that sits on top)

The nosie was probably the valve hitting the piston and the cylinder

It sounds like the engine might be destroyed beyond repair now. you'll have to take the cylinder head off to see the damage to the piston and cylinder, damage to the cylinder usually writes the engine off as the cylinders are not removable from the engine cases.

You'll need to find the valve collets and shim and retainer, they are probably in the sump if not floating around the top end but it looks very bad i'm afraid.



Not an NC30 valve but you can see the lableling. Your valve spring retainer (metal cap) and collets (labelled 'lock valve spring retainer') have come off becuase the shim and rocker arm moved and the cam pressed it down.

This caused the vavle to drop out into the cylinder and cause much damage



This is an actual shim. they sit ontop of the valve and stop the collets (valve lock) from coming out when pressed down, as your rocker arms have moved the shim has come off, the valve has got pressed down without this inplace, this causes the valve retaining collets to come out also, the valve fall into the engine and damage / noise.

[leef82]

that makes sense, i was thinking that may i hadnt put the collets back in properly as i remember them being fiderly, also i was thinking that the valve had jammed it self up clear of the piston , well fingers crossed , ill be gutted if it a gonner as i spent a lot of time and money on that engine, oh well as soon as i get a day free i shall have a proper look,

[force-v4]

The actual, exact same thing happened to my mate @ the start of the year, he was very lucky & got away with just replacing a valve, cam & rocker arm. Nothing made its way into the engine - good luck.

[Neosophist]

that makes sense, i was thinking that may i hadnt put the collets back in properly as i remember them being fiderly, also i was thinking that the valve had jammed it self up clear of the piston , well fingers crossed , ill be gutted if it a gonner as i spent a lot of time and money on that engine, oh well as soon as i get a day free i shall have a proper look,

Valve will most likely have hit the piston, hence the knocking noise.

You can test the collects by putting the shim on and pushing the valve open a few times, this will make sure the collets are seated right. I believe it's becuase the rocker-arm moved, the shim dropped off and this allowed the collets to come out.

If it's broken it could have cause much damage, only way you'll know is by taking the head off.

when you reassamble if it isn't beyond repair.

The 4 corner bolts of the cam covers are longer than the inner bolts, make sure you push the rock arm retaining pin / rod (the thing that came loose) full in and rotate it until you see the half moon shape cut out align with the hole, use a bolt to check it's in right and then reassemble.

Get some pictures up when it's done.

[leef82]

seems i was a wee bit lucky, i took the cams off and found the collets and the bit the shim sits in, it appears the valve stayed up and is moving freely up and down so it doesnt appear to be bent or damaged so i didnt take the head off, the only damage was a groove ontop of the rocker arm and bottom of the cam whitch i smoothed over with wet and dry, the bolt that holds the rocker pin was the correct one as it has that thicker shaft above the thread so all i can assume is that we didnt notice the pin was slightly sticking out the end, as for the noise i think it was the pin hitting the wheel as it was jammed against it, so i refitted the collets spring etc using a adapter from the valve spring compressor and a g clamp hooked under the exhaust, cams refiited the only thing is we didnt find the shim in the sump and could not find it with the tele-magnet , so im going to borrow a shim from else where and work out what size i need,

[james....]

You really need to think about where that missing shim could end up....blocking an oil gallery on even could it find its way into the cam drive or gearbox!

[lukemillar]

Yep, I'd be tracking that badboy down before even thinking about starting the engine again!

[Neosophist]

Hmm

Have you taken the sump off? It might be in the strainer.

If not theres a raised platform by the gearbox, most likely there.

I had one fall down into the rear cylinder head and was jamming in the gears or camdrive or something, couldn't rotate the engine and the shim had teeth-marks in it when I eventually got it out.

[leef82]

yeah ive checked the strainer, ive stuck the telescopic magnet down between the cams till it comes out where the sump is, ran my hand up inside as far as i could trying to feel it but no luck, the bike proberly aint goingf to be on the road till next year, so all i can do is run the engine once a week and hope the flow of oil moves it to the sump, i dont like the thought of splitting the cases just to get a shim out, fingers crossed