NC24 1987 BAD RATTLING FROM REAR CYLINDER HEAD

[pagan1001]

Alright guys here again to see if anyone can solve a problem!?!?. It started with my fuel tap diaphragm going of old age and the bike coming to a complete stop cause of fuel starvation. I should say before this the bike has been great but that happened and I have just bypassed the tap to allow fuel into the carbs so make sure the tap is turned off when the engine is and on when I go. Anyway now I got it going the rear cylinder head sounds terrible a really bad rattling kind of noise thats the best I can describe it I had been out to check it all when the oil light flashed on, off, on, off then on so I killed the power and the fuel and going to wait till tomorrow to open her up but any ideas will be most welcome guys cheers.

[Old Painless]

If your thinking of taking the head off or something you could try a compression test first and check the oil level.
It could be that the lack of petrol caused lean running which killed the rings and let the cylinder pass a load of oil above the piston. Its a bit unlikely though ?

[MexicanGringo]

Dont run it at all if the oil pressure lights telling you theres no oil pressure and theres a rattling noise! How long did you ride before noticing the light, do you think?

As suggested the problem is probably below the head, so valves, piston, connecting rod or a bearing relating to it. Take the valve cover off and check for obvious damage, drain the oil and look for bits of metal, then you'l prob have to take the rear head off, easier than the front at least and can be done with engine in frame.

[pagan1001]

I noticed the light straight away as was looking for everything so as soon as it came on I switched the bike off so no problem there........... I hope. That sounds possible I am going to start work on it now. I let the bike sit when I got home and went back switched her on again and no light but still noise so it has to be some thing like that. Or can petrol get into the head?????? anyway the front was rebuilt (cylinder head) so the back gasket could have failed or I thought something being in the engine its self blocking the oil passage making its way around the engine as have found fibre like material in the rear one before and the sump strainer which was covered in the stuff. I was told this was from the clutch going with a previous owner and them not cleaning her out. But I dont know!!!??? My first port of call is to remove the rear valve cover and check everything if I find something GREAT! if not then I will remove the parts as the noise sounds loudest at the top cam shaft the inlet. Infact only comes from the top. But I am just guessing until I look in. If everything looks fine and dandy then may check the sump again as well, as something has to be blocking something some where for the light to come on. Like I said before it was running great before the no fuel. But like you said the best way is a compression test but I aint driving her that far to get one and I dont have the gauges so will have to make do just now. But if you think of anything then let me know as any info is highly reguarded cheers guys.

[CMSMJ1]

I'd drain the oil, clean the strainer etc.

If you had fibre in it beore it is not much fo a leap to think something has blocked the oilways and starved the bearings = knackered bottom end and rumbly moto..

[pagan1001]

Okay lads just stripped it down have got the rear head off. It was a killer the front was twice as easy!!! honest. Anyway the inlet camshaft was snapped in half and the two rocker arms on the left were snapped!!!. Who ever has done work on my baby in the past has not got the torque settings and done it by feel or with the new vfr settings which are different cause when I did the front the bolts were never as tight as that and the cam ones on that side were nearly not moving!!! This is what I think but if anyone thinks different then please let me know!!! The rest of her looks good though fingers crossed I have been a lucky bastard!!!. I will remove the sump and spray clean the engine out in case off loose metal then put her together again and see. But this has been going to happen for a while as I have noticed the odd noise now and again but I just got the bike in March and hardly been on her as been doing all the body work. So this may have been the cause off all the problems or let me know if you think there could still be an under laying problem????. I have been lucky as got a whole new head on the bay for £40 including postage the question is do I use the head thats coming or clean up the one that was on her and reuse it????? But cant get the NC24 head gasket again so am using the NC30. Any info would help guys so type away cheers xxx

[Neosophist]

You snapped the camshaft?

Somethings not right there.

You really need to check the oil strainer, see if anythigns blocking it up.

Only way to do this though is to get the engnine out the bike as you'll need to take the sump off to see it (which involves removing the collectorbox / rear downpies (hence the engine out))

If your going to this much trouble I recommend taking the genny case and clutch case off along with the sump and getting hold of a parafin gun and compressor and blasting out the engine with a gallon of parafin (I did mine over christmas but that was due to it being full of water!)

This will remove any metal particles that have gotten in the engine.

Last thing you want to do is cut corners and have the same thing happen again.

Now you see why there such a pain to work on compared to the NC30

You've probably have a blocked oilway causing oil starvation.. id' check the strainer though as that being blocked up will cause your oil light to come on.

[MexicanGringo]

If the camshaft holders are unevenly tightened, or overtightened the camshaft may not run straight, but id expect the holders to break and the bearing surfaces to foul before the camshaft snaps!

make sure the 30 gasket has all the same coolant holes etc, not sure if theyr interchangeable..
Use the new head, but measure across its surface with a straight steel rule, going straight and diagonal, the clearance under it at any point shouldnt exceed 0.1mm.. And obv use the valves that come with it

[pagan1001]

I have done the sump but can do it without taking the engine out. The strainer was fine and it was new oil so nothing in it at all I think some dick has repaired the camshaft at some point!!!!!!! You can see material on it, why would they have done that??? also found a mark that was caused by an angle grinder on the cylinder head frame mount bolt like they just tried to cut through it??? idiots!!!!!. Someone, some time did not have a clue. Have got the side casing off too and have cleaned the inside out. Everything else seems fine but I am still looking into possible causes for the cam breaking just to be safe but am fairly sure its been worked on but it broke just to the left of the central gear cog which makes it a weird break as its bound to be strong there unless someone dropped it or something. Who knows I can only go through the problems one at a time until its all nailed down. Looking up into the engine there are no signs of damage. At this point with the bolts being as tight as they were I am taking it as being that I will clean her out again then put it all back together, if there is any sign of anything then I will strip the engine out and maybe just replace it as will be cheaper and save a hell of my time. But please guys any more info get typing as need to think of all causes to this cheers for all your responses x

[pagan1001]

As you said Mexican Gringo the cam holders should have broke. Just back from a mates house had to take him the bits over he is an engineer and reckons it should never have broke there some other part should fail before the camshaft. Also said work may have been done on it before and not a good job. And that I was lucky nothing major happened cause of it. So I can live with that. Will get parts on thursday so will let you know how she starts......... if she does!!!..... just kidding of course she will they are solid bikes no worries cheers for the input guys x