NC21 Stuck Exhaust Valve

[harty210]

The bike hasn't been used for about 15 years and unfortunately I think the fuel tap was left on last time it was started, don't know if this was sooner than the last 15 years, and the carb on no.3 cylinder has leaked fuel onto the back of the valves which has sat and gummed the back of the valve, when turning the engine over by hand the valves have stuck open, due to the fuel glazing I think, I am currently trying some degreaser on the back of the valves to see if it will help if I can clean them up without removing the head.








If this doesnt work and I do have to remove the head, does the gear drive to the cams make this a harder job than on an engine with a chain drive for example, and is the timing procedure the same as in the NC30 Workshop manual? If not would someone have a timing procedure please?

[richyrd5]

Its the same as any gear drive honda.i would DEFINNATLY take the heads of there mate.as u dont wat is lurking.least u know its all good then

[harty210]

It is frustrating as the other three cylinders are perfect, I was just dubious as I have not stripped a gear drive head before and wondered if it was fairly straight forward for the rebuild.

[Morespeedvicar]

Can you take rocker cover off, take cam out and tap the top of the valve with hammer and a drift, done it before on a few seized car valves. Take the plugs out aswell and give it a few turns over before you try n start it.

[CMSMJ1]

the gears make it miles easier than a chain - it goes on the right way and is easy to check. none of this tooth out bollocks.

That does look very very very fucked...what are the piston rings going to look like?

[richyrd5]

Thats wat i was thinking cmsmj1.wat is the rest ov it like!get the head of or u will be sorry!!"

[CMSMJ1]

Thats wat i was thinking cmsmj1.wat is the rest ov it like!get the head of or u will be sorry!!"

Do your thoughts rattle about in that random txtspk bollocks as well?

The inside of that motor is txtspk - that valve is bolxd

[Neosophist]

I've seen worse.

It's expensive to replace head-gaskets though, plus if the inside is knackered then its going to write the motor off, I picked up a running NC24 engine for 20 quid + postage.

Its going to cost 3 x that in gaskets alone then any work that needs doing.

This is not a course of advice but it if were me id get that valve cleaned up without taking it apart if at all possible, flush it out with a shit load of parrafin ona parrfin gun and dump the oil / drain sump.

Fill with some fresh cheap oil, high cleaning diseil oil will mop up any crap and run it for a bit hoping it burns everything off, compression test will tell you if its in need of anything more..

if your valve heads are damaged then youll obv have to get it off and re-grind them in, i had this with a zxr that had rusted valveseats but i bought back an nc24 before thats still running now by doing a similar thing.

All depends on how much your willing to pay, how much budget you have and tools / skills you have about.

In a money no limit perfect scenario youd take it all apart, clean everything off, check valve runouts, grind valve seats, check replace bearing shells, valve stem seals, valves etc.

But in the real world after cleanign up the valve and giving it a run it will probably be ok for what its intended purporse is.

[richyrd5]

Thats wat i was thinking cmsmj1.wat is the rest ov it like!get the head of or u will be sorry!!"

Do your thoughts rattle about in that random txtspk bollocks as well?

The inside of that motor is txtspk - that valve is bolxd

Going of topic here but..nothing wrong with txtspk.when ur doing all this from a mob fone!! Just usually cant be arsed writing the full word.plenty of thoughts rattle around mine.but u definatly DONT wanna hear them!!!!beleive m e

[harty210]

Well there are definitely 2 trains of thought on this topic, which is why I raised it in the first place, and I have been torn as to which line to take.

I have to say Neosophist, after seeing a gasket set is £70 or £30 for the head gaskets alone, and although the bike is a project and I dont mind spending a bit of money on it, i would rather not get into unnecessary work, the bike cost me £150 and was supposed to be a fairly straightforward project to clean and powder coat the frame and sort the fairings out for a reasonably low budget, to get a clean tidy looking bike, as I don't have loads of money to throw at it, but at the same time don't want to cut corners.
Therefore I have been thinking along the lines of if I can free it up and degrease it the best I can without removing the head then hopefully any residue should burn off with a bit of running, as it was caused by fuel on the valves and not water. and if that doesn't work then I bite the bullet and strip the engine or worse case replace it. I am looking at the bike for road use so as long as it runs well and has good compression then I am not looking for super track performance.