I'd like to pick your brains if you don't mind, as I find that I have to remove the cylinder head and eventually the barrel to get to the piston rings as the rings are leaking oil, which is blowing out from the bottom of the engine, but that's another story...
What I would like to know (because I've never had the head off this bike before) what I'm likely to encounter? Is it just a case of heating up the heads of the bolts on the top, removing them and the cylinder head comes adrift? Do I need to then change the head gasket (the copper one?) From here, can I see the number on the top of the piston?or would I need to get the barrel off as well?
Once i've identified the number on the piston, where then is the best place to get a set of replacement rings? Equally, if I need to replace the head gasket, where's the best place to get one?
Sorry for the questions guys, but this is the first time I've ever tried to open up this particular engine, and I really don't know what to expect :-/
Ian unless you have serious corrosion to your head bolt threads, you shouldn't need to heat anything, just undo the bolts (move head steady out the way) and lift off head and gasket. If you clean the carbon off the top of the piston you should be able to read if it's a standard or O/S piston.
But since you need to remove the barrel anyway to attend to rings/piston, I would not pre-empt the situation until the barrel has been inspected and measured for wear by an engineer. There's no point fitting new rings in a worn out bore.....It might require a rebore and new O/S piston.
There is information in the technical section on tightening the head bolts.
Put 'TT John' in the search box, he sells perfect solid copper head gaskets. (See my post in the "engine noise again" thread)
In the Technical Section there is quite a good original workshop manual which is worth printing out. Being a side valve, taking the head off is just a matter of taking the tank off, undoing the headbolts and giving the head a tap with a rubber mallet.
However, if your compression is good and the bike isn't burning oil (haze of blue smoke out of the exhaust), then I wouldn't immediately suspect worn rings.
Oil being forced out of crankcases is usually caused by a build up of pressure in the crankcase, so I would check the breather.
It may be that your bike is merely wet sumping and the breather is slightly blocked with emulsified oil. This means oil in the sump is trying to find its way out wherever it can until such time as the pump has scavenged sump oil back to the oil tank.
Ron,
Thank you for the kind reply.
I actually never gave a moments thought to the cylinder head stay! ;-)
Good point of checking the bore for wear, I shall bear that in mind as well.
Ian
I am led to believe the cause is the oil scraper ring being at fault due to the amount of oil that's blowing out of the breather tube, plus the oil also blowing out from the valve lifter position, both pointing towards a build up of pressure in the bottom end.
The bike does not appear to be wet sumping (I also fitted a valve to prevent this) and the oil seems to be travelling up the return pipe to the tank as soon as the engine is fired up.
No blue or white smoke kicking out the exhaust either.
I have no knowledge on the service history of this machine, so, it is highly possible that something is going to be worn out... It is my sincere hope that it is ONLY a worn ring and nothing else.
Thanks for the heads up though, much appreciated :-)
Ian
