As we all know the airhead engine is a superb, robust engine. One of the problem areas on higher mileage engines is the valves. I'm just in the process of refurbing my 78 R100 engine, there are a few minor differences between these heads and the later GS engines but essentially they can be regarded as being the same when it comes to working on them and cleaning them up.
This is a high mileage engine thats started to feel a little breathless, it still runs well but has been lacking a bit of zip and not ticking over as well as it should.
It's a very easy task to pull the heads off - this is what you are left with. A pretty grubby lump of metal with 30 years of grime encrusted into it.
The carbon build up is obvious. Multiple layers have built up on the valves and the combustion chamber.
You need a valve spring compressor to release the collets and remove the springs, once these are out everything becomes clear - There is so much carbon on the exhaust valve and in the exhaust port that the valve is not shutting fully.
The exhaust valves in poor shape. The contact point between the valve and the valve seat is burnt and pitted.
This picture shows the contrast between the inlet and exhaust ports. The inlets obviously on the left and is in surprisingly good condition compared to the exhaust.
The head of the exhaust valves can snap off, taking out the cylinder head, barrels and pistons. The recommended interval between valve overhauls is 40 - 50k. The valve heads are welded on, when you see how the carbon builds up it's easy to imagine the stress placed on the valve.
The valve guides on this engine have play in them and need replacing. Replacing valve guides needs specialist kit so I'm shipping mine off to SEP for the work to be done. Before they go off I need to know if the valve seats are serviceable. Fit the new valves and give them a gentle grind using a grinding stick and paste (£3 from halfords) - These seats are fine.
I'm lucky because I have access to a bead blaster at work, a few minutes at lunchtime does wonders for the cylinder heads.
Once the guides have been fitted The heads can go back together - shouldn't have to worry about it again for another 50k
Motobins supplied the complete valve replacement kit. 4 genuine valves, 4 new springs, collets and 4 valve guides for £81. Having the guides fitted is going to be in the region of £60.
This is a high mileage engine thats started to feel a little breathless, it still runs well but has been lacking a bit of zip and not ticking over as well as it should.
It's a very easy task to pull the heads off - this is what you are left with. A pretty grubby lump of metal with 30 years of grime encrusted into it.
The carbon build up is obvious. Multiple layers have built up on the valves and the combustion chamber.
You need a valve spring compressor to release the collets and remove the springs, once these are out everything becomes clear - There is so much carbon on the exhaust valve and in the exhaust port that the valve is not shutting fully.
The exhaust valves in poor shape. The contact point between the valve and the valve seat is burnt and pitted.
This picture shows the contrast between the inlet and exhaust ports. The inlets obviously on the left and is in surprisingly good condition compared to the exhaust.
The head of the exhaust valves can snap off, taking out the cylinder head, barrels and pistons. The recommended interval between valve overhauls is 40 - 50k. The valve heads are welded on, when you see how the carbon builds up it's easy to imagine the stress placed on the valve.
The valve guides on this engine have play in them and need replacing. Replacing valve guides needs specialist kit so I'm shipping mine off to SEP for the work to be done. Before they go off I need to know if the valve seats are serviceable. Fit the new valves and give them a gentle grind using a grinding stick and paste (£3 from halfords) - These seats are fine.
I'm lucky because I have access to a bead blaster at work, a few minutes at lunchtime does wonders for the cylinder heads.
Once the guides have been fitted The heads can go back together - shouldn't have to worry about it again for another 50k
Motobins supplied the complete valve replacement kit. 4 genuine valves, 4 new springs, collets and 4 valve guides for £81. Having the guides fitted is going to be in the region of £60.
