What difference do Triumph green camshafts make?

This post starts off with a simple oil leak and ends up with a cam swap from Triumph green profile to blue profile. It means I now have first-hand knowledge of the performance difference between the two, all else being exactly the same.

Shimming the valves

7000 miles later

The oil leak from the cylinder head cover meant I had to remove and reseal it. I was surprised how dirty the cover had become, after having been so careful in my restoration and with the radiator cowls fitted. But that's because it seems like yesterday when I got Ruby back on the road when in reality a year and about 7000 miles have gone by since then.

Central bolts are awkward

I discovered that the cam retaining bolts were barely more than finger tight. I had torqued most of them down on reassembly. I guess the rubber washers under the bolts and large rubber gasket had settled. That was why I had a leak anyway. I was also reminded of how close the central retaining bolts are to the main frame tube. They are impossible to torque down because even my smallest torque wrench won't fit in the gap.

Oil had collected around the plugs

The leak was not just external. I found puddles of oil around the spark plugs where it had run down into the central wells in the cylinder head. These are all blind to the outside world so there is nowhere for any muck or fluids to go if they end up down there.


As I was dealing with the oil leak from my cylinder head cover, I decided to check my valve clearances. I do not have a special tool for swapping shims with the camshafts in situ, though such tools are available for about 60 pounds. I am happy enough to remove and refit my camshafts when the clearances need to be adjusted.

Two of my exhaust valves were out of specification, needing a change from 2.60 to 2.55. With the cams out, changing the shims is easy - lots of room to move and that in itself justifies the effort for me.

Camchain tensioner springs

It is necessary to remove the cam chain tensioner mechanism to get the cams out. I'd also wanted to replace the tensioner spring. Trevor at Sprint has started supplying replacements. The originals weaken over time and so can't make the internal tensioner ratchet take up the slack in the cam chain as Triumph intended. The picture below shows the difference between Trevor's replacment spring and the old spring I took out. It is photographed over the official factory manual with the minimum spring length.

Comparing old (top) and replacement (bottom) cam chain tensioner springs

Swapping T300 Camshafts

Whilst I was at it (famous last words for me) I decided to swap the original 'green' specification camshafts for the later 'blue' specification camshafts. This was just because I could ... the later motor I had bought had these camshafts in good condition and I wanted to try them out.

Blue cam (left) and green cam (right) side-by-side

The blue cams are far far milder - less lift (shorter lobes) and less duration (pointier lobes) as can clearly be seen in the two side-by-side pictures.

Cam Profile	Blue	Green	Red
Inlet open	1 BTDC	21 BTDC	27 BTDC
Inlet close	30 ABDC	50 ABDC	55 ABDC
Inlet duration	211 degrees	251 degrees	262 degrees
Inlet lift	7.1 mm	8.9 mm	9.4 mm
Exhaust open	28 BBDC	51 BBDC	54 BBDC
Exhaust close	2 ATDC	25 ATDC	28 ATDC
Exhaust duration	210 degrees	256 degrees	262 degrees
Exhaust lift	7.0 mm	8.6 mm	9.3 mm

The table above shows cam timing in degrees relative to the extremities of the piston stroke: before top dead centre (BTDC), after top dead centre (ATDC), before bottom dead centre (BBDC) and after bottom dead centre (ABDC). The blue cams have relatively little overlap in period (58 degrees compared to 101 degrees for the green profile) meaning that the exhaust valves close early enough to maximise effect of the charge. The green cams overlap considerably.

Green cam (left) out and blue cam (right) in place

Manual says seal the ends

Plenty of Hylomar around the plug recesses

Finally, I was very careful to seal the cam cover with Hylomar, following the factory instructions. I was confident that this would work because the rubber gaskets have now thoroughly settled and I was more generous with the Hylomar (but still VERY careful) than last time.

So, what difference do blue camshafts make?

I have ridden about 500 miles since installing the blue cams. What difference do they make? A lot. Performance (better below 60mph, worse above) and fuel economy (between 5 and 10% better) have changed.

The engine now pulls solidly from 2000rpm. It is both stronger and linear, whereas previously it would pull but with some hesitation, especially around 2500rpm. The low-rev thrust is a transformation. That is a brilliant improvement. However, the cost as I suspected is that the old kicks at 4000rpm and at 6000rpm have gone. I am not surprised by this after having read contemporary road tests of the original and re-tuned Trophy 1200s.

I can live without the 4000rpm step because it was probably just a sign that cylinder fuelling wasn't working super well below that engine speed. However, the way the engine came on cam at 6000rpm was exhilarating and I miss it. Realistically, I might experience that once or twice on an average ride because the roads around here are not suited to high-rpm riding. But experience cannot be distilled into numbers like 'twice per ride'. I shall be reinstalling the green cams in the next few weeks when I swap the engine covers over for powder coating.

On the other hand, the blue cams make for a much more relaxing and secure riding experience so I have decided to use them in late Autumn and Winter when I think they would suit riding conditions perfectly.

Consequence: I now have two engine tunes available, one for summer and one for winter. Very nice.