Shimming the valves
|7000 miles later|
|Central bolts are awkward|
|Oil had collected around the plugs|
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 springsIt 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 CamshaftsWhilst 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|
|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|
|Green cam (left) out and blue cam (right) in place|
|Manual says seal the ends|
|Plenty of Hylomar around the plug recesses|
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.