Wednesday, December 28, 2011

Oil cooler subframes, large and small

The 1991 Triumph Trophy 1200 is fitted with an oil cooler, in common with all other faired models. The first models were all fitted with the same cooler - a 9 inch wide, 5-row aluminium radiator with fittings for banjo bolts. Some time in 1992, the factory started fitting larger versions to the 1200 models - a 10-inch-wide, 7-row radiator. This required a larger cooler subframe.

5-row subframe on the left, 7-row subframe on the right
This post shows pictures of the two cooler subframes next to one another (along with a variety of old engine gaskets pending replacement!). Triumph also changed the oil lines so that the banjo fittings were positioned on top instead of underneath the radiator. I suspect this decision was to protect the fittings from corrosion because muck accumulates on the lower edge.

7-row cooler subframe
5-row cooler subframe

The later subframe has two angled brackets on the top edge, the angles to make room for the top-mounted oil lines.

With the 5-row subframe on top of the 7-row subframe,
the size difference is clear
I want to preserve as many of the fittings of the original bike as possible but think the larger radiator is a good idea. My bike had been running hot when I rode it home. I intend to try fitting a 7-row radiator from a later Sprint 955i into the smaller frame. I've got some ideas on how to do this. 

Thursday, December 1, 2011

Cams and cam chain tensioner

The cams were in beautiful condition - the lobes were factory fresh with a mirror finish. There was a lot of white silicon sealant around the cam box. The manual advises to use it on the two end sections. Cleaning it off was fiddly - I have a single-edged razor blade for the purpose.

The cam chain tensioner is a spring-loaded plunger that bears against a reinforced section of a rubberized blade. The first 1200s had a metal plate fitted to help position the blade against the blade. I imagine there were some problems with this because the manual advises that it should be removed. 

Cam tensioner unit is visible in lower right corner of the blue box.
The problem metal plate is the cadmium plated part that is
visible around the plunger 

I tried refitting it at first to understand what the issue was. It was tough to get it around the blade because the rubber had swollen. 

The end of the camchain tensioner is visible in the center

Carbs and filter

The carbs were in good shape overall - just a bit of muck in the float bowls and the needles were muddled up (the inner two are a pair and the outer two are a pair).

The code for original 1200 carbs is visible on the side: 1240010. 

Other than the swapped needles, the only other problem was corrosion on the float bowl mating surface, visible as white powdery substance, which lead to a fuel seep. 

The airbox had cracked had been taken apart before and badly reassembled. The box-to-carb rubbers had been refitted upside down. This is visible in the picture to the right as an inlet ribbed section at the bottom of the rubbers. These should align with air pressure equalization apertures on the top edge of the CV carbs.  
The box had also failed on the lower edge where the two halves screw together. It is not designed to be disassembled - when the air filter is passed its service limit, the idea is to swap in a whole new air box complete with new filter. However, the fact that is screwed together rather than glued or plastic welded means it is possible to remove and clean, or replace the filter with an aftermarket part. I read somewhere that the original filters were made for Triumph by PiperCross. They are available on eBay.  Lots of people replace them with K&N filters though. 
Airbox disassembled - note ragged side on lower left-hand edge.
This is where the plastic had failed, probably by over tightening.
I chose to clean my filter and to repair the splits by welding them up with a bit of plastic filler rod and a soldering iron. I also drilled holes for a through-bolt either side. I made this up from stainless rod and a couple of stainless domed nuts locked up against regular hex nuts on the inner edge.