Thursday, December 1, 2011

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. 








2 comments:

bostik said...

Never noticed this post before!

That air box was in a poor way wasn't it and I'm intrigued by the varying colours of your float assemblies. What's that all about?

Any sign of wear on the needles?

LeT said...

I only just noticed your reply.

Yes, there are noticeable wear marks on the jet needles just below the five clip slots, where they have rubbed against the slides. I had wondered if this wear might make a difference to the way they run up and down in the needle jets but there is a lot of lateral movement anyway. I guess I'll replace them eventually but so far it isn't interfering with the way the bike is running so I'm not too concerned. I'm getting 44mpg in these early post-rebuild days.