Part 6 - The Carburetor

After the success of a easy engine start the bike went for it's 'daytime' MOT and passed with flying colours. However, the subsequent extended ride home left me somewhat disappointed. The carburetor was clearly not working too well.

The carburetor had pretty much been ignored during the rebuild. It was clearly time to re-furbish it.

I purchased one of the Keyster kits available here in the UK and proceeded to dismantle, clean and resemble. I don't have ultrasonic cleaning facilities so some very small nylon bristles were used. The Keyster kits include all jets and float valve etc. and once fitted leave the carb looking very tidy. However, during the rebuild I noticed that the needle ring fitted to these machines, was missing from the top of the needle.

The Kitchen Worktop Makes a Great Bench

This is something of a 'gotcha' as many of the models don't have this and can easily be missed when following a service manual. However, it can make a big difference to the running. During the search for this elusive part I discovered that there are many different throttle sliders, some that use a needle ring, some that use a 1mm washer and others that don't use a ring or washer at all. This makes things very confusing.  

Missing Needle Ring

In the end I managed to source the item here in the UK (Martin Crook). On this particular model of Carburettor the needle ring fits on top of the needle with the spring below. When this is assembled the ring is responsible for lowering the needle into the needle jet by exactly 2.5 mm (99 thou) from the circlip.

One interesting, albeit, confusing thing is that the plate that fits on top (15) to locate everything as two small pressings which protrude, one from each side. This prevents the needle ring (17) sitting flat against the plate. This causes the needle to be sprung to one side slightly. I assume there is a good reason for this. However, this does seem rather odd and it makes it tricky to locate the slider without fiddling with the needle through the air intake of the carburettor.

After many hours of discussions on the Suzuki TS forum, suggests that either the plate may be the incorrect item, or that the needle ring should not be present. As each parts book and service manual shows the needle ring in place. I decided to simply re-engineer the plate and remove the 'bump' and reassembled the carburettor. After the first test run, it was clear that the ring should be in place and the slight modification to the plate was the correct course of action. Needless to say that there are many confused TS250 owners still struggling to understand what the bumps are for, me included.

I guess time will tell if everything is in order and that the mixture is correct across the operating range. I suspect the some small adjustments may be required as I use the Bike more. Either way I am happy for now as it runs well and starts easily.