My question is about the string exhaust gasket that fits in the front chrome outlet a the cylinder head which the front end of the exhaust butts  into....i recently fitted a new one but i am struggling to get a seal has gases can been seen coming out on start up at the front....i assume this is not right?....is there a knack to get this to fit air tight?or can you for instance put gasket sealant there as well....any help appreciated thanks barry ct175.

I'm struggling a wee bit with the same problem on my own CT1, Barry.

On the 250 and 360 bikes it is possible to fit the gasket between the inner and outer ring, but I have found this impossible on the 175.

Make sure that the two exhaust retaining springs are in good order. Also, whilst it is not obvious, the inner and outer ring actually come apart - one is a press fit into the other. I used a wooden mallet and wooden supports to separate and then clean mine. 

I started by bike this pm for the first time after fitting a brand new spring - an improvement, but still a little dribble, so I might apply some sealant.

I've made thin spaghetti-size strings of high temp orange RTV on parchment paper, and used them with excellent results. Let it cure overnight, then stuff it into the flange. It takes patience, but it really works. I just redid it when I repainted the exhaust again. This time I put one thin string in, then seated the exhaust to push it in, then removed the pipe and put another one in.

Here's some I have leftover, and in fact it's better to even be thinner than this.

imgur.com/a/FMNu9Mm