I've just acquired a 240, which appears to need new crankcase seals. I'm a bit daunted at the prospect, without heading off to Yorkshire, does anyone know a suitable workshop in the South East who may be able to help?

You sure you need seals ? Does it run very weak / erratic, dry side seal. Burns gear oil which generally looks different to 2stroke smoke ? Other side.

Not just the exhaust needing a good clean out ?

I’ve cleaned out the silencer and exhaust with caustic soda. It was running with an oily gunk. This seemed to clear the smoke a little, but not eliminate it. The bike was running fine at this time. As the smoke began to return the bike started to run “flat”. The bike had stood for a while so, I hoped it would clear, but it hasn’t. 

Its running on 50-1 on a Putoline Synthetic oil.

Seals can easily be changed from "outside" - any competent mechanic should be able to do the job for you in short order, if they obtain rhe right puller.

To change crank seals on a 240 I'm afraid you will need to separate the crankcase unlike the later engines, presuming it doesn't have a later engine fitted? 

I've attached a Tec sheet with some useful information in case you don't have it. 

Fantic 240 OM.PDF

My apologies, it seems that model has the seal inboard of the main bearing on the drive and that's the side that could be causing your problem.  But you'd do both anyway.  Still simple enough for a competent mechanic.

Edited February 5, 20197 yr by 2stroke4stroke

Thanks all for the info. Its been suggested it could have a build up around a restrictor on the front pipe? I'll try to decoke it again, any suggestions other than Caustic Soda. Does anyone have any suggestions on a replacement exhaust system or who may be able to remove the restrictor, I'm in Essex. Many thanks

I clean my 240 exhaust by burning it out, I have used a blow torch in the past but it takes ages, now I build a fire and put the exhaust on top - get it really hot and wait for the smoke to stop coming out, you will know when it is clean.

You will get a hundred opinions on the amount of oil to use, but I am happy running my 240 at 66:1 using fully synthetic trials specific oil, usually Putoline.

Have you changed the gear oil? If the LH seal is leaking you should get noticeably less back out when you drain it after doing a trial. I have noticed mine running 'flat' as you describe it when it has been burning its gear oil, different smell to the exhaust too.