philhill Posted November 13, 2013 Share Posted November 13, 2013 Hi, have not been on here for a while but still have my DT, nearly sold it recently though as was getting fed up with holing pistons!! Have gone up to 220 on the main jet but still holed a piston after overtaking a car at full revs. Now rebuilt but have gone back down to a 195 main as it was running rough and was better with this jet though still not right. Was passing a motor factors the other day and thought I would drop in and get a new spark plug as guessed that might be the problem. They didn't have a E8ES only a E6ES which the bloke said was cooler but should work only it might not last. After putting it in it now starts with just a half hearted push on the kick start and goes like stink!!! I still haven't done a prolonged thrash to see if it will hole the piston again for obvious reasons but as its running so well am tempted to give it a go down the bypass. Before I do I thought I would just check with you lot to see if this is wise as another piston hole will force me to sell and I don't really want to as its great for blasting around town and getting to work and back. It's also been a great winter bike and can get me to work when the car can't. But I do want it to be reliable for longer journeys and the odd blast. Any comments? 1 Link to comment Share on other sites More sharing options...
Moderator Airhead Posted November 13, 2013 Moderator Share Posted November 13, 2013 Hi Phil long time no see The correct plug is B8ES, cant understand why you are holing pistons so much, your jetting is way over size...160 would be more like it for a mk 2 model or 130 for a mk1 I'd check your ignition timing if I were you Link to comment Share on other sites More sharing options...
philhill Posted November 13, 2013 Author Share Posted November 13, 2013 Hi Airhead, sorry the plug is a B6ES not what I wrote. If I remember right the timing is not adjustable and as i said it starts very easily now with first or second kick and full choke from cold so think the timing must be ok? I started with mains around 160 but have kept going up with each holed piston!! Thinking about it I was on the 195 when it last holed but went up to 220 then back down after replacing the piston. It's running really well on the 195 now, it's over bored to +1.50 and has a K&N type filter, exhaust is repaired standard if that helps to explain?? Link to comment Share on other sites More sharing options...
philhill Posted November 13, 2013 Author Share Posted November 13, 2013 I have read in one of the manuals for this model that an earlier model than mine was supplied by the factory with too hotter plug causing overheating problems and it was replaced with the B8ES ( I think, from memory ). With this in mind is it possible that using a cooler plug will reduce the running temp and help avoid a piston holing? Also does modern petrol burn hotter than the old leaded stuff? Link to comment Share on other sites More sharing options...
philhill Posted November 13, 2013 Author Share Posted November 13, 2013 By the way it's a later model from 1982. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted November 13, 2013 Moderator Share Posted November 13, 2013 bloke told you wrong, I run a B9ES which is a colder plug than the standard B8ES http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp Link to comment Share on other sites More sharing options...
philhill Posted November 14, 2013 Author Share Posted November 14, 2013 Oh right better get that spark plug changed for the right one or your cooler one before any damage done. Good job I checked with you! Will study that web site later. Thanks! Link to comment Share on other sites More sharing options...
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