We all know the saying “If it ain’t broke don’t fix it”, well I use my Dommie all the time and don’t do a thing to it. I check the oil and put petrol in it and that’s all. It starts easily and away I go.
Wednesday evenings are “Bikers Nite” ride outs in Gloucestershire and before I went I thought I’d wipe the Norton over and check the oil. The bike never has any in the primary, but every so often I put a bit in as a special treat for the bike. It usually ends up on the floor outside the pub I’ve ridden to, but at least the chain’s been oiled. I lock up the garage and get my jacket and helmet on, go to kick start the bike and the clutch slips and there’s no way I can start it. So I open up the garage again and drain the oil. It still slips, so I have to flush the oil out with a jug of paraffin. I kick and kick until the clutch grabs again and start the bike, then drain out the paraffin. I’ve always used engine oil in the primary, but I notice the Haynes manual for the Dommie, says to use Castrolite, the same as for the forks. I repeat the process with thinner oil, with the same results.
Really I should take the primary case off and tighten the clutch springs but I’m now running late and hot and bothered, as it’s a boiling hot evening. I have no choice but to quickly flush the oil out again and get going. I meet up with my mate and I follow him down the bypass doing 70-80. Suddenly there’s a loud bang..! I feel it through the footrest. I’m thinking is the clutch falling apart or maybe something has jammed in the chain and broken a tooth. Everything sounds sweet for a moment, then another loud bang, It felt like something’s hit my foot. I look down and there’s no obvious damage or any nasty grinding noises. I can’t get off the bypass so I have to keep going. It does it again, it feels like an explosion but the engine’s running fine.
My mate has realised something’s wrong and slowed down. I tell him something’s going bang so I’m taking the Dommie home to get the Harley. I have to go to the end of the bypass, round the roundabout and back down the other side. All this way and the bike’s fine, so decide to stick with it and lets get to the pub. As I go round the roundabout to get back onto the beginning of the bypass again, there’s another loud bang. It didn’t do it again and we rode the 25 miles to the meeting. My mate was behind me and saw the last bang, he said a huge flame came out under the bike and a smell of burning paraffin..! The paraffin vapour was exploding inside the primary casing..! When I parked the bike I notice the very large rubber seal on the Dommie primary had blown out from between the tinware. I’ve never heard anything like it before, and the only explanation we can think of is the alternator might spark if it touches at high revs. That is some force to get that rubber seal out like that as I’d siliconed it on as well.
email (option): horror@blueyonder.co.uk
Friend of mine used to cheat by running paraffin/ oil mixture in various commercials (1 oil to 30 paraffin to give the pump some lube) highly illegal but it was extremely cheap & many people ran the old Di Transits on it for years, anyway I don't know anyone who risks it now we have a 2,500L per year cooking oil allowance.
BUT, point is, he ran a coach on it to Scotland once & the pump was overfueling, so on a long LONG downhill section in Scotland with the engine on the overrun the hot silencers became dense with paraffin vapour & one after the other in a glen with good acoustics exploded, opening up both huge silencers along their swaged seams like bombs, we discussed it & concluded it simply reached a critical temperature, we don't think a spark triggered it. Paraffin ignites at about 200C 
Ah, thanks for that Fred, I couldn't think of a way it could have ignited, but that explains it 
email (option): horror@blueyonder.co.uk
Maybe I can use it as a turbo boost 
email (option): horror@blueyonder.co.uk