Hitchcocks Forum

Dear Bulleteers,

As a Bullet newbie, can somebody help me diagnose a problem I had today?

Whilst on a long ride, with the engine fully heated up but not running that fast (40mph), I heard a loud pop. I pulled over and saw that oil had been spattered out from all around the seal of the primary case. I hope I have the right terminology: by primary case I mean the left hand side big case that contains the clutch. There were even oil splatters on the underside of the tank, as well as drips coming from underneath the primary case, and lots of oil dribbling down the side stand.

What could have caused this? And how should I fix it?

Many thanks for your advice.

Dave

I had that happen once. It was due to the alternater creating a spark and igniting the vapour in the primary case. Buggered the cover which was fortunately cheap to replace. Make sure that your alternater rotor isnt rubbing on the stator.

daveh - Please tell us what model/engine size/year and we can perhaps make some educated suggestions.

Damaged crank case drive shaft seal?

Simon, what oil were you using in the primary case? I ask because although I have heard of this blow-out happening before, the usual explanation is that it is petrol vapour being ignited, presumably from a flooding float chamber. That seems unlikely to me, the quantity of fuel would have to be huge to dilute the oil that much and in any case, how would it get into the primary case? The examples I have heard of are all credible rather than a bit of car park gossip so I wonder if ATF is more flammable than the originally recommended 20w?

REgards, Mark

I was running ATF but I had washed the cases clean with white spirit a few days before so I assume there must have been some volitile vapours left from that. It was a bizarre occurrence but apart from a cracked outer cover there was no other damage.

It might pay to drain the case and remove the cover, then run the engine in the dark to look for any sparking from the alternator.

Thanks Simon, that's both informative and worrying as I have just washed the interior of the primary case on the Oily Rag Interceptor with de-greaser! Leon's suggestion is a good one, it would only take a bit of swarf between the rotor and stator to cause a spark.

REgards, Mark

FYI - I took off the primary chain case and found the alternator was rubbing very badly. That must have created a spark. Had to replace the alternator stator. Thanks for this helpful suggestion!

There was no problem with the crankcase breather. And the seal around the primary chain case seems to have survived.

I'm not sure whether it was ATF or engine oil in there, as I only recently bought the bike.

The model/year: bullet 350 from 2001.

When you get round to replacing the stator, a broad ring cut from an empty fizzy drink bottle makes an excellent spacer to ensure the gap between stator and rotor.