Author Topic: Dragonfly oil leak.  (Read 423 times)

0 Members and 1 Guest are viewing this topic.

Offline chid

  • Member
  • *
  • Join Date: May 2018
  • Posts: 5
  • Location: uk
Dragonfly oil leak.
« on: 01 Jan 2019 at 16:08 »
Hi I have oil spraying out of the timing chest grommet, I tried some silicone round it but it just built up pressure to the extent that the silicone burst and oil blew out over the front mudguard and forks. It also sprays over my legs and as far back as the tool box. I can see from the spares book that there is a breather in there behind the stator but how does it work and where does it breath to?
I tried the LDMCC for a new grommet but I am told they are not available, does anybody know where I can get one, is it the same as used on other vehicles?

Any help would be appreciated.

Chid

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1378
  • Location: Hampshire, UK
Re: Dragonfly oil leak.
« Reply #1 on: 01 Jan 2019 at 20:29 »
Hi Chid,
             The breather is a round plate with 6 holes covered by sprung petals that allow gas out but not back in again. The expelled gases discharge through drilled passages to exit at the bottom of the timing chest. If gases don't pump out of the port, remove the generator cover to make sure the appropriate hole has been punched from the gasket. With regard to the grommet in the timing cover - as you say, they are not available - the easiest remedy is to obtain a grommet that fits the case and then build up the diameter of the generator lead with heat-shrink sleeving until it is a tight fit in the grommet.
   If you also have oil dripping from the underside of the cylinder heads, take off the rocker covers, and then remove the bronze rocker bearing blocks. Under each block, you will find 2 cylinder head retaining studs - remove the nuts and discard the spring washers - replace them with plain washers. Clean the bottom of the rocker blocks and apply a smear of RTV instant gasket around the pockets for the nuts - this will stop any oil finding it's way down the studs and dripping from the underside of the heads.

  Regards,
                 Eddie.

Offline chid

  • Member
  • *
  • Join Date: May 2018
  • Posts: 5
  • Location: uk
Re: Dragonfly oil leak.
« Reply #2 on: 02 Jan 2019 at 19:58 »
Hi Eddie
Thanks for your reply, I have ordered new gaskets but will it be obvious where the hole has to be punched out and why isn't the hole already there? I will start the bike on Sat and see if there are any gases coming out. I managed to pick up a selection of grommets in Halfords today. Will let you know how I get on.
Regards
Chid

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1378
  • Location: Hampshire, UK
Re: Dragonfly oil leak.
« Reply #3 on: 02 Jan 2019 at 20:19 »
Hi Chid,
             If you are purchasing a gasket set, all the holes should be present - it's on home made gaskets that they sometimes get omitted.

   You will probably find that some of the 'oil' that gets sprayed onto the toolbox is, in fact, petrol blowing back from the carb - especially if you make the engine work hard at low revs.

  Good luck with the repairs,
                                              Eddie.

Offline chid

  • Member
  • *
  • Join Date: May 2018
  • Posts: 5
  • Location: uk
Re: Dragonfly oil leak.
« Reply #4 on: 05 Jan 2019 at 10:59 »
Hi Eddie
I have started her up and there is pressure coming out the breather hole. Before I take it apart do you or does anybody else have any other ideas.

Chid

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1378
  • Location: Hampshire, UK
Re: Dragonfly oil leak.
« Reply #5 on: 05 Jan 2019 at 12:21 »
Hi Chid,
             As there is no blockage, the breather should cope with the normal amount of crankcase fumes. Unfortunately, Dragonflies that still have the original split skirt pistons can suffer from excess crankcase pressure. When worked hard, the original pistons tended to collapse, resulting in the ring grooves taking on a wavy form, causing the rings to jam and not seal correctly. When this happens, it is usually accompanied by smoke from the exhaust. The easiest remedy is to fit pistons from the earlier Mark series engines, or the repro pistons available from the LDMCC.
  At this stage, my advice would be to cure the leaks at the grommet and cylinder heads (these are known common faults), and run the bike again to check whether there is any other leakage.

  Regards,
                 Eddie.

Offline chid

  • Member
  • *
  • Join Date: May 2018
  • Posts: 5
  • Location: uk
Re: Dragonfly oil leak.
« Reply #6 on: 05 Jan 2019 at 15:39 »
Thanks Eddie, will have to get some shrink wrap and try.

Chid