Author Topic: T6 Pistons  (Read 326 times)

0 Members and 1 Guest are viewing this topic.

Offline Falcone71

  • Member
  • *
  • Join Date: Feb 2021
  • Posts: 3
  • Location: Romsey, UK
T6 Pistons
« on: 23 Jun 2022 at 19:40 »
Hello all, my name is Nick and I am new to the forum.
I have a 1930 T6 (600cc side valve) in oily rag condition which I have owned for a couple of years, it runs well but has started smoking like an Arial Leader and chucking oil out of the crankcase breather.
On inspection it is in dire need of a rebore. Original pistons with rings seem a bit thin on the ground, I need minimum +30s.
Does anyone have any information on suitable alternative more easily obtained pistons that could be adapted to fit?
Thanks.

Offline eddie

  • Master Member
  • ****
  • Join Date: Mar 2006
  • Posts: 1765
  • Location: Hampshire, UK
Re: T6 Pistons
« Reply #1 on: 24 Jun 2022 at 08:28 »
Hi Nick,
            Allbeit that you have established there is some wear in the bores, I doubt that is the main reason for the sudden oil burning and discharge from the breather. At this stage, it would be worth checking out the timed breather (in the timing chest). It is a cast aluminium disc that runs against the inside of the outrigger plate. The aluminium casting has 2 small lugs that engage with the face of the inlet cam, and they are prone to wearing to the point of not being driven by the cam.
  On re-assembling the engine, make sure the crankcase through bolts are correctly tightened, starting from the left hand side (they also secure the primary chaincase). Then progressively check that everything in the timing chest is securely tightened before fitting the timing cover. It has been known for owners to think all is well when just the timing cover nuts are tight - but that leaves the cam followers and outriger plate loose enough to wriggle around on the through bolts until (usually) the oil feed post snaps off! The extra stress also often results in a cracked timing cover.

  Regards,
                Eddie.

Offline Falcone71

  • Member
  • *
  • Join Date: Feb 2021
  • Posts: 3
  • Location: Romsey, UK
Re: T6 Pistons
« Reply #2 on: 24 Jun 2022 at 08:44 »
Hi Eddie, thanks for the reply. I am aware of the timed breather as mine had worn to the point where it stopped rotating as the lugs on the back were not engaged with the timing gear. I made a new one out of leaded bronze which seems to work fine, and I had to put a helicoil in the thread in the oil feed post as that was stripped.
One thing I forgot to mention in the original post is that the front piston is missing its oil scraper ring from the piston skirt, and there was unburnt oil in the cylinder head on this end. I have carefully checked the crankcase and sump and can find no bits of piston ring anywhere, so I can only assume it was assembled like this by whoever last had it in bits!

Offline graeme

  • Master Member
  • ****
  • Join Date: Oct 2004
  • Posts: 628
  • Location: Hobart, Australia
Re: T6 Pistons
« Reply #3 on: 15 Jul 2022 at 11:18 »
Hi Nick

I had oversize pistons for my S6 made up some years ago by JP Engineering in Adelaide. They weren't so cheap, I think about $150 each at the time, but as I couldn't find any suitable modern pistons I had little choice. They have worked well.

Cheers, Graeme

Offline Falcone71

  • Member
  • *
  • Join Date: Feb 2021
  • Posts: 3
  • Location: Romsey, UK
Re: T6 Pistons
« Reply #4 on: 15 Jul 2022 at 11:34 »
Hi Graeme,

Thanks very much for the reply. Fortunately I am all sorted now. On the recommendation of a mate I took the barrels and pistons to Cox and Turner who are based near me in Hampshire, England and they have (amazingly) managed to source new, old stock, pistons of the correct oversize, so the job is progressing.

Nick.

 

motorcycle