Author Topic: Dragonfly of dispair Smoking barrel  (Read 527 times)

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Offline AndyMorgan

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Dragonfly of dispair Smoking barrel
« on: 10 Jun 2020 at 17:50 »
Any advice please
My rebuilt Dragonfly engine is very smoky on the left hand pot and I get an oily plug running for 10-15 minutes the smoke doesn't clear, much more and the shed becomes a health hazard.
It has been rebored to 63mm with oversize honda 250N pistons on both bores to clean off a significant amount of corrosion, this engine was a basket case, Both ring gaps are good at 0.01" and only the left hand is smoky. New gaskets and  the head doesn't seem warped or cracked.
Any clues, things to try or experience of treating similar cases.

Cheers

Andy

Offline oily bloke

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Re: Dragonfly of dispair Smoking barrel
« Reply #1 on: 10 Jun 2020 at 18:17 »
Its possible that one of the rings is upside down or oil is getting past the guides. Probably the former.

Offline eddie

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Re: Dragonfly of dispair Smoking barrel
« Reply #2 on: 10 Jun 2020 at 18:36 »
Andy,
           Do you know what pistons are fitted to your engine? Are they genuine Honda or pattern pistons? I have used both types in the past, and genuine pistons are much better quality. Also, carefully check the ring widths - some pattern rings are of a slightly different width, so could be pumping oil.

  Regards, Eddie.

Offline AndyMorgan

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Re: Dragonfly of dispair Smoking barrel
« Reply #3 on: 11 Jun 2020 at 14:25 »
Thanks,
I got Hepolite pistons so guessing they're not genuine Honda parts.
I will swap the pistons over and see what happens but pretty sure the rings are right and the right way up, will do a side by side comparison to check.

Cheers

Andy

Offline AndyMorgan

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Re: Dragonfly of dispair Smoking barrel
« Reply #4 on: 12 Jun 2020 at 19:46 »
On side by comparison the smoky barrel piston top ring appears much more rounded slightly shiny just in the middle compared to the others non smoky barrel flat surface. Seems I have an odd ring. So good to get to the bottom of a problem, now where to get AE piston rings for 62.5 (I made a mistake earlier as the rebore was to 62.5 not 63.0)

Photos
1) smoky barrel top ring profile (rounded)
2) non smoky barrel top ring profile (flat / beveled edge)
3) both rings top surface AE ring non smoky, N50 ring smoky.
« Last Edit: 12 Jun 2020 at 20:05 by AndyMorgan »

Offline dalgrae

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Re: Dragonfly of dispair Smoking barrel
« Reply #5 on: 13 Jun 2020 at 13:51 »
Hi try Cox and Turner in Somerset

Regards. Colin

Offline Vermont-Ian

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Re: Dragonfly of dispair Smoking barrel
« Reply #6 on: 14 Jun 2020 at 15:36 »
Another possibility - oil gets in via worn valve guides or valve stems.  (From personal experience).
Ian Stokes
Richmond, Vermont, USA
1948 Mk III
1936 Citroen 'Traction' 7C

Offline oily bloke

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Re: Dragonfly of dispair Smoking barrel
« Reply #7 on: 14 Jun 2020 at 16:34 »
Personally I would have bought genuine Honda if I could find them. Start with Dave Silver Spares.
Good luck

Offline AndyMorgan

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Re: Dragonfly of dispair Smoking barrel
« Reply #8 on: 16 Jun 2020 at 20:16 »
Problem appears to be solved. Many thanks

Andy

Offline Jonathan Hewitt

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Re: Dragonfly of dispair Smoking barrel
« Reply #9 on: 17 Jun 2020 at 08:06 »
Good morning, so what did solve the problem ?
  Jonathan

Offline otaio26

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Re: Dragonfly of dispair Smoking barrel
« Reply #10 on: 17 Jun 2020 at 11:45 »
Agreed,I would like to know your solution to the problem,as I had similar problem.

Offline AndyMorgan

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Re: Dragonfly of dispair Smoking barrel
« Reply #11 on: 17 Jun 2020 at 15:13 »
New rings