cylinder walls wear

[ED2.4]

Hello all,
i need some advices cause i have some troubles with my last project,
i recently built a 2542cc( oxyboxer ,and after the break-in period the engine began to produce a deep white smoke,
after the teardown ,everything looking good except barrels and pistons, there was a lot of wear all around the cylinders walls and the pistons skirts, for engine has lived 1 hour !
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barrels are 4"AA products and pistons are Venolia from Pauter,

i re-honed the walls to the max Venolia specs (0.007"),there was already 0.005" before ,job done with torque plates and a true Sunnen honing head,

when i re-start engine ,same result and observations....

after some test:
leakdown test was good (under 5% ) ,
scratches of walls wear are not deep ,i don't feel them with my nail,
and compression are extremely hard to pass by hand!
barrels bottom skirts are very long(40mm), so pistons guidance is integral at BDC
rings gap still right,
and the wbx case is vented everywhere including on rear(1/3 cylinders),
valves box covers vented too ,

i don't understand where oil come and pass ?
heating problem?

so now i have no more ideas of problem cause ?
thanks in advance for your advices and ideas

Eddy

[drgouk]

What were your ring end gaps?

[ED2.4]

Hi,
Total seal instruction sheet say : Bore in " x 0.0045 for top and x0.0035 for  second  ,so there is  4.003"x0.0045= 0.0180135 " (0.45mm) and 4.003"x0.0035=0.0140105" (0.35mm)
thanks

[j-f]

Too much valve stem clearance?

[ED2.4]

Hi,
valves clearance seems to be correct ( 0.05mm) and heads are new
thanks

[Nick]

Are the carbs close or do they maybe flow over (Fuel weakening the oil ?)?
What Oil ?

[ED2.4]

Are the carbs close or do they maybe flow over (Fuel weakening the oil ?)?
What Oil ?

Oil is 10w40 synthetic,
if you mean  float flooding ,i don't think ,no leaks in the bores and  jetting is on the lean side ,one of my first though was a cylinder wall washing by fuel too, but it's happen in a 30mn time , very fast , but maybe?
will re-check my carbs,
thanks

[dangerous]

Double check that NONE of your oil ring expanders have over lapped.

Also look for any holes between spring seat and inlet port.
...or other casting/breather issues that will allow oil into the chamber.

[dangerous]

If this is turbo? ,
then make sure your drain is adequate
and that you have restricted the oil supply to the turbo.

[ED2.4]

Hi Dangerous ,
it's a N/A engine, MS230 are new so no cracks or something else wrong on the heads ,oil ring expenders are in place ,not overlapped or broken

thanks

[dangerous]

White smoke is oil. (or water! ha ha!).

While your bores are a little ugly, I have seen worse that did not use oil.

Keep looking and measuring, even with things you have already checked.

It should be quite obvious as to the cause, often it is the simple things we overlook,
because we cant beleive it to be something so simple.

While is is likely unrelated, those ring gaps seem a little tight to me, especially the 2nd ring,
since gases trapped between the tow rings will unload the top one.

[Mike Lawless]

I used to try to go by standard ring gap recommendations. And the rings would butt solid. In an aircooled motor, the cylinders are much hotter than a conventional motor, so the gaps must be wider. Probably .025 to .028" on the top and second rings. Pat at CB clued me into this a few years back.

When the ring gaps butt, the rings are not longer round too.

[ED2.4]

Thanks for your replies guys,
yes i've been surprise by second ring gap instruction too, especially with a gapless ,
  0.025-28" looks huge! but Pat knowledge is huge too ,will try wider with Pauter cylinders ( that i have) and  a reasonable clearance between P/C ,around 0.005" sounds good,
i 'll inspect rings ends too
thank you