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Ros125 blew up

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Hi all,

had the engine on my Ros125 have a bit of a meltdown, is it possible to get this rebored, looks like only top end damage, the original sysmptim after it cut out mid flight was it had no spark, replaced coil and plug and then had good spark, could the coil breaking down of caused a weak mix to cause this?

thanks in advance




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It might be more due to mixture? I've no experience with this particular type of engine so I can't help you in that respect.

How bad is the scoring though? Can you feel it with you're finger nail? It might be OK once you've got the mixture dialled-in/checked.


Edited by James Troup
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What`s the cylinder like?

Is the cylinder on those engines Nikasil plated?

If so no rebore options.

If the aluminum from the piston has only melted onto the cylinder without damage you might get way with removing the galling with mutiatic acid and fitting a new piston - after finding out why it seized in the first place..

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I had a Ros 125  engine and had same problem. I googled and found a company that refurbished the cylinder ,they built up the scratches rebored and recoated it. this cost me £150 and I bought a new piston. This was years ago and can not remember the company but there were a few. I had one of the first Ros engines in the country from Noel Humphries. They were good engines but once it started to have faults it was never ending so changed to a Moster.  

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Can get the cylinder re-plated - done it a few times, good results.

Check your carb - probably needs to be refurbished with new parts. Replace the internal filter & check the jetting.  Also check for air leaks in the crankcase.

Edited by notch
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