Member postings for william cubbon

(I used Message member, but notice I can also post a reply which will now do.!)

Thanks for your lapping suggestion, Google price is ok for workshop budget. Silicon carbide should correct 15/32ins diam cylinder bore surface condition suffering from uneven wear and possible distortion, the cylinder material is hardened steel. A new piston will of couse also be required.

Thanks Jason for promptness. Long thread is really good. Am now reminded of Ramon's ME articles in 2014 in particular ME No 4484. 1000g SC, you recomend, will now enable me to purchse on line - thanks. Patrick Cubbon.

I have a Milford Mite 1.4cc cylinder now built into a petrol 2 stroke. Poor compression requires the bore surface to be lapped and a new piston to match.

What lapping compound would the forum recomend, ie grit size. The steel cylinder is hardened.

Thanks for any response.

Patrick Cubbon

Just to close this forum thread. Re positioning spark plug made no difference. Engine remains a non runner. Problem is LEAKY inlet and exhaust valves with little compression. New valves, re-machined seats, and better cams needed. The challenge presented with this engine was to complete the build and then see if it was a runner. The engine moves to display only! Now it is a return to steam - a single cylinder version of Bertinat's Borderer ME 1989 issue 3862. A year has passed playing about with this engine and an enjoyable time spent in the workshop.

Hi Howard, Felt pad above petrol - thanks for a good suggestion. First rushed attempt with surface carb was not a success. Vibration resulted in a haze of petrol droplets from the exhaust. Blutac, to secure plastic pipe into tapered mouth of emett carb, does not take kindly to petrol! Next step is to be more professional with a remote petrol container and plastic feed pipe directly into inlet port via a proper adaptor. Still to be done is to position the spark plug gap within the combustion space. The engine has a reprieve from under the bench for now!!

Problem engine, thanks JasonB for photo guide input, quite a bit of time for the result to appear.

David standing - canon/cannon that really provoked more than a smile a real laugh!

Will be pressing on with a vapour bottle, the photo shows petrol supply to a Nemett carb. on the other side.

Patrick Cubbon.

MichaelR - air bleed in the intake - a sensible idea

Neil Wyatt - wire mesh as a flash arrestor, a good suggestion thanks, reminder not a pressure vessel. Flame thrower! I am older than you, in the 50's gunpowder ingredients could be purchased from the chemist - my friend was able to fire ball bearings from a small brass canon, me - lit some powder in the fireplace (Father not aware).

PGK - 2 to 3ft flame out thanks for the warning.

Hi Howard - Yes, I have a copper tank that could be used though I like to see what is going on with petrol levels. Wished to add a picture of the problem engine for general inteterest but did not succeed. I see MichaelR managed with his photo.

Thanks to Brian Sweeting and JasonB who suggest experience with this form of carburation presents little risk. The problem engine was given part finished as a challenge to complete. Numerous adjustments to the carb and ignition timing failed. However, the plug needs deepening to ensure the spark is within the chamber, then, combined with petrol vapour success may be the prize? If not it is back under the bench! Thanks for the mention of Jan Ridders and his web link.. Patrick Cubbon

What risk of flash back explosion might exist by adopting a glass jar petrol vapour carburetor? The engine in question is 1 inch bore, 4 stroke, with Hall effect ignition operated at crank speed. Petrol vapor will be drawn to the air inlet of a Nemett designed barrel throttle carb through a clear plastic tube. Of concern is possible leaky valves, valve overlap period, valve timing events in general, and also the extra spark in the valve overlap period. Thanks in advance for any comments. Patrick Cubbon