Sidevalve Single

[Richard Evans 6Participant @richardevans6]

Hi All

First engine build here and I'm hoping for some advice from the experts.

I have just finished an own designed sidevalve single around 11cc. So far it starts very easily and turns a 12.5×6 at 7000rpm but I'm struggling to get it running smoothly and it feels like its got a bit more to give. I suspect its a mixture issue. I have tried 2 completely different carbs without success but I don't have any idea what size bore I should use. I initially used a twin needle carb with a 7.5mm bore. If the throttle was opened all the way it would rev up and then die like its not drawing fuel, even with the needle valve completely open a pinch test showed it was lean. I then tried a single needle carb with a bore of 6.5mm and could not get to the same top rpm at any needle valve setting. I can lean it out with the needle till it gets peak rpm and if I go any further it dies yet when the tank runs out it smoothes out and runs best for a couple of seconds.

I have also noticed a loss of power when the glow driver is removed at any rpm.

My plan is to refine the design and build some multi cylinder engines. I might even sell some. I just need good reliable performance.

the full spec of the motor is:

Bore: 24.65mm

Stroke: 24.00mm

Compression: 9/1

Valve lift: 1.9mm

Ex open: 61 deg BBDC

Ex close: 31 deg ATDC

In open: 25 deg BTDC

In close: 67 deg ABDC

Glow plug: OS F-type

Glow plug location: Bore centre

The main variables that I think need looking at are the compression ratio, Glow plug location and carb type/diameter but I could be completely wrong.

Any advice would be very welcome.

[Richard Evans 6Participant @richardevans6]

[Neil WyattModerator @neilwyatt]

I'm no expert, but I understand four-strokes generally need hot plugs as they have to keep hot for twice as long between firing.

Neil

[Richard Evans 6Participant @richardevans6]

Hi Neil

Thanks for that.

The OS F-type is a hot plug specially for four strokes. I have also tried hobbyking no3(hot) and enya no3(hot) plugs. The OS works the best so far but none are perfect.

[Ady1Participant @ady1]

You probably need a more specialised site than here

Ron is dead now but there are are lot of engine heads out there who know tons of stuff and have their own sites/forums

[JasonBModerator @jasonb]

Several of the "Motor Boys" post on MEM forum as well as quite a few others who build aero engines.

Ady and anyone else interested another of the Motor Boys Adrian Duncan has now started a similar site to Ron's which can be found here

J

[Ady1Participant @ady1]

Thanks Jason

[Richard Evans 6Participant @richardevans6]

Thanks for the info mate.

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