Duclos hit and miss engine.

[Master]

Engine starts easily and very reliable. Made it about 20 years ago. Problem is when it fires it jumps around on the table. My friend made same engine and it just runs along very smoothly. Possibly firing is off?

 

[Brian Rupnow]

Probably it is the ignition timing. I built that same engine about 10 years ago, and it is a great build. I find that ALL of my engines jump around on the table if they are not bolted down.

 

[kuhncw]

I agree with Brian. Check the ignition timing as it may be advanced more than necessary. I time my hit and miss engines just three or four degrees before TDC.

Higher than necessary compression ratio will also make an single cylinder hit and miss jump when it fires. My engines seem to run well with 4 or 5 to one compression ratio.

Chuck

 

[Master]

Thanks. I think I timed it a bit after TDC. Easy fix. I'll let you know the results.

 

[Sprocket]

If timing doesn't solve the hopping, try adding some weight on the flywheel on the side opposite the crank throw. While the flywheel may be balanced, I think the crank puts it out of balance, thus some hop. It's worked for me.

 

[Master]

I did change the timing. Runs much better and seems to use less fuel. Still hops around tho. Extra counter weight sounds logical. I've made four of these engines and enjoy their simplicity.

 

[Brian Rupnow]

Like all hit and miss engines, if you get it to idle really slowly, it will hop every time it fires. I think that is why so many small hit and miss engines were mounted on a wheeled carriage. When the engine fired, the wheeled carriage would move slightly and then settle back into position.