Can someone help identify these 2 engines? the last pic is a Quadra35 or 40 Quadra. Has a 18x8 prop on it. Serial # is 40402.

the other 2 pics are a us engine but don't know what size, serial # 003713. Looks to be about the same size as the Quadra.

Picture 3 of 4 is a Quadra or a US Engines 35cc or 41cc engine as both had rear exhausts.
Pictures 1 of 4 and 2 of 4 are a US Engines 25cc as they had a side exhaust.

Ok thanks. I know that it is a Quadra as it has a sticker on the side of the case, is There anyway to tell if is a 35 or 40? I wasn't aware that US Engines made a 25cc. Only heard of the 35 and 41.

Your Quadra is a very old one? Very old ones have points and there will be wires coming from the inside back of the flywheel. See the wires in the picture?

1 ring = 35cc, 2 rings = 40cc. The newer 40cc has 1 ring

Look at the serial # on the bottom? It may start with a 35 or a 40? Some SN's were like 409816 which would be Quadra 40, 1998, 16th week?

Serial # is 40402

So now we know it is a Quadra 40 without looking farther?

I reckon so. Thanks

The US 25cc was not the greatest performer so don't expect a lot from it.

I have a quadra 35 with nospark all it has is a coil and a kill switch does it need a module or is it buil in to the coil, the coil has a hump on it wher the kill switch plugs in , also the crank has no cam for points but there is three screw holes to hold points plate possibly, this engine is mounted on an old byron pitts and looks like the stock mount and engine sold by byron yars ago any help would be great thanks.

This engine is likely complete. Why not see if it'll make a spark in the spark plug?

If you remove the spark plug from the cylinder and ground it to the outside of the engine with the wire attached, you should be able to easily spin the engine fast enough to make a spark?

The "newer" Quadra's had trigger coils triggered by the flywheel. A different coil than the older ones where a standard coil was triggered by the points.

Well thats how checked for spark in the begining also I have aspark check plug with a clip on it made just for this test, my problem was no spark so I eliminatedthe kill switch still no spark next test the coil ohm in 4000 range should be good, so possiby the trigger I was thinking and thats why I came here for some insight about the ignition module,,,,,,,,,,,

The internally triggered coils are either they work or they don't. Might look for another coil?

I had a Homelite with a erratic coil. Found a coil that looked about right in a junk box at the chainsaw store. It's been running ever since.

Get a multimeter and check the resistance of the coil. Set meter to 20K resistance. Red test lead to spark plug boot wire and black test lead to the positive lug on coil, Should see 2 to 5 on meter,
Keep red lead in boot and move black lead to the ground lug. Should see 2 to 5 on meter.
Keep black lead on ground lug and move red lead to positive lug. Should see 0.1 to 0.2 on meter..

Also , check the flywheel to coil gap. If it's too large it won't trigger. Put a business card in between the magnets, loosen the coil bracket and adjust the gap to that thickness.

You'll never see the spark in broad daylight, take it into a dark closet, also there is a minimum RPM required to generate a spark, the spring starter should do it, not everyone can finger flip one fast enough.

Well tried to sart the old quadra year day but never could get a spark. I'll check the coil and points per the previous posts tomorrow.
what prop and rpm should I be looking for? Had a dynathrust. 18x8 on it

any idea on prop for the us 25cc? Would 16x8 be ok

Ok just checked my coil. With my meter on 200k my fading with + in boot and - on pos or neg lug I get 7.2 ! When I touch pos to pos lug and neg to neg lug I get 0! I did notice when I flip the prop as the magnet passes the coil I get a reading but it goes away. Am thinking this is the pulse. In the pulse coil. What do y'all think?

You are seeing "0.00" between the lugs? Move the meter selector to a lower resistance scale(20K, 2k, 200) and see if you get any reading other than 0.00,

Yep, just checked again. I'll have to find another meter to try below 20k. Thats as low as mine goes

any idea on prop for the us 25cc? Would 16x8 be ok
Got mine mounted in a Great Planes Super Stearman. Initially ran an APC 17 x 8 which is fine but going to try a 16 x 10 as it gets more run in. Very scale like performance, ie fairly lazy and gutless, but great for stooging around. Spring starter is a nice idea and works well but no choke is a pain on an enclosed engine. Even going full throttle with ign off for a few turns will not put enough fuel into the motor to get it started. Midway through swapping the original carb for a Walbro clone with a choke.

Ok thanks guys tried a coil off of a weed wacker and wala spark is good thank you learn somthing new every day!!!!!!!

This engine's best power range is in the 7000 rpm range so prop accordingly for the best speed range of your airplane while keep the engine rpm not far above or below 7000 rpm.

I have a Quadra 35 that was running great in my 1/4 scale Sopwith Pup. Last fall I was out at the field and had a nose over on landing. Had to replace the prop and some minor damage.
I went to start the plane and got what sounds like a miss fire when you advance the throttle. It will start fine and idle great, But when you advance the throttle and leave it any setting
above idle it has what sounds like a miss fire. It also shows up on the tack. An other thing it does know is I believe to be some kind of interference with the radio system. With the engine
off the flight controls work fine, With the engine running my flight controls are moving on there own and its not slow either. I have rebuilt the carb with no difference. Any help would be
very much appreciated.

I would change the plug and make sure it's a resistor plug. Some brands claim to be a substitute to the original but are not resistor plugs. Make sure the plug cap is in good condition and is tight on the plug ....some add a hose clamp to keep it secure. Next would be a coil swap.

looking to use two 40 cc Quadras on Ziroli DC-3 but theb springs starters will have to be removed, any problems ? I am just mystified to find the throttle and or how to make them work these are older new engines thanks, Kevin in Denver