Hello from Texas!
My Flyer starts ard runs very well, but backfires through the right side door on trailing throttle. Am I too far advanced? I backed the timing off a bit, but it did not seem to help. The door eventually blows off.
I don’t know how far Texas is from Rothwell, but “flying crankase doors” might be the what are giving rise to the U.F.O. mysteries we keep hearing about.
Any road up (as they say in Birmingham) sounds like a very weak mixture and/or a leak in the exhaust system.
Run the engine slowly as possible and squirt petrol around the joints. If the engine picks up, its drawing in air (and your petrol).
Thanks for the response Stan. I doubt that my flying disk has enough altitude to be picked up on radar…
You are probably correct on the air leak. I will check it tonight. I have 6 holes on the underside of my cases. One is pluged with epoxy, 2 have screws as plugs, and the other 3 are open. There is also a small hole on the lower right side edge of the cases. These holes are not cracks, but are all neatly drilled. Do these open to the crank? Would it be ok to seal them all with epoxy or do they serve some other purpose?
Could this be my problem? I think that there should be a reverse thread nut at the end of the crank. Could this nut come of with the rod in place? I could find no sign of the nut.
or just go to this address to see the photo
I’m mystified by your rematks of “holes” in the crankcase. Dependant upon year the maximum “input points” (I.E. “holes” in the crankase) are the oil inlet from the pump/drippers, and a drain plug.
If you have surplus drilled holes, someone has been buggering about.
The standard crank bolt should be “locked” with a left-hand threaded nut – but if there is no material damage inside the crank chamber, chances are the person who biult the engine left it off. Lets hope he slipped whilst drilling the crank case holes and stabbed himself.
Nice pic! These digital camera’s are a real boon when you want to convey this sort of info.
LH lock nuts
I never use them.
If you knock up the crank properly, you will never need it.
My new cranks use a cap screw and no locknut.
I am sure you have researched the subject of crank assembly, but in case you fancy a refresher, click the link–
As regards air leaks
1) If the seating face for the door has been broken where it is thin at the rod loading position, this can be a problem.
2) Be sure there are no air leaks from transfer port gaskets.
I have known them to break where you cannot see and leak air badly. The alignment of the transfer port seating faces on the block and case are often not in good alignment and so do not grip the gasket properly, hence them breaking.
I do not use gaskets. I just degrease and seal with RTV silicone, usual K mart stuff you use round baths.
I use the same to seal barrels into crankcases. In fact, to be honest– I do not usually use any Scott gaskets in my engines. And– they still work!!!!
Stans idea to spray petrol is good and should pin point the position of the problem.
One extra tip–
Do not smoke while you do it!
Roger, has your use of “bath sealant” a Fruedian connection with Alfred having originally dreamed up the concept of the Scott whilst lying in his bath???
Thanks Roger and Stan, all seems to work well now.
I cleaned up the gasket surfaces well and made sure the door was back on tightly. I am using a normal, un-sholdered nut as I lost the correct one. I used a small bolt in the door strap groove to stop the strap sliding down, which may be helping keeping it on tightly. I need to order the correct nut.
Thanks again for the help.