Design and build side shaft hit and miss engine from bar stock

[Brian Rupnow]

Engine is running steadily and consistently now, using fuel from it's own tank. Plumbing the tank got a little crazy  but it all worked out well and incorporated my new anti-backflow valve. nothing appears to be leaking. It's setting beside me here on my office desk, running like crazy. Next thing will be to set up the governor.---Brian

[Brian Rupnow]

Doom, despair, and agony on me---the damned purchased anti backflow valve from Sullivan #S756 doesn't work. Not only doesn't it work, but when I called Great Hobbies in Mississauga where I purchased it, they won't send me another one, claiming I have to ship this faulty one back to them at my expense ($11.00) before they will send me a second valve to try. I am at an impasse now. Not sure what to do. Their customer service man is supposed to call me back this afternoon. If he doesn't make me happy, I may drive to Mississauga and pull his arms and legs off!!!

[Brian Rupnow]

I just got the call from Great Hobbies telling me that this Sullivan valve will only operate if there is "back pressure" from the line on the outflow side of the valve, to seat the ball. I think they ---well--it doesn't matter what I think. Fact is, I'm out $35 and don't have a solution to the problem. I can try building another one myself, with a smaller ball (My first one had a 3/16" diameter ball) which may have been too heavy for the venturi vacuum to lift of the seat. If anybody knows of  a source for a purchased anti backflow valve that doesn't rely on back-pressure in the line to make it work, please tell me.---Brian

[michaelr]

Brian you could try a variation on this idea  <a href="https://www.youtube.com/watch?v=vJiA43Mn1D0" target="_blank">http://www.youtube.com/watch?v=vJiA43Mn1D0</a> Make to suit your engine size would cost very little.

Mike.

[Ye-Ole Steam Dude]

I just got the call from Great Hobbies telling me that this Sullivan valve will only operate if there is "back pressure" from the line on the outflow side of the valve, to seat the ball. I think they ---well--it doesn't matter what I think. Fact is, I'm out $35 and don't have a solution to the problem. I can try building another one myself, with a smaller ball (My first one had a 3/16" diameter ball) which may have been too heavy for the venturi vacuum to lift of the seat. If anybody knows of  a source for a purchased anti backflow valve that doesn't rely on back-pressure in the line to make it work, please tell me.---Brian

Hello Brian,

Sorry to hear about the check valve problem and I am sure that you already know this, but with an Inline Check Valve in the vertical position if there is "any" suction from the returning fluid that within itself should close the valve. The guy telling you that it needs "back pressure" is giving you a bit of a run around ( I am being very nice here). If the valve on the outlet side has too much back pressure it would not open, assuming no pressure on the incoming side other than gravity. I think the guy is "BS-n" you. Just my 2-cents worth. Hope you get it worked out.

Have a great day,
Thomas

[Brian Rupnow]

Oh well--You live--you learn!! I did a little research as to why my own check valve didn't work as well as I would have liked. I was on the right track, but I had my check ball setting in a tapered seat, which was cut by the end of a drill. Conventional wisdom seems to be that you shouldn't have a tapered seat. Just a square cut end on the part which the ball sets against. Before assembling, set ball on top of part it seals with and give it one good whack with a hammer. Not enough to deform the outside of the part, but enough to form a very small area which conforms exactly to the shape of the ball which formed it. I will now build another check valve like this.

[Stuart]

Brian

Do not use the ball you set the seat with as the ball to use

Also make up a drift centred drilled to set and strike the ball with

If you are using a SS ball for the valve use a steel one to form the seat

It’s good practice to drill and ream the though hole


Good luck

Stuart

[Brian Rupnow]

Thanks Stuart. I will do that. I broke the shear-pin in my lathe today. I have wondered ever since I bought that lathe what would happen if I ran it past the limits in power feed. Now I know---"SNAP" and that's all she wrote. It has a brass shear pin 1/8" diameter x 1" long between the gear box and the rod that runs along the front of the lathe to move the carriage. I was power feeding towards center, not parallel to the ways. I adjusted the angle of cut, and that moved the cutting tool towards the front of the lathe. I never wound it across manually because I had been taking many cuts exactly the same. Ran out of travel and broke the pin. I have removed the broken pin and will buy a piece of 1/8" dia. brass tomorrow to make a new one. The good news in this is that nothing broke except the pin.

[Stuart]

Brian

Thanks very good news, kudos to the manufacturers to 1 fit a pin and 2 make it the weak link

Stuart

[Brian Rupnow]

These past two days have been difficult. It seems like all of my engine building skills have deserted me. The engine has not ran properly since I put the new gas tank in place. There are a thousand of these small model hit and miss engines out there with the fuel tanks in the base of the engine. They don't have any problem pulling fuel up from the tank, and they don't have a problem losing their gas back into the tank during their miss cycles. There are a limited number of things that can effect these small engines. Compression, ignition, valve timing, strength of spring on intake valve, and fuel delivery. Everything is fine on my engine except perhaps the fuel delivery. I have to try some other things, one being a spare fuel tank set up to be just below the carburetor.---Brian

[Jasonb]

You might want to put a small vent hole in the cap, I can't see one in the photos as the engine won't suck fuel against a vacuum.

[Brian Rupnow]

There is a .039" diameter hole in the cap. I may have put it in after the picture was posted.---Brian

[Brian Rupnow]

Ah Ha--something is rotten in this low mounted fuel tank. Now I have to determine if the engine won't pull fuel up from a base mounted tank, or if it won't pull it up thru my anti flowback valve. I suspect the anti flowback valve to be the culprit. Engine runs just fine on a tank mounted  up very close to the underside of the carburetor. (I said "High carburetor". (I meant high fuel tank.)https://www.youtube.com/watch?v=-ls16yrIf10&feature=youtu.be

[MJM460]

Hi Brian,

So near yet so far.   Is it worth setting the fuel tank on a chair below the bench, connected with a longer plastic tube, and see how much suction you get with that carby while you turn the engine with your drill?  The height it will lift the fuel in the tube, even though it does not reach the needle valve, tells you how much suction is available in the throat.

A throttle plate or even an air cleaner in the air intake would give more suction and so might just help.

It’s a great looking engine, it’s got to run!  And it will.

MJM460

[Brian Rupnow]

The engine would lift fuel up from the tank when cranked with my electric drill. The engine would start with my electric drill, and then run for about one full minute and quit, as if it had run out of gas. Current theory is that the venturi created vacuum was strong enough to lift the fuel up from the tank when the drill was driving the motor, but when the drill was taken away the venturi created vacuum wasn't strong enough to keep the 3/16" steel ball off the seat AND suck the fuel up. I have taken the 3/16" steel ball out and substituted a 1/8" diameter steel ball--and yes, I give  the 1/8" ball a whack with the hammer to "seat" it in the end of the tube, then discarded that ball and put in a new one. Loctite on the two sections of valve is drying as we speak, and in half an hour we will try that lower tank again.