Odds & Ends engine

[Gordon]

I have just completed the building of the Duclos Odds & Ends engine. I have it running making it pretty much per the original plan including the carburetor. I had trouble getting it to run unless I partially closed the carburetor intake. I ended up putting a restricting tube in the end of the carburetor with 9/32 OD x 5/32 ID and that seems to let the engine run. If I remove that I cannot get the engine to run. I have decent compression and the valves seal OK. As far as I can determine I do not have leaks at the intake/exhaust manifold. I have put gaskets at the manifold. In looking as other builds a lot of folks use a different carburetor than the original Duclos.

Anyone who has built this engine have a similar experience?

Gordon

 

[a41capt]

I have just completed the building of the Duclos Odds & Ends engine. I have it running making it pretty much per the original plan including the carburetor. I had trouble getting it to run unless I partially closed the carburetor intake. I ended up putting a restricting tube in the end of the carburetor with 9/32 OD x 5/32 ID and that seems to let the engine run. If I remove that I cannot get the engine to run. I have decent compression and the valves seal OK. As far as I can determine I do not have leaks at the intake/exhaust manifold. I have put gaskets at the manifold. In looking as other builds a lot of folks use a different carburetor than the original Duclos.

Anyone who has built this engine have a similar experience?

Gordon

I haven’t built it yet, currently working on Rudy’s non-compression engine, but once that’s done I’ll probably start on it.

I’ll watch your troubleshooting closely!

John W

 

[Gordon]

I haven’t built it yet, currently working on Rudy’s non-compression engine, but once that’s done I’ll probably start on it.

I’ll watch your troubleshooting closely!

John W

I have the engine running after the usual tweaking. It still only runs with the restrictor in the intake of the carburetor. Not sure why but as long as it works I am going to just leave it.

 

[Richard Hed]

I have the engine running after the usual tweaking. It still only runs with the restrictor in the intake of the carburetor. Not sure why but as long as it works I am going to just leave it.

can you show a photo of this 'restrictor' and the carburetor?

 

[Gordon]

It is just a 5/32 ID x 9/32 OD x 1/8" lg tube placed in the intake throat of the carburetor. Nothing exotic. Just a permanent choke.

 

[Richard Hed]

It is just a 5/32 ID x 9/32 OD x 1/8" lg tube placed in the intake throat of the carburetor. Nothing exotic. Just a permanent choke.

obviously it is not getting enough fuel. What are your options?

 

[Gordon]

Obviously there is not enough velocity at the jet to draw the fuel from the tank and atomize it. The throat diameter at the jet is 1/4" with 9/32" at the intake. I would guess that if the carburetor was built with 7/32" at the jet and 1/4" intake it would work better. By restricting the intake I am creating more velocity. It works now so I am not going to remake the whole carburetor to prove that the smaller throat would work.

 

[Richard Hed]

Obviously there is not enough velocity at the jet to draw the fuel from the tank and atomize it. The throat diameter at the jet is 1/4" with 9/32" at the intake. I would guess that if the carburetor was built with 7/32" at the jet and 1/4" intake it would work better. By restricting the intake I am creating more velocity. It works now so I am not going to remake the whole carburetor to prove that the smaller throat would work.

what about a needle valve? can you adjust that? Or can you simply open the jet by a tiny amount? That wouldn't require a whole rework. or maybe shorten that 1/8th hole to 3/32?

 

[johwen]

It is just a 5/32 ID x 9/32 OD x 1/8" lg tube placed in the intake throat of the carburetor. Nothing exotic. Just a permanent choke.

Most likely the spring setting on your governor is too light meaning the engine speed is too slow for the larger choke diameter. Air speed through the venturi
Is too slow to drag in fuel. Tension up the governor weights so the engine runs a little faster and see what happens. I made one more than 30 years ago and then sold it for $1500 Cheers John Hope this helps.

 

[AndrewW]

I have just completed the building of the Duclos Odds & Ends engine. I have it running making it pretty much per the original plan including the carburetor. I had trouble getting it to run unless I partially closed the carburetor intake. I ended up putting a restricting tube in the end of the carburetor with 9/32 OD x 5/32 ID and that seems to let the engine run. If I remove that I cannot get the engine to run. I have decent compression and the valves seal OK. As far as I can determine I do not have leaks at the intake/exhaust manifold. I have put gaskets at the manifold. In looking as other builds a lot of folks use a different carburetor than the original Duclos.

Anyone who has built this engine have a similar experience?

Gordon

Hi Gordon
I made a Philip Duclos odds n ends engine in 2021. It's exactly as per the drawings and runs really well. I don't understand how others have used a different carb, as its an integral part of the valve assembly.
Have you got the fuel tank outlet level with the carb inlet? If not, that could be the problem. I've attached a pic of mine.
Check out my YouTube series of the build (@learningturningmetal), which might help.
I also put a gasket on the manifold as that appears to be a weak element of the design.
Hope you get it sorted.
Andrew

 

[Gordon]

Finally found out why the engine was not running well. The exhaust valve was hitting the intake valve at the top of the exhaust stroke. I took some off from the face of the intake valve so that they did not hit. Much improved. They were only hitting by a few thousands but that was enough. FYI: The two valves are facing each other at 180° apart.

 

[oldengineguy]

Funny to see a post about the Odds & Ends engine to-day. My Dad built one in 1986 when the magazine artical first came out. It never did run well and Dad moved on to other engines. I made one , mostly to the drawings in1998, the biggest change being that I made it of aluminum instead of steel ,and it runs well. Yesterday, with nothing else to do, I got out Dads old engine to see if I could make it run. Biggest problem seems to be low compression and found ring gaps to be way too wide (035 thou) I was in the process of making a new piston for Viton O rings when beer o clock came and time to look at HMEM and saw this post. I agree with Andrew W the fuel level is critical to have it run well. I'll update when I get the new piston installed.
Colin

 

[AndrewW]

Funny to see a post about the Odds & Ends engine to-day. My Dad built one in 1986 when the magazine artical first came out. It never did run well and Dad moved on to other engines. I made one , mostly to the drawings in1998, the biggest change being that I made it of aluminum instead of steel ,and it runs well. Yesterday, with nothing else to do, I got out Dads old engine to see if I could make it run. Biggest problem seems to be low compression and found ring gaps to be way too wide (035 thou) I was in the process of making a new piston for Viton O rings when beer o clock came and time to look at HMEM and saw this post. I agree with Andrew W the fuel level is critical to have it run well. I'll update when I get the new piston installed.
Colin

Hi Colin
I hope you manage to get your dad's old engine running. I seem to recall that the most difficult bit for me was cutting the valve seats. I think I decided to change the design a little and made some valve guides to press into the 'head'. I should complete my Jerry Howell v-twin soon and I might just have a go at another Duclos design next. I must investigate.
Cheers
Andrew

 

[Steamchick]

Just picked-up on this thread. Gordon, your first post seems to answer your question.
The restrictor naturally increases the velocity of air in the carburettor, which in turn increases the suck of fuel. So you get enough fuel for the engine to run.
Remove the restrictor and the carb loses "suck" so you get less fuel and it won't ignite.
Simple question, do you want a running engine for Demonstration, or a "power machine" to power a generator, water pump, etc.?
I would keep it with the restrictor. - Who cares?
As to all the other ideas, "Very clever" is my opinion. More fun "ringing the changes to improve the engine. But Post #11 seems you found another glitch and have resolved that one.
A very worthwhile thread.
K2