Hodgson Radial - won't run

[Jon James]

WOB,

Thank you for your advice.

Regards,
Jon

 

[mayhugh1]

Jon,
So, are you using a Hall device for the trigger or are you using points?
Terry

 

[Jon James]

Hi Terry,
Yes, I am using a Hall device from S/S, which is Roy Sholl.
In a previous post in this thread, Roy suggested a modified distributor cap, basically a cap with no sides so that the rotor and contact are actually visible. This should leave no unwanted path for the spark to follow. I am making that now.

If this doesn't help, it leads me to think it is a carb problem. A previous post in this thread suggests the Perry 4600 carb (recommended by Lee) is too big. He suggested a smaller Traxxas carb which I have on order.

As always thank you for your thoughts.
Jon

 

[Jon James]

My cap is Acetal from Mc Master. As I said earlier the spark passed right through the rotor to the shaft. So I bought some UHMW from them because the product detail said it had much higher dielectric strength and was an "excellent" insulator. So before I went to the work of making a new cap from the UHMW I did a similar experiment and the spark passed through it also. Crap!


So per Roy Sholl of S/S CDI ignition, I made a cap with no sides. Basically a Acetal plate 3/8" thick with the brass contacts protruding from the top and flush on the bottom. I supported it with 5 /8" standoffs. It sits about .010" above the rotor contact. I remade the rotor contact from a piece of printed circuit board about 3/16" wide, with a blob of solder to make the center contact. I glued the contact to the rotor, not screwed. Thus, the thickness of the PC board contact adds an extra layer of insulation. No where for the spark to go except where it should.
The rotor is visible from the side. I can actually see the rotor contact passing the contacts in the plate. I can see a ring of fire as it runs. Fun to watch.

Unfortunately, it still barely runs. Now I'm back to thinking carb. Awaiting arrival of a smaller Traxxas 4033 carb, as recommended in a previous reply. I hope that is it.
Jon

 

[mayhugh1]

Are you sure your fuel tank and crankcase are ventilated? The crankcase is best ventilated thru the scavenger pump with a small hole in the oil tank cap.

 

[rsholl]

Jon, what fuel are you using? Lee's engine will run with the Perry 4600 carb. I'm not a big fan of Coleman fuel and last check on price looks like it is getting too expensive. My first go to fuel is 100LL av-gas if it is available in your area. I'm lazy and run my RC aircraft fuel which is E-85 mixed with Klotz oil at 32:1 (did I mention I was too lazy to mix fuel for the little engines so just use my regular RC mix). I have also done some running on the pre-mix sold for the chain saws and trimmers. I prefer the 40:1 mix and the best place so far has been TSC.

https://www.tractorsupply.com/tsc/product/trufuel-40:1-pre-mixed-fuel-32-oz?cm_vc=-10005
If you use the av-gas add one of the 1 gallon 2 cycle mixes to a gallon. Most brands are now using 50:1 which is fine. As for the carburetor, remember we are dealing with an alcohol (which is 3 times more dense than gasoline) design. I have not had the time to try and figure out what needle tapper would better suit the gasoline best but the needle setting will definitely need to be much leaner than what is stated for the Methanol fuel the carb was originally designed for. 40 or 50:1 will give you good top end lube and I'll guarantee it will not effect the operation or performance of any of our model gas engines. The Traxxas 4033 carb should work just fine too. It is almost impossible to put too small a carb on an engine and if you did, all it would do is limit the top end for speed. I believe the Perry 4600 is the same bore as the Super Tiger .60 size carb the guys were using when it was available. It will be good to know if the smaller Traxxas carb works better than the Perry 4600. Glad to see you are making good progress, keep it going.

 

[JP2]

Jon, Like you said earlier, Terry's H9 build log is a great reference and I used it extensively in my build. When I was at your point in trying to get my engine to run, there are some comments from Swede in Terry's build log that for me were spot on. I'm sure you've read them, but his recommendations on carbs, carb setting, starting and oil management might be worth a revisit when you switch the carb. I think you are on the edge winning the battle.

John

 

[Jon James]

Are you sure your fuel tank and crankcase are ventilated? The crankcase is best ventilated thru the scavenger pump with a small hole in the oil tank cap.

Yes Terry. The crankcase is vented through the front of the crankshaft, and I verified it is open. For now, the scavenge is running open to a collection jar

Jon

 

[Jon James]

Jon, Like you said earlier, Terry's H9 build log is a great reference and I used it extensively in my build. When I was at your point in trying to get my engine to run, there are some comments from Swede in Terry's build log that for me were spot on. I'm sure you've read them, but his recommendations on carbs, carb setting, starting and oil management might be worth a revisit when you switch the carb. I think you are on the edge winning the battle.

John

Thanks John. I'll go back and review Terry's build again.
Jon

 

[Jon James]

Jon, what fuel are you using? Lee's engine will run with the Perry 4600 carb. I'm not a big fan of Coleman fuel and last check on price looks like it is getting too expensive. My first go to fuel is 100LL av-gas if it is available in your area. I'm lazy and run my RC aircraft fuel which is E-85 mixed with Klotz oil at 32:1 (did I mention I was too lazy to mix fuel for the little engines so just use my regular RC mix). I have also done some running on the pre-mix sold for the chain saws and trimmers. I prefer the 40:1 mix and the best place so far has been TSC.

https://www.tractorsupply.com/tsc/product/trufuel-40:1-pre-mixed-fuel-32-oz?cm_vc=-10005
If you use the av-gas add one of the 1 gallon 2 cycle mixes to a gallon. Most brands are now using 50:1 which is fine. As for the carburetor, remember we are dealing with an alcohol (which is 3 times more dense than gasoline) design. I have not had the time to try and figure out what needle tapper would better suit the gasoline best but the needle setting will definitely need to be much leaner than what is stated for the Methanol fuel the carb was originally designed for. 40 or 50:1 will give you good top end lube and I'll guarantee it will not effect the operation or performance of any of our model gas engines. The Traxxas 4033 carb should work just fine too. It is almost impossible to put too small a carb on an engine and if you did, all it would do is limit the top end for speed. I believe the Perry 4600 is the same bore as the Super Tiger .60 size carb the guys were using when it was available. It will be good to know if the smaller Traxxas carb works better than the Perry 4600. Glad to see you are making good progress, keep it going.

Roy,
I have used AV100ll, regular pump gas and camp fuel. All with about the same result. The plugs that actually show ignition are usually black and sooty. The plugs that don't make ignition do show signs of fuel on them. I have the feeling I am not getting atomization of the fuel.
I made your "open" distributor design. I can clearly see the rotor and contacts and the spark from the rotor to the studs in the cap. As you said, nowhere else for to the spark to go. This also leads me to suspect carb..
Thanks again for all of your help.
Jon

 

[Jon James]

Steve is correct on the plug gap of .015" and yes my CDI functions different than the old Kettering system. I have talked with Lee about some of the issues encountered with the distributor set up. First, we do not need the brass tower contacts protruding down the inside of the cap. This leads to sparks jumping down to the base of the distributor sometimes. Second, the rotor contact is way too wide. It only needs to be a strip about the width of the brass contact in the towers. If you can't get the spark through the distributor, the engine will never run smoothly. I have worked on several of these engines and my last test is with my little doughnut spark tester between the end of the spark plug wire and the spark plug. Turning the engine over slowly by hand and moving the tester from plug to plug in the firing order you should get a spark through the tester. I normally set the gap in the tester at no more than .010- .015. Once the spark gets through the tester it means the distributor is good to go. One more thing that can help. The CDI will function on 4.2 volts so you may have better luck with only 3 cells. This will reduce the output of the CDI and normally it will have much less tendency to jump a spark places it shouldn't. Lots of good advice from members and I see they have had many of the same problems I have dealt with in the past.

Roy,
What should the clearance be between the Hall sensor and the magnets on your ignition?
Thanks,
Jon

 

[stevehuckss396]

Roy can chime in here if I'm wrong but I think it .040

 

[Jon James]

Roy can chime in here if I'm wrong but I think it .040

Thanks Steve, that sounds about right.
Jon

 

[rsholl]

Hi Jon,
Steve is correct on the .040" gap. Now that we ship the hall sensor in the plastic D-tube, the air gap is pretty much the thickness of the tube so the magnet would need to be very close. BTW, the hall sensor can be removed from the D-tube and oriented 180 degrees from the way my wife installs them. Just hold the D-tube and pull gently on the wire and the little wedge and sensor will come out of the tube. Since adding voltage clamping circuitry to my CDI and having the hall sensor mounted in the plastic D-tube, we have all but eliminated hall sensor failures.

Bottom line is, if the LED on the CDI unit comes on and goes off , the hall sensor is seeing the magnet. Speed is not an issue, if it works at slow hand rotation speed it will still work at max rpm.

 

[Jon James]

Hi Jon,
Steve is correct on the .040" gap. Now that we ship the hall sensor in the plastic D-tube, the air gap is pretty much the thickness of the tube so the magnet would need to be very close. BTW, the hall sensor can be removed from the D-tube and oriented 180 degrees from the way my wife installs them. Just hold the D-tube and pull gently on the wire and the little wedge and sensor will come out of the tube. Since adding voltage clamping circuitry to my CDI and having the hall sensor mounted in the plastic D-tube, we have all but eliminated hall sensor failures.

Bottom line is, if the LED on the CDI unit comes on and goes off , the hall sensor is seeing the magnet. Speed is not an issue, if it works at slow hand rotation speed it will still work at max rpm.

Thanks, Roy.