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Hercules Help

denby

Registered
I am having trouble timing my 1.5 hp Hercules. The valve timing is correct but im having trouble with the spark. It has a trip wico and when I adjust the striker to what I think is the correct position the cam wont let the pushrod come back far enough to come behind the magneto trip. If I bring the striker back far enough to come behind the trip it becomes to retarded. Can someone with a similar engine please measure the square striker arms length on their engine please so I can see if that is the problem. I have promised my young son we would look at it in the morning so hoping someone can help tonight. Thanks in advance
 

Andrew Mackey

Moderator
Last Subscription Date
05/14/2017
Re: hercules help

The exhaust valve should open about 20 degrees before BDC, and close at TDC. With the timer set at retard or start (lever raised), the mag should trip at TDC Compression stroke. Using the correct springs on the trip and return are critical. If the magneto magnets are weak, that will also affect trip timing. Is the center post on the mag worn? Both poles should separate from the core at the same time. If they cock when the mag trips, you will not get good spark. There should also be a spring on the exhaust push rod, to make it return fully after openning the exhaust valve. This keeps the pushrod against the cam at al times.
 

denby

Registered
Re: hercules help

The magneto itself works great, no wear. The exhaust valve timing is correct and the return spring for the pushrod is working but it is like there is not enough travel back so the striker can get behind the magneto
 

Kirk Taylor

Registered
Re: hercules help

The magneto itself works great, no wear. The exhaust valve timing is correct and the return spring for the pushrod is working but it is like there is not enough travel back so the striker can get behind the magneto
Is this a new-to-you engine? Has it been like this since you've owned it, or did something happen in the midst that is used to work but now it doesn't? Has any part of the mag trip or bracket been repaired?
If you would, take a couple of measurements.
1) Measure the total travel of the pushrod from fully retracted to fully extended.
2) Remove the trip finger from the bracket, if you can, and measure the distance from the back of the square to the end of the center bolt. I lieu of that, you could carefully measure the distance that the trip finger "compresses" before the mag trips. If you do that, make note of the retard lever position.

If I can remember, I'll take the same measurements on an engine when I get home tonight.

Kirk
 

Kirk Taylor

Registered
Re: hercules help

Is this a new-to-you engine? Has it been like this since you've owned it, or did something happen in the midst that is used to work but now it doesn't? Has any part of the mag trip or bracket been repaired?
If you would, take a couple of measurements.
1) Measure the total travel of the pushrod from fully retracted to fully extended.
2) Remove the trip finger from the bracket, if you can, and measure the distance from the back of the square to the end of the center bolt. I lieu of that, you could carefully measure the distance that the trip finger "compresses" before the mag trips. If you do that, make note of the retard lever position.

If I can remember, I'll take the same measurements on an engine when I get home tonight.

Kirk
I took some measurements this evening:

"Lift" of the pushrod
a) from fully retracted to the end of the trip ramp = 11.9mm (15/32")
b) from the end of the trip ramp to fully extended = 11.1mm (7/16")
c) total lift from fully retracted to fully extended = 23mm (29/32")

Trip finger:
Distance from the back edge of the square to the end of the center bolt = 53.9mm (2 1/8")
"Compression" of the finger while cocking:
Advance lever down = 3.97mm (5/32")
Advance lever up = 5.56mm (7/32")

Just out of curiosity, does the trip finger spring have a flat washer at each end of the spring?

A lot of bizarre things happen to engines during their lifetimes. Things get bent, broken, misplaced, maladjusted, and rearranged. Some are less obvious than others. A photo of your trip, bracket, and pushrod might help to reveal the cause of your troubles.

Kirk
 

denby

Registered
Re: hercules help

I have had the engine for a few years but have only just started to restore it as my 9 year old has taken an interest. it was reasonably complete when I found it but was not a runner. I cant see that any of the trip mechanism has been repaired. I did grind the end of the striker to put a sharper edge on it. I will do those other measurements in the morning. Would you mind measuring the actual length of your striker?
 

Kirk Taylor

Registered
Re: hercules help

I have had the engine for a few years but have only just started to restore it as my 9 year old has taken an interest. it was reasonably complete when I found it but was not a runner. I cant see that any of the trip mechanism has been repaired. I did grind the end of the striker to put a sharper edge on it. I will do those other measurements in the morning. Would you mind measuring the actual length of your striker?
The length of the square part is 57.15 mm (2 1/4") making the total length 111.12 mm (4 3/8"). The length of the square is not critical. Any changes to that are compensated for by adjusting the trip assembly on the pushrod. So, if you would grind, say, 2 mm off of the end of the square, you'd simply move trip ahead by the same amount to return everything to the original setting.
The critical length is that of the center bolt that the spring encloses. The distance from the back of the square to the end of the bolt determines how much the spring gets compressed as the mag is being cocked. If that distance becomes too great, i.e. the center bolt is too short, then the pushrod won't have enough lift to trip the mag before reaching the crest of the cam lobe.

Kirk

---------- Post added at 09:24:09 PM ---------- Previous post was at 08:27:21 PM ----------

I have had the engine for a few years but have only just started to restore it as my 9 year old has taken an interest. it was reasonably complete when I found it but was not a runner. I cant see that any of the trip mechanism has been repaired. I did grind the end of the striker to put a sharper edge on it. I will do those other measurements in the morning. Would you mind measuring the actual length of your striker?
I know you said that you have the exhaust timing set correctly. Double check the cam gear setting. There should be a little cast arrow on the face of the gear. That arrow needs to line up exactly with the keyway in the crankshaft. If the cam gear setting is off, it'll be tough to get the ignition timing set correctly.

Kirk
 

denby

Registered
Re: hercules help

The timing gears were going to be my very next question. I will check my marks tomorow

---------- Post added at 08:22:40 PM ---------- Previous post was at 08:19:13 PM ----------

What is your overall length of your pushrod? I think mine may have been welded where it transitions from square to round which could have changed the length
 

denby

Registered
Re: hercules help

I have just checked the striker spring and centre bolt. The spring on the centre bolt had a washer on each end but also had bits of wire and other washers to shim the spring. Im pretty sure they are not original so when I removed them there was no tension on the spring. Im wondering if the spring is not original or has been weakened
 

Kirk Taylor

Registered
Re: hercules help

what should the free length of the spring on the square striker be?
The free length of the magneto drive spring is 42 mm. At each end of the spring is a 2.4 mm thick flat washer. There is also a 0.74 mm flat washer on one end. The trip assembly that I have in front of me appears to have never been apart, so I have no reason to believe that the three washer are not original.
I have been pondering your problem of not being able to get the mag timing adjusted. Spring length and pushrod length are arbitrary to the timing of the mag. The rise provided by the cam and the compression distance of the drive spring determine whether or not there is enough travel of the trip assembly to load and unload properly. One thing I thought of is this:
On the very bottom of the mag armature is a yoke with a screw through it. This screw slides into the slot on the mag rocker. On the screw there is to be a bushing 7.93 mm (5/16") in diameter, which is the width of the slot in the rocker. If that bushing is missing, there will be a tremendous amount of lost motion between the rocker and the armature. That can cause the very problem you are experiencing.
 
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