help please

[krankie frankie]

I have finally gotten my version of Brian Rupnow's hit/miss i.c. engine assembled. It starts well enough but immediately goes into a astounding over speed condition which requires that I snatch the wire off the battery before bad things happen. I am using automotive type ignition and have tried both a small bore and a larger bore carb with the same result. Any ideas on how to correct this problem would be greatly appreciated.

frankie

 

[stevehuckss396]

Try to PM Brian and see if he can help. Sounds like the mechanism that makes it miss may need to be fine tuned.

 

[Cogsy]

Definitely sounds like it's not going into 'miss' mode. Have you checked if the lever will engage the pushrod 'catch' and hold the exhaust valve open? How about the adjuster screw mechanism for the flyballs? - I had too long a spring on mine at one point and it got bound up so the balls couldn't fly out enough to engage the pushrod catch.

With the engine stopped and the exhaust valve closed, manually extend the balls to their full extent and then you can see if your lever is coming up high enough to catch the pushrod and hold the valve open. If that's ok then turn the engine till the valve is fully open and again extend the balls to see if the lever is in the correct position to engage the catch.

If all that is ok then at a guess I'd have to say the flyballs are binding/tight and aren't extending properly when it's running.

Hope some of this helps!

 

[krankie frankie]

According to the posts that Brian put up it needs to run as a four cycle engine before the governor is put on. I have not gotten to that stage of the game. It starts and goes directly to a gazillon rpm. If I turn the needle valve down then it will stop. I think tomorrow I will do the "V" mod to the cylinder head and see what happens. If anyone else has an idea please post it and thanks to those that already have.

frankie

 

[Cogsy]

Not sure I ran mine overly long before fitting the hit and miss mechanism, just enough to make sure it was going to run at all. The head modification won't solve your issue as your engine is running far too well already - that's causing the overspeed. As designed, the carb is like having a wide open throttle for use with the governor.

If you want to run it un-governed then you will either need to fit a throttle (I briefly had an RC throttled carb on mine for testing) or you could try running the engine at a really rich needle setting to try and 'bog it down'.

Realistically, if it runs that well that it wants to overspeed then you can just go ahead and fit the hit and miss mechanism and it should function perfectly.

 

[collbee]

Could timing play a part as well ??

 

[Brian Rupnow]

Okay--I just seen your post. Help is at hand. By the very nature of the way a hit and miss engine carburetor works, your engine is doing exactly what it is supposed to. Congratulations!! You have a runner!!! Now---Before it self destructs---the governor weights are supposed to fly out at any rpm much over 250, and through the train of levers and pivots, the "sprag" lever should engage the exhaust valve pushrod and hold the exhaust valve open so the engine will not make any compression, and so consequently the engine doesn't fire. As the engine slows down, the spring in the governor mechanism will return the balls to their "at rest" position, and the "sprag" lever will disengage and let the engine make compression again and fire, repeating the whole cycle. If you live in north America, email me at [email protected] and send me your real phone number. I will call and talk you through it.---If you want plans for a carb with throttle, email me.Brian