Engine Question

[Ericke1]

I recently returned my Ofna Force .26 to Ofna for repair since the connecting rod melted (apparently the engine was too hot). Anyway, Ofna charged me 50 bucks to rebuild it, with a new piston, sleeve and connecting rod because they said this was not under warranty. I paid.

I got the engine back yesterday and I noticed something odd. On one end of the engine you can see the connecting rod mounted to the sleeve. On the other side of the engine when I turn the long rod where you mount the clutch and gear on (dont know what you call that part-basically its the rod on which the gear is mounted with the clutch) it turns smoothly but when the connecting rod (on the other end the connecting rod makes a circle when you turn it) completes half a turning diameter it gets very hard to turn the rod and after a lot of force it becomes easy to turn the rod again. So basically the connecting rod makes a half circle smoothly and when it reaches the other half it becomes hard to complete its rotation.

Is this normal? Am I making too much of it or should I send it back to OFNA?

Never mind, I called OFNA and they said this is called PINCH and it will go away with the engine break in process. I felt silly for asking.

 

[Gimpy00Wang]

Since it's a new piston/sleeve, you'll need to break it in again. It is normal to have additional resistance with a new piston/sleeve.

- Chris

 

[mikeburgin]

Now its been rebuilt it like a new engine, you'll need to run it in nice and rich so you impregnate everything in there with oil, a proper run in gives you alot longer engine life, use castor oil fuel not synth, these engines are desinged to run on castor, and preferably a high grade fuel not cheap stuff
this is the method i use
1) start the motor in the car with no clutch on it, it eliminates any hassles with a clutch the engages early, I run a oil rich mix on the bench at a little over idle for 2 tanks,
I stop the engine and put the clutch on after the first 2 tanks,

2) take your car to the track and run another 4-8 tanks through with it tuned very rich you want to see plenty of smoke and you dont want the motor to rev full revs but you do want to give it plenty of throttle, so give the gar burst of full throttle and them nothing

3)now you can lean the car out abit but not alot and run another 4 tanks of fuel through it.............................engine should be getting pretty well run in by now but should still feel tight

4)lean your car out for full performance an then back the main needle back and 1/8th of a turn just to ensure that your not running to lean, if you think its still a little hot back it a quater of a turn, should ensure you dont cook it again

 

[robriguez]

That PINCH as they call it is the piston reaching the top of the sleeve and compressing the air in the fuel chamber. That compression (along with the glow plug) is what enables our little engines to turn a bit of nitro fuel into power. This is normal for it to be tigher than it was before as it is basically almost a new engine again.

Just make sure to baby it for a bit and dont go over 1/4 throttle in the beginning never running it more than a few min before shutting it down, letting it cool a bit then starting again. After about the 4th tank of gas you can start to open her up a bit but still take it easy. The more careful you are not to overheat the engine at very high revs in the beginning will keep your engine running stronger for longer in the end