[Ruyguy]

The following is the video I am basing myself on.

Unlike the crank in the video , the fcc , on a balancing stand, will drop down on the rod end, so adding weights on the rod to get it to stay in any position ( like in the video ) …
Im guessing the balancing factor is off but on the opposite side than it is in the video? Can anyone help me on this?

 

[MrKitty]

The FCC cranks balance factor is off by so much that it's not usable if you add tungsten to balance it out it increases the rotating mass of the engine and makes it kind of sluggish

 

[Ruyguy]

The FCC cranks balance factor is off by so much that it's not usable if you add tungsten to balance it out it increases the rotating mass of the engine and makes it kind of sluggish

Oh man that sucks, is this something you know from personal experience?

 

[MrKitty]

I tried to fix it three different ways

By adding tungsten only.
By adding some tungsten and then adding the rest of it in steel slugs in the flywheel.

The best results I had was I drilled out the one side and I had to drill out a lot and add a little bit of tungsten to get the desired 45% balance Factor the problem with this is I had to hog out so much that the crank lost its stuffer like ability what I mean by that is it no longer filled the entire void of the crankcase.

Moving along to problem two the FCC blocks a lot of the feed ramp area interrupting the flow of the engine.

And problem three the fuel charge has to be squeezed in between the connecting rod and the crank halves.

I have built about 12 of these engines over the years all different ways I speak from personal experience

 

[Atvrunner2]

Yeah, I have never bothered to balance the cranks on these chinese tool based engines.

 

[Ruyguy]

I tried to fix it three different ways

By adding tungsten only.
By adding some tungsten and then adding the rest of it in steel slugs in the flywheel.

The best results I had was I drilled out the one side and I had to drill out a lot and add a little bit of tungsten to get the desired 45% balance Factor the problem with this is I had to hog out so much that the crank lost its stuffer like ability what I mean by that is it no longer filled the entire void of the crankcase.

Moving along to problem two the FCC blocks a lot of the feed ramp area interrupting the flow of the engine.

And problem three the fuel charge has to be squeezed in between the connecting rod and the crank halves.

I have built about 12 of these engines over the years all different ways I speak from personal experience

Nice , and by the way no disrespect when i asked if it was from experience, that’s exactly why i asked so that id get that detailed explanation you gave me . That said.
First i thought we were aiming for 55 not 45,

2 i hogged out a pArt of the case in the feeding ramp.. basically widened the wholes case in the corners especially, im hoping to give more space for the charge to go past.
3 i guess you just dont use a fcc in a crank anymore?

 

[Ruyguy]

cuz i have a half crank 12mm lying around here if your saying the fcc is just all around bad anyway ill still probably try it with other mods and see what it does .. i wanna try directing flow between the 2 crank halves by flipping an ada style reed block 90°

 

[Atvrunner2]

A FFC is great for a low end engine, one that won't see high RPMs much. I have a half moon crank that had been lightened. In the middle there is 2-3mm of the crank machined down, much more open in the middle, that might work well for FFC.
I built a mild 44mm (1 pc) with FFC to sell. I broke it in on a bench was smooth but I didnt rev it up high. The guy that bought said it was a ripper and decently smooth. It was a mild port/blueprint job on the case and cylinder base. Rocket key (advanced), reed stopper modded, squish around 0.048", and HP clutch springs. Flywheel and clutch left stock otherwise.

 

[MrKitty]

Hey I am all up for people trying new things just because my recipe was bad doesn't mean yours is going to be so give it a shot let us know what you did and how you got there.

45% balance Factor seems to be okay I agree with you 55% is the aim point anywhere between 45 and 55 is going to be the sweet spot for these engines sometimes getting them to 55 is just too much work.

 

[Ruyguy]

Yeah, I have never bothered to balance the cranks on these chinese tool based engines.

Did the unbalanced-ness of the fcc basically rob the motor of any power gains the other mods give it? Ive been blocked and have not advanced the build what so ever since making this post , i feel kinda stuck and like ive done att this for nothing,
Like i could have put in the same work with better results with a ktm 50 cline engine..
maybe the fcc is in in 44 since they rev less.
Anyway ill see what i can do. What do you guys think,
1 try balancing
2 just out the damn thing in
3 use the half moon instead

 

[Ruyguy]

Hey I am all up for people trying new things just because my recipe was bad doesn't mean yours is going to be so give it a shot let us know what you did and how you got there.

45% balance Factor seems to be okay I agree with you 55% is the aim point anywhere between 45 and 55 is going to be the sweet spot for these engines sometimes getting them to 55 is just too much work.

What i was thinking would MAYBE work was drill out holes in crank and fill with something light but resistant like an epoxy . Jb weld maybe. As long as it doesnt pop out i dont see why not..
i lowkey found a fully build cag motor online
70cc
Balanced crank
Aluminum billet case with the entry on top
250 euro

 

[MrKitty]

Just put it together and see how it runs no sense in wasting it full send it then build something else or use the parts to build another CAG.

Yes there are a lot of options out there but none as cheap as CAG engines where you can get a fresh one for under 75$

 

[Atvrunner2]

Did the unbalanced-ness of the fcc basically rob the motor of any power gains the other mods give it? Ive been blocked and have not advanced the build what so ever since making this post , i feel kinda stuck and like ive done att this for nothing,
Like i could have put in the same work with better results with a ktm 50 cline engine..
maybe the fcc is in in 44 since they rev less.
Anyway ill see what i can do. What do you guys think,
1 try balancing
2 just out the damn thing in
3 use the half moon instead

I haven't had too much problems with the full circle cranks, really good for low end torque but not high RPM. I would definitely keep on your course and try it. Like kitty said, it's the cheapest engines out there to mess with. Epoxy would be a great idea or even JB Weld, should be lighter than the crank.

 

[Ruyguy]

I haven't had too much problems with the full circle cranks, really good for low end torque but not high RPM. I would definitely keep on your course and try it. Like kitty said, it's the cheapest engines out there to mess with. Epoxy would be a great idea or even JB Weld, should be lighter than the crank.

I almost wish you hadnt said that , but i dont obviously haha just means now i gotta try it hahahaha

 

[MrKitty]

You should put it together with the mods you have done and see how it runs maybe bump the compression and run RC fuel

 

[Ruyguy]

You should put it together with the mods you have done and see how it runs maybe bump the compression and run RC fuel

You mean like with the unbalanced crank?

 

[MrKitty]

Yes try it out and see if the stock crank or the unbalanced fc crank which one makes the most power for you

 

[Ruyguy]

Did this a while ago , havent had much time to do anything lately,
But if my math is correct id have an initial balance factor of 7% lmao,
These are my specs

 

[Ruyguy]

 

[MrKitty]

Yea that's the problem with the FCC if you can get the BF more around 35% ( 50% is better ) it will provide better horsepower in the higher RPM band I would go ahead and drill it and try to fill it with JB weld