Sport moped exhaust on 66cc (Build thread)

[Street Ryderz]

So that would mean, if I do get the pipes out, it would make more torque? Thats what I understand from what you said.

I'd also loose some top end, right?

A good pipe help's alot in allowing the engine to breath properly,along with proper porting and areas to match it and your carb.The main thing is the volume being pumped by our engines is very small/restricted so matching the flow through it to the pumping efficaintcy is the best you can get,then with a good pipe and port timmings that match, the pipes charge amplify's the out put for that last bit of pull.

 

[JerboaJohn]

there is someone who had that scooter pipe and it works really well,, gains across the board low and top end. but if you go woth it, you'll need to rejet 1 or 2 sizes bigger than stock, but that's a baseline to get close to a good tune

 

[Vikingimike01]

Oh, okay, thank you. I'd need a 75-80 jet than, right? I also have sanded the cylinder a millimeter, and have a B7HS. I guess that would just help then.

 

[JerboaJohn]

80 would be really rich unless you have big ports and great pipe. 70 is stock. so if you can get 71 2 3 4 5,,, you'll be closer. jets are cheap from BMW

 

[Vikingimike01]

Oh, I can only get 60,65,70,75,80... in 5 increments. I have a 70, and will try the 75 then. And my ports are bigger than usual since I widened them as well. Just a tiny bit.

 

[JerboaJohn]

it'll have more oomph, esp freeing up those nonsense inside the pipe. louder too tho haha

 

[Vikingimike01]

I'm mostly OK with the loudness. But not too loud I hope!

I'll do that today, or on monday. After, I'll probably buy an 50cc scooter exhaust, and try to fit it.

Other thing I'll do, is see the piston skirt at the intake side, and if its flat (Not cut out, like here:

I'll probably get a milimeter or two off. Was also thinking of changing the timing, to like 20-15 before TDC (Advanced) I was watching 2STROKE STUFFING and he had a pipe like that scooter pipe, as well as the porting. I'll not do much porting other than widening, wich I alredy did, so yeah, no porting.

 

[JerboaJohn]

i did the piston mod to my 48cc. opening the port fully at TDC, but tho it really woke the engine up, i lost bottom end bcs the intake duration was too long then. I cut abt 6mm :-(

 

[Vikingimike01]

Yes, I know it was going to get rid of a bit of a bottom end, wich I kinda dislike. I just cleaned my carb out after the winter, was full of gas for 4 months before being ran. I had some overhanging metal pieces in the intake manifold (in the inside) that I broke off. I was only going to take off a millimeter or two only from the piston though.

Did you try widening your ports? If yes, how did that go?

I'm going to look into how to modify ignition timing.


I was also thinking about buying a reed kit, and cutting the piston hole out myself. Not sure yet, because theres not much space left on my frame for the carb, not even the air filter* fits

 

[JerboaJohn]

no I didn't widen ports, just smooth out the passages. long offset intake helped boost the low end and plenty room for filter.
here is Jaguar's torque pipe if you can weld. www.dragonfly75.com/motorbike/torquepipe.html
I have a Voodoo pipe and it's good for me bcs of the long header and I don't rev out past 5000.