Expansion pipe good or scam?

[Street Ryderz]

Man I've been playing with pipes on 2t's for just over 40 years now and I'll agree that the pipes marketed for these engines are not the greatest but still are better than stock exhaust even if just for improved flow and less heat.Jag's statement above though is totally whacked 6-9" of header has a huge effect on the topend and will reduce the rpm there!A pipe is designed to work at a given rpm with the port timing and when max rpm is reached within those parameters that's all she wrote,when the wave speed and port timing no longer align trying to over rev it will just be short circuited/running lean and damage the engine.There is also a huge loss of power that usually won't allow any further increase of rpm if you look at any pipe dyno sheet right after the peak it will fall off quickly and make way less power.

 

[Vikingimike01]

In Jenning's book, it says, if you fiddle with the header lenght, it will take/add to the powerband, the same it takes/adds from the other end. So if you have a powerband of 4000-6000, increase it 1k, the lower number will increase as well, so you'll have 5000-7000RPM.

 

[Spare_Parts]

Jag needs to catch up with what's been going on with these engines. Needs to stop preaching the old tech.

 

[Street Ryderz]

I have two video's here the first is a stock engine and speed carb on a board tracker build I did last year it uses 10/40 gearing and the bertha pipe witch was made and marketed for these engines,that bike hits 50 and pulls great!The next is just the shop bike witch my son mostly rides it is also stock engine,stock nt carb,stock gearing and the mz 65 pipe stock this bike is also capable of 50 mind you it's screaming over 11k but it also pulls great and accelerates up very steep grades as you can see in the video.

 

[FurryOnTheInside]

I think Jaguar 's comment was about adding extra length to the header of the stock muffler that came with the kit.

But if I could weld, I would weld something other than the stock muffler.

 

[Vikingimike01]

Well, I can kinda weld. Trust me, you'd weld the stock muffler first, then try other stuff. I'd weld my own exhaust as well, but I'm fine with fitting a premade expansion pipe for a scooter.

 

[Greg58]

A lot of what has been said in this thread holds true for the pipes I’ve built, the best I’ve managed has a 16” head pipe and helps a lot for low end power. I wasn’t after top end but mine didn’t lose any.