Motobecane 50v stock exhaust mod question

I am wanting to gain a tad more power with my stock exhaust. I removed my exhaust to check/clean my exhaust but suprisingly it looks pretty clean except some carbon buildup on inside walls of exhaust. Baffles and outlet tube looks good, I will clean anyways. It is recommended to make a blanking plate on the end of the exhaust and drill until no more performance is gained. That seems to me like it changes the flow of exhaust, and I would think change performance of the pipe? When a size is determined, the inner baffles need to be drilled out, then a tube with proper id as blanking plate test made and bent to fit into baffles and then out the ball end? (which probably needs to be drilled to accept tube) I have stock 50v with delloroto 14.12 60jet, Is this modification usually advised to change jet? I could have tried all before asking the question but appreciate everyones opinion here and like to get them before jumping in, especially when time is on my time(winter)

http://mabecanemobylette.freeforums.org/blunderbuss-exhause-modification-t1394.html

Re: Motobecane 50v stock exhaust mod question

i ussually drill six small holes on the underbelly of the pipe down each side of the seam, it spits most of the noise at the ground.

Re: Motobecane 50v stock exhaust mod question

Now that you mention it, I could just cut the entire pipe off and run just the header. Six holes is amateur hour. No one really cares about noise anyways...lol

Re: Motobecane 50v stock exhaust mod question

Probably Fred /

Kevin Centers Wrote:

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> Now that you mention it, I could just cut the

> entire pipe off and run just the header. Six holes

> is amateur hour. No one really cares about noise

> anyways...lol

No not really

A 2 stroke needs a expansion chamber and if it can't have that it at least needs some back pressure

Re: Motobecane 50v stock exhaust mod question

dude, use a 15mm SHA.

Re: Motobecane 50v stock exhaust mod question

If noise = performance then folks would just remove the exhause completely.

You need containment for the spent gasses and not just free flow, without containment the exhause gases would exit and drag along the fresh cooled charge with it and not allow some of the cooler medium to drain the heat from the periphery of the piston crown where the exhause port is - which leads to melty piston and galling or seizing depending on how lean the charge is and how much parasitic heat it is creating.

Stock-ish Mobys you need about 11mm or equivalent cross section area if you are making multiple holes. There is ample size hole in the baffle plate inside the pipe that you dont have to drill the heck out of it.

Re: Motobecane 50v stock exhaust mod question

I thought steve was making a joke but maybe I misunderstood and that really is what he does, thats seems bizarre to me but if it works then great! I was kidding about the open header, I know that is a no no on two stokes.

As far as the exhaust goes, I need to drill out the two transfer holes slightly bigger, and cut out the outlet tube and put a slighly bigger i.d. pipe in? Does the outlet pipe necessarily need to go back through the baffles. That is what impression I was getting from rebels tutorial.

Are the 15mm carbs much better on a stock setup?

Re: Motobecane 50v stock exhaust mod question

I was thinking of doing the following, but I dont know if putting on the shorter pipe will help or hurt performance of the pipe.

Re: Motobecane 50v stock exhaust mod question

Shorter bigger pipe will help with performance. Short pipe means the exhause does not have to travel twice as far through the two baffles before getting to the exit pipe. Have to keep in mind the that the stock pipe was designed for silencing the noise: 74dBA according to their documentation submitted to the governing body in France for regulatory compliance.

Re: Motobecane 50v stock exhaust mod question

That is good information, then I will start with the shorter, bigger pipe before I drill out the other holes. There will be an extra hole in the baffle plate so that in itself adds area to the opening, even though the exhaust will be moving in a different direction. I will let you know how this mod affects my performance. Thanks again for always being up for helping me and answering questions.

Re: Motobecane 50v stock exhaust mod question

Listen to steve sabat

Re: Motobecane 50v stock exhaust mod question

hey Kevin, did you ever make the exhaust mods?

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