Custom pipe experience? Cut Weld Hack Benelli G2 / A35 Pipe

This is my first attempt at cutting and welding a pipe together and looking for your experience and advice on next steps. Its a Moto Guzzi Robin (Benelli G2) - I grabbed this cheapo Tomos Techno Circuit Pipe locally for $30.

It points right up to the cylinder with no modifications but is obviously hanging too low on the bike.

So this is the original header cut off the original exhaust. I was thinking I could find or make a 90 degree elbow but would that be a problem for performance?

My other thought was to try to heat and bend this one and have it meet back up with the pipe closer to the next bend:

You see how far off the original header is here:

Re: Custom pipe experience? Cut Weld Hack Benelli G2 / A35 Pipe

Brandon Weiss (Detective brandon to you) /

Referencing the 3rd picture, cut off the stock header at a sharper angle to better interface with where the pipes header is, and then cut a piece from scrap to bridge the gap. Take your time fine tuning the fit of the pieces with files. A little goes a long way when it comes to filing for a snug fit.

Make sure you have a good solution for the rear mount before you commit though.

Re: Custom pipe experience? Cut Weld Hack Benelli G2 / A35 Pipe

If you can bend it without kinking it, that's what I'd do.

The wave will follow any curve, no matter how tight, but doesn't like kinks or square corners.

My circuit pipe on my Cimatti hung low on the left side and would scrape around corners. Mostly because fat pipe, and 16" wheels.

I used a piece of wood as a lever and wedged it between the header and the rear cone (with the pipe off the bike,) and slooowly leveraged it to twist the rear cone up. Raised it a full inch.

Re: Custom pipe experience? Cut Weld Hack Benelli G2 / A35 Pipe

Header length changes pipe performance, keep that in mind

Heat and bend is usually the way to go

Re: Custom pipe experience? Cut Weld Hack Benelli G2 / A35 Pipe

Header length equals 400rpm per inch, so it’s not gonna change much.

Personally, I have a metal library here with junk steel tubing with various bends that I can harvest when needed. Handlebars are the best for header bends. Chop out a section and add it in. Remember, only the inside of the pipe is important. Make the transitions seamless inside. As well, after welding be sure to heavily hose out the pipe so you don’t get a lil metal chip surprise into your cylinder.

I generally tack weld things together while on the bike with leather stuffed in the ex port to stop any debris getting in there. You gotta make sure any areas with gas are covered and masked off from sparks with leather pieces or sheet metal in order to not kill yourself. Then once things are tacked you pull it off the bike and do finish welding. (edited)

Re: Custom pipe experience? Cut Weld Hack Benelli G2 / A35 Pipe

And don’t burn thru, it’s super easy to do if you’re doing mig or flux core. I do many small tacks first then weld over them, or if I run a bead from the start I run a low power setting in order to not punch holes. But the multiple tacks works good to stop punching thru the pipe

Re: Custom pipe experience? Cut Weld Hack Benelli G2 / A35 Pipe

Okay I got the pipe all fabrication and installed.

This added about 5 mph to the top end, so much better so far. I am at about 32 mph with a new set of rings and 14:12 carb.

I’m thinking my next move is a bigger intake and carb...

Since this bike is fairly stock and not much options for the top end what would be my next move ? 15:15 with a matching intake ?

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