Hey guys,

I will need to fab a custom exhaust to for my engine swap project so I was wondering if anybody has recommendations on the best header diameter. I am not looking for max HP but rather a slight overall improvement if possible.

I see that both LeoVince and Arrow sell full exhaust systems so I guess these would be a good starting point. Does anybody know the inside diameter of the 2 header pipes as well as the merging pipe?

Cheers,
Lukas

ttt

loosen the bolts and get a micrometer and measure them. if you're doing a "custom " deal then these are skills and tools you already posess.

I don't get it Mark. Yes I have a micrometer, and yes I do know how to use it. What exactly are you suggesting that I measure, though?

Do you already have your engine for the swap?
Can't you measure the stock exhaust for a baseline?

I don't have a micrometer or I would help you out and at least get the outside diameter of the stock exhaust at various points. Maybe I'll grab one tomorrow.

Hi Shatrat,

I bought an engine on Ebay a month ago but due to some shipping problems it still hasn't arrived. Not sure if the seller is going to include the header or not.

I appreciate your offer to measure the stocker, but I don't think this will be the solution. While it's diameter wil definitely give me a baseline I still won't know how much bigger the Leo and Arrow are. Could be 1mm or 5....

I guess I will have to keep my eyes open on the main board, and when somebody buys a new header ask him to measure it before installing.

Thanks again for the help.

Lukas

Stock header down-tubes outer diameter: ~34.5 mm. Inner diameter: ~32.5 mm.
Muzzy header OD: 1.5" (38.1 mm) ID: ~36 mm
Stock header pipes protrude 12 mm inside the gasket seat, but could be 15 mm or more to be closer to edge of exhaust port outlets.
There's room for header pipes of up to near 40 mm OD, but an ID of about 34 mm would be a pretty good size for the exhaust port outlets which I smoothed out.
Stock header collector pipe is 42 mm OD / 40 mm ID. My Muzzy header's collector is 2" (50.8 mm) OD, and about 48.8 mm ID.
Arrow's header has a nice design with the down-pipes' OD starting at close to stock OD, tapering to a slightly larger OD almost halfway down.
Its collector size is matched to stock 40 mm ID, as its slip-on fits stock header collector.
My Muzzy header is the only one that has a larger collector on which stock or aftermarket mufflers don't fit.

Pics show stock header, Arrow header, before & after exhaust port outlet:

http://img246.imageshack.us/img246/3929/stockheader.jpg (http://img246.imageshack.us/i/stockheader.jpg/)
http://img180.imageshack.us/img180/8313/arrowq.jpg (http://img180.imageshack.us/i/arrowq.jpg/)
http://img508.imageshack.us/img508/9149/exhaustport014.jpg (http://img508.imageshack.us/i/exhaustport014.jpg/)
http://img23.imageshack.us/img23/4876/exhaustport021.jpg (http://img23.imageshack.us/i/exhaustport021.jpg/)

Invader, you rock man! Exactly the kind of information I was looking for, thanks a bunch for digging it up.

I like the Arrow design, will probably go with increasing diameter like that as well. How did your bike feel after the Muzzy install, any loss of torque due to lower exhaust velocities? 10% larger diameter is quite a bit.

Thanks,
Lukas

You're welcome, Lukas... I figured you missed my edited post #7, so I deleted it and just reposted it again. :thumb:
I never even tried or heard my new Versys last year with stock exhaust, PAIR valve and sub-throttle plates, among other things, so I still have the entire unused stock exhaust system for sale... It does run real good and strong, especially with ignition timing advanced 5 degrees, larger inlets on heat insulated airbox, smooth-matched TB flanges/intake port inlets, properly adjusted TPS, 6" vacuum hose (1/8" ~ 3 mm ID) coupling both TB synch fittings... The Muzzy silencer was too loud even with added baffle plate, so I cut it off at the elbow and welded a 2" in/out 4" OD round 14" Magnaflow (automotive) brushed stainless steel silencer with straight-flow 2-1/2" ID core, and welded on a stainless steel Yoshimura TEC-SD2 1-7/16" ID 'low volume insert'. It sounds just great, smooth and deep. I couldn't ask for better. :clap:

http://img22.imageshack.us/img22/3574/exh006.jpg (http://img22.imageshack.us/i/exh006.jpg/)
http://img22.imageshack.us/img22/9742/exhaust010.jpg (http://img22.imageshack.us/i/exhaust010.jpg/)

Nice information, been trying to get somebody to measure headers for over a month on the BRP forum :forgetit:

Before seeing this thread I've decided to go with 38mm OD (1.5") tapering to 44.45mm (1.75") OD into a 2" collector.

I'm building a pretty serious engine before I get bashed for going too big :thumb: