Hello, I realise this is a thread resurrection but I wanted to post my thoughts on the Marving (AMACAL) exhaust. I couldn't find much when I searched.
My bike is a 1999 Yamaha XT600. I needed to replace an old Leo Vince X3 that was too loud for me, and past its best.
I considered the Arrow and the Marving. There seems to be more people who have the Arrow but the 'not for road use' element put me off. Also many reviewers state that it is quite loud.
I ordered the exhaust from wemoto.com on Monday and it arrived on Tuesday. The cost was £175 or so and delivery was free on UK mainland.
In the box
In the box was the exhaust all nicely bubble wrapped and a Marving logo plate that you can stick on if you want. There is a clamp for securing the exhaust to the downpipes. There are no fitting instructions - not that any are really necessary. I was really pleased with the quality of construction. Nice welds, nice chrome and an aluminium plate for the visible part of the can. Better than I expected. There are no bolts in the box so I had to head to a well known hardware shop to pick up a couple of M10 bolts and an M8 bolt, plus washers.
The Marving is a single piece whereas the Leo Vince that it was replacing was 2 piece. This made maneuvering the exhaust onto the downpipes a bit more fiddly, but not a problem. I had the Yamaha graphite gasket, but the inner diameter of the Marving pipe didn't seem designed for it. I just used some exhaust paste.
The Marving has a captive nut for attaching the pipe to the frame of the bike just behind where it attaches to the downpipe. It has 2 mounts for attaching to the frame at the can. These allow for horizontal adjustment but not vertical. After a couple of trial fits it was clear to me that these mounts would not quite fit the frame on my bike, so I had to file each one out to allow for a little vertical adjustment, only by a couple of mm. After that it fitted well.
Thankfully the bike is now quieter than it was with the Leo Vince (I never had the sound deadening thing for it). I can't compare it directly with the stock exhaust because the bike had the LV on when I bought it. However I also own a TT250 with a stock exhaust, and the Marving has a more heavier tone that this and a bit louder.
On hard acceleration you still get a good roar, on shutting the throttle I still get some audible burble (and the odd pop, my bike may be running a bit lean). On coasting and constant throttle the noise is not intrusive.
I can't tell a difference. However now that it doesn't deafen me and all around, I am more prepared to give it the full beans. So in that respect the bike is a lot faster
One other thing I noticed is the frame on the rear of the bike now 'seems' a bit stiffer. It must be due to the new exhaust being a single piece. The evidence is totally empirical: I have a top box on my bike with a chain in it. I used to hear the chain bouncing around all of the time, now not so much.
It is a bit smaller than the LV in length and diameter (it is round, not oval). You can see more of the rear wheel from the side now, which is better aesthetically.
All in all its a significant cost for the value of the bike but has been worth it for me, as I'll use the bike more.