Akrapovich system no good on road bikes long term
This was posted on a 690smc specific thread but it applies to all single cylinder 4 stroke bikes so I've decided to give it a life of its own.
First up I must say that the Akrapovich system is sold as "Race Only" and therefore, on a race track, is unlikely to ever reach the milage I reached on the street. Be warned: Akrapovich do not represent this system as a street system.
In New Zealand though, we can fit any muffler/exhaust as long as it's quiet enough and, with the DB Killer fitted, it was.
I've owned a few KTM's now: 640SM, 950SM and 690SMC. I've had Akrapovich Titanium systems fitted to all. On the 950 I had no issues even at 35,000km when I sold the bike. Obviously the smooth Vee Twin was less punishing to the muffler.
HOWEVER, on the big singles, and I suspect all 4 stroke singles, the Akrapovich titanium system is NOT GOOD FOR LONG TERM ROAD USE. The issue is longevity and vibrations.
On my 640SM, the end cap rattled out of it's rivets within 7-10,000 kilometres and the rivet holes in the body of the muffler actually shattered and broke pieces of metal out of the muffler. I ground these smooth and redrilled new holes in the end cap and muffler in different places so I could refit the muffler to the bike; that lasted perhaps another 5,000km (can't guarantee the numbers but I gave up on the Akra long before I sold the bike and fitted another system).
The modified muffler ended up wrecked as it actually split apart along it's length.
I thought the 690SMC would be much better given that it vibrates far less and in a way I was correct; it lasted at least twice as long but in the end the exact same problem has occured. These are very expensive kits and a complete system as I have is around NZ$4,500 retail. That's double the price of say a pretty good FMF (not 4.1). My Akra on the 690SMC has fractured the rivet holes just like on the 640 and as these are now open intead of holes; I'd have to again grind them to smooth curves and drill new rivet holes elsewhere. The problem is that this system is the one with a carbon end cap and the bottom of that end cap has shattered with the Ti rivet holes on the body of the muffler. To fix it I'd have to get a new end cap and grind/redrill the body again and frankly, I would not expect many more km's from it anyway.
Note: I was using the DB Killer in both bikes at first but found that this actually made things worse with more back pressure. Yes, I did repack the muffler as it blew the fibregalss out.
My advice to anyone looking for an aftermarket system for a road going single cyclinder 4 stroke would be to avoid the Akrapovich Titanium systems. They really ARE Race Only and you'll not be doing yourself any favours buying them in the long run. I'd also be dubious about the long term life expectancy of a carbon muffler due to the vibrations and exhaust pressure of a big single.
I would recommend a good stainless steel or cheaper to replace alloy muffler for these bikes.
Anyone had similar experiences or who has done as many or more kilometres/miles on a muffler they can recommend?
Last edited by idleidolidyll; 10-20-2011 at 02:29 AM.
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