Exhaust pipe cracks
Moto Guzzi Quota 1000 and Quota 1100 ES models
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Martin Standing sent me several articles directly related to his Moto Guzzi Quota 1100 ES. I am happy to host his articles. Enjoy!
Cracks in the down pipes and collector box seem to be very common according to what I have read on the internet.
While riding at low speed a strange squeaky noise alerted me that something wasn't quite right with the bike. A quick examination and the source was obvious there were cracks around the balancer pipe between the two down pipes. Interestingly, I had not noticed these when I purchased the bike. If they were there they were certainly much smaller and more inconspicuous. I decided to repair these myself, feeling that I wasn't ready to throw too much money at the Quota yet. On removing the exhaust I noted that there were several cracks on the collector too. The cracks on the collector were interesting and I could not really see a good reason for these, the inlets and the outlet have strengthening gussets (plates), which should reinforce the pipes not only were there cracks in the pipes, but also in the gussets. Offering up the exhaust to the bike again it was obvious that the fit is not perfect and particularly the balancer pipe seems to stress and spring the down pipes, but I have seen worse fitting exhausts. Many years ago, an argument against stainless steel exhausts was that they are more prone to cracking than mild steel. It is generally true, mild steel is more ductile and malleable than stainless, but I have had several stainless systems over the years and have never seen anything quite like this. Whether it is a poor stainless grade choice, vibration, poor fit or a combination; it is extremely likely that a Quota will experience these problems. If you look carefully in the pictures of the down pipes you can see that they were previously repaired with a MIG or perhaps a TIG welder, it's a very tidy job, but is visible.
Photo courtesy of Martin Standing.
Photo courtesy of Martin Standing.
Photo courtesy of Martin Standing.
Photo courtesy of Martin Standing.
Photo courtesy of Martin Standing.
Okay, so what to do about it.
I have read now a couple of times that people have cut the balancer pipe out and welded plates over the holes. The explanation they give is that the expansion and contraction with thermal cycling is the ground for the down pipes cracking problem and this is a very reasonable argument. An option could also be to add reinforcing gussets around the balancer pipe joints. I also read somewhere one owner said that leaving the balance pipe clamp loose allowed the pipe to slide and alleviated the problem. The collector box can also be repaired and extra gussets added if required. However, I was a bit surprised how prone the system seems to be to cracking. Therefore, after repairing it enough to gain confidence that I liked the bike, I bought a Mistral header and collector assembly (purchased through Stein-Dinse Germany). Advantage was that the system does not have a balance pipe and that the collector is just a cross-over pipe under the gearbox. The whole system has more give and is therefore, less highly stressed. It is also nice as changing the gearbox oil is much easier. Disadvantage: the bikes fuelling was already not great and the new exhaust perhaps irritated the situation further (see ECU and remapping).